Subject: [PATCH V2 05/10] firmware: tegra: add BPMP support

From: [email-masked] (Sivaram Nair)
Date: Fri, 8 Jul 2016 13:19:43 -0700

On Thu, Jul 07, 2016 at 07:18:34PM +0900, Alexandre Courbot wrote:
> On Thu, Jul 7, 2016 at 5:17 PM, Joseph Lo <[email-masked]> wrote:
> > On 07/06/2016 07:39 PM, Alexandre Courbot wrote:
> >>
> >> Sorry, I will probably need to do several passes on this one to
> >> understand everything, but here is what I can say after a first look:
> >>
> >> On Tue, Jul 5, 2016 at 6:04 PM, Joseph Lo <[email-masked]> wrote:
> >>>
> >>> The Tegra BPMP (Boot and Power Management Processor) is designed for the
> >>> booting process handling, offloading the power management tasks and
> >>> some system control services from the CPU. It can be clock, DVFS,
> >>> thermal/EDP, power gating operation and system suspend/resume handling.
> >>> So the CPU and the drivers of these modules can base on the service that
> >>> the BPMP firmware driver provided to signal the event for the specific PM
> >>> action to BPMP and receive the status update from BPMP.
> >>>
> >>> Comparing to the ARM SCPI, the service provided by BPMP is message-based
> >>> communication but not method-based. The BPMP firmware driver provides the
> >>> send/receive service for the users, when the user concerns the response
> >>> time. If the user needs to get the event or update from the firmware, it
> >>> can request the MRQ service as well. The user needs to take care of the
> >>> message format, which we call BPMP ABI.
> >>>
> >>> The BPMP ABI defines the message format for different modules or usages.
> >>> For example, the clock operation needs an MRQ service code called
> >>> MRQ_CLK with specific message format which includes different sub
> >>> commands for various clock operations. This is the message format that
> >>> BPMP can recognize.
> >>>
> >>> So the user needs two things to initiate IPC between BPMP. Get the
> >>> service from the bpmp_ops structure and maintain the message format as
> >>> the BPMP ABI defined.
> >>>
> >>> Based-on-the-work-by:
> >>> Sivaram Nair <[email-masked]>
> >>>
> >>> Signed-off-by: Joseph Lo <[email-masked]>
> >>> ---
> >>> Changes in V2:
> >>> - None
> >>> ---
> >>>   drivers/firmware/tegra/Kconfig  |   12 +
> >>>   drivers/firmware/tegra/Makefile |    1 +
> >>>   drivers/firmware/tegra/bpmp.c   |  713 +++++++++++++++++
> >>>   include/soc/tegra/bpmp.h        |   29 +
> >>>   include/soc/tegra/bpmp_abi.h    | 1601
> >>> +++++++++++++++++++++++++++++++++++++++
> >>>   5 files changed, 2356 insertions(+)
> >>>   create mode 100644 drivers/firmware/tegra/bpmp.c
> >>>   create mode 100644 include/soc/tegra/bpmp.h
> >>>   create mode 100644 include/soc/tegra/bpmp_abi.h
> >>>
> >>> diff --git a/drivers/firmware/tegra/Kconfig
> >>> b/drivers/firmware/tegra/Kconfig
> >>> index 1fa3e4e136a5..ff2730d5c468 100644
> >>> --- a/drivers/firmware/tegra/Kconfig
> >>> +++ b/drivers/firmware/tegra/Kconfig
> >>> @@ -10,4 +10,16 @@ config TEGRA_IVC
> >>>            keeps the content is synchronization between host CPU and
> >>> remote
> >>>            processors.
> >>>
> >>> +config TEGRA_BPMP
> >>> +       bool "Tegra BPMP driver"
> >>> +       depends on ARCH_TEGRA && TEGRA_HSP_MBOX && TEGRA_IVC
> >>> +       help
> >>> +         BPMP (Boot and Power Management Processor) is designed to
> >>> off-loading
> >>
> >>
> >> s/off-loading/off-load
> >>
> >>> +         the PM functions which include clock/DVFS/thermal/power from
> >>> the CPU.
> >>> +         It needs HSP as the HW synchronization and notification module
> >>> and
> >>> +         IVC module as the message communication protocol.
> >>> +
> >>> +         This driver manages the IPC interface between host CPU and the
> >>> +         firmware running on BPMP.
> >>> +
> >>>   endmenu
> >>> diff --git a/drivers/firmware/tegra/Makefile
> >>> b/drivers/firmware/tegra/Makefile
> >>> index 92e2153e8173..e34a2f79e1ad 100644
> >>> --- a/drivers/firmware/tegra/Makefile
> >>> +++ b/drivers/firmware/tegra/Makefile
> >>> @@ -1 +1,2 @@
> >>> +obj-$(CONFIG_TEGRA_BPMP)       += bpmp.o
> >>>   obj-$(CONFIG_TEGRA_IVC)                += ivc.o
> >>> diff --git a/drivers/firmware/tegra/bpmp.c
> >>> b/drivers/firmware/tegra/bpmp.c
> >>> new file mode 100644
> >>> index 000000000000..24fda626610e
> >>> --- /dev/null
> >>> +++ b/drivers/firmware/tegra/bpmp.c
> >>> @@ -0,0 +1,713 @@
> >>> +/*
> >>> + * Copyright (c) 2016, NVIDIA CORPORATION.  All rights reserved.
> >>> + *
> >>> + * This program is free software; you can redistribute it and/or modify
> >>> it
> >>> + * under the terms and conditions of the GNU General Public License,
> >>> + * version 2, as published by the Free Software Foundation.
> >>> + *
> >>> + * This program is distributed in the hope it will be useful, but
> >>> WITHOUT
> >>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> >>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
> >>> for
> >>> + * more details.
> >>> + */
> >>> +
> >>> +#include <linux/mailbox_client.h>
> >>> +#include <linux/of.h>
> >>> +#include <linux/of_address.h>
> >>> +#include <linux/of_device.h>
> >>> +#include <linux/platform_device.h>
> >>> +#include <linux/semaphore.h>
> >>> +
> >>> +#include <soc/tegra/bpmp.h>
> >>> +#include <soc/tegra/bpmp_abi.h>
> >>> +#include <soc/tegra/ivc.h>
> >>> +
> >>> +#define BPMP_MSG_SZ            128
> >>> +#define BPMP_MSG_DATA_SZ       120
> >>> +
> >>> +#define __MRQ_ATTRS            0xff000000
> >>> +#define __MRQ_INDEX(id)                ((id) & ~__MRQ_ATTRS)
> >>> +
> >>> +#define DO_ACK                 BIT(0)
> >>> +#define RING_DOORBELL          BIT(1)
> >>> +
> >>> +struct tegra_bpmp_soc_data {
> >>> +       u32 ch_index;           /* channel index */
> >>> +       u32 thread_ch_index;    /* thread channel index */
> >>> +       u32 cpu_rx_ch_index;    /* CPU Rx channel index */
> >>> +       u32 nr_ch;              /* number of total channels */
> >>> +       u32 nr_thread_ch;       /* number of thread channels */
> >>> +       u32 ch_timeout;         /* channel timeout */
> >>> +       u32 thread_ch_timeout;  /* thread channel timeout */
> >>> +};
> >>
> >>
> >> With just these comments it is not clear what everything in this
> >> structure does. Maybe a file-level comment explaining how BPMP
> >> basically works and what the different channels are allocated to would
> >> help understanding the code.
> >
> >
> > We have two kinds of TX channels (channel & thread channel above) for the
> > BPMP clients (clock, thermal, reset, power mgmt control, etc.) to use.
> >
> > The channel means an atomic channel that could be used when the client needs
> > the response immediately. e.g. setting clock rate, re-parent the clock
> > source. Each CPUs have it's own atomic for the usage. The client can acquire
> > one of them, and the ch_index means the first channel they are able to use
> > in the channel array.
> >
> > The response of thread channel can be postponed later. And the client allows
> > getting the response after BPMP finished the service and response to them by
> > IRQ. The thread_ch_index means the same the first  channel that the clients
> > are available to use.
> >
> > And the CPU RX channel is designed for the client to register some specific
> > services (We call MRQ in the bpmp_abi.) listen to some update from the BPMP
> > firmware.
> >
> > Because we might have different numbers of these channels, using this
> > structure as the bpmp_soc_data to get different configuration according to
> > different SoC.
> 
> Thanks, that clarifies things. This explanation deserves to in the C
> file as well IMHO.
> 
> So IIUC the first 13 channels (6 bound to a specific CPU core and 7
> threaded, allocated dynamically) are all used to initiate a
> communication to the BPMP, while the cpu_rx channel is used as a sort
> of IRQ (hence the name MRQ). Is this correct? This would be valuable
> to state too. Maybe cpu_rx_ch_index can even be renamed to something
> like mrq_ch_index to stress that fact.
> 
> A few additional comments follow below as I did a second pass on the code.
> 
> >
> >
> >>
> >>> +
> >>> +struct channel_info {
> >>> +       u32 tch_free;
> >>> +       u32 tch_to_complete;
> >>> +       struct semaphore tch_sem;
> >>> +};
> >>> +
> >>> +struct mb_data {
> >>> +       s32 code;
> >>> +       s32 flags;
> >>> +       u8 data[BPMP_MSG_DATA_SZ];
> >>> +} __packed;
> >>> +
> >>> +struct channel_data {
> >>> +       struct mb_data *ib;
> >>> +       struct mb_data *ob;
> >>> +};
> >>> +
> >>> +struct mrq {
> >>> +       struct list_head list;
> >>> +       u32 mrq_code;
> >>> +       bpmp_mrq_handler handler;
> >>> +       void *data;
> >>> +};
> >>> +
> >>> +struct tegra_bpmp {
> >>> +       struct device *dev;
> >>> +       const struct tegra_bpmp_soc_data *soc_data;
> >>> +       void __iomem *tx_base;
> >>> +       void __iomem *rx_base;
> >>> +       struct mbox_client cl;
> >>> +       struct mbox_chan *chan;
> >>> +       struct ivc *ivc_channels;
> >>> +       struct channel_data *ch_area;
> >>> +       struct channel_info ch_info;
> >>> +       struct completion *ch_completion;
> >>> +       struct list_head mrq_list;
> >>> +       struct tegra_bpmp_ops *ops;
> >>> +       spinlock_t lock;
> >>> +       bool init_done;
> >>> +};
> >>> +
> >>> +static struct tegra_bpmp *bpmp;
> >>
> >>
> >> static? Ok, we only need one... for now. How about a private member in
> >> your ivc structure that allows you to retrieve the bpmp and going
> >> dynamic? This will require an extra argument in many functions, but is
> >> cleaner design IMHO.
> >
> >
> > IVC is designed as a generic IPC protocol among different modules (We have
> > not introduced some other usages of the IVC right now.). Maybe don't churn
> > some other stuff into IVC is better.
> 
> Anything is fine if you can get rid of that static.
> 
> >
> >>
> >>> +
> >>> +static int bpmp_get_thread_ch(int idx)
> >>> +{
> >>> +       return bpmp->soc_data->thread_ch_index + idx;
> >>> +}
> >>> +
> >>> +static int bpmp_get_thread_ch_index(int ch)
> >>> +{
> >>> +       if (ch < bpmp->soc_data->thread_ch_index ||
> >>> +           ch >= bpmp->soc_data->cpu_rx_ch_index)
> >>
> >>
> >> Shouldn't that be ch >= bpmp->soc_data->cpu_rx_ch_index +
> >> bpmp->soc_data->nr_thread_ch?
> >>
> >> Either rx_ch_index indicates the upper bound of the threaded channels,
> >> and in that case you don't need tegra_bpmp_soc_data::nr_thread_ch, or
> >> it can be anywhere else and you should use the correct member.
> >
> >
> > According the to the table below, we have 14 channels.
> > atomic ch: 0 ~ 5, 6 chanls
> > thread ch: 6 ~ 17, 7 chanls
> > CPU RX ch: 13 ~ 14, 2 chanls

Or, did you mean

thread ch: 6 -> 12 
cpu rx ch: 13 (1 channel)

> >
> > +static const struct tegra_bpmp_soc_data soc_data_tegra186 = {
> > +       .ch_index = 0,
> > +       .thread_ch_index = 6,
> > +       .cpu_rx_ch_index = 13,
> > +       .nr_ch = 14,
> > +       .nr_thread_ch = 7,
> > +       .ch_timeout = 60 * USEC_PER_SEC,
> > +       .thread_ch_timeout = 600 * USEC_PER_SEC,
> > +};
> >
> > We use the index to check channel violation and nr_thread_ch for other usage
> > to avoid redundant channel number calculation elsewhere.
> 
> Sorry, my comment had a mistake. I meant that
> 
>           ch >= bpmp->soc_data->cpu_rx_ch_index
> 
> Should maybe be
> 
>           ch >= bpmp->soc_data->cpu_rx_ch_index + bpmp->soc_data->nr_thread_ch

Or did you mean
	ch >= bpmp->soc_data->thread_ch_index + bpmp->soc_data->nr_thread_ch ?

> 
> According to the description you gave of these fields, there is no
> guarantee that cpu_rx_ch_index will always be the first channel after
> the threaded channels.

I second Alex's concerns. It would better not to depend on the
adjacency of the channels. Also I think this data should come from the
device tree.

> 
> >
> >
> >>
> >>> +               return -1;
> >>> +       return ch - bpmp->soc_data->thread_ch_index;
> >>> +}
> >>> +
> >>> +static int bpmp_get_ob_channel(void)
> >>> +{
> >>> +       return smp_processor_id() + bpmp->soc_data->ch_index;
> >>> +}
> >>> +
> >>> +static struct completion *bpmp_get_completion_obj(int ch)
> >>> +{
> >>> +       int i = bpmp_get_thread_ch_index(ch);
> >>> +
> >>> +       return i < 0 ? NULL : bpmp->ch_completion + i;
> >>> +}
> >>> +
> >>> +static int bpmp_valid_txfer(void *ob_data, int ob_sz, void *ib_data, int
> >>> ib_sz)
> >>> +{
> >>> +       return ob_sz >= 0 && ob_sz <= BPMP_MSG_DATA_SZ &&
> >>> +              ib_sz >= 0 && ib_sz <= BPMP_MSG_DATA_SZ &&
> >>> +              (!ob_sz || ob_data) && (!ib_sz || ib_data);
> >>> +}
> >>> +
> >>> +static bool bpmp_master_acked(int ch)
> >>> +{
> >>> +       struct ivc *ivc_chan;
> >>> +       void *frame;
> >>> +       bool ready;
> >>> +
> >>> +       ivc_chan = bpmp->ivc_channels + ch;
> >>> +       frame = tegra_ivc_read_get_next_frame(ivc_chan);
> >>> +       ready = !IS_ERR_OR_NULL(frame);
> >>> +       bpmp->ch_area[ch].ib = ready ? frame : NULL;
> >>> +
> >>> +       return ready;
> >>> +}
> >>> +
> >>> +static int bpmp_wait_ack(int ch)
> 
> Shouldn't this be bpmp_wait_master_ack ? Looking at the two next
> functions makes me think it should (or bpmp_wait_master_free should be
> renamed to bpmp_wait_free).
> 
> >>> +{
> >>> +       ktime_t t;
> >>> +
> >>> +       t = ns_to_ktime(local_clock());
> >>> +
> >>> +       do {
> >>> +               if (bpmp_master_acked(ch))
> >>> +                       return 0;
> >>> +       } while (ktime_us_delta(ns_to_ktime(local_clock()), t) <
> >>> +                bpmp->soc_data->ch_timeout);
> >>> +
> >>> +       return -ETIMEDOUT;
> >>> +}
> >>> +
> >>> +static bool bpmp_master_free(int ch)
> >>> +{
> >>> +       struct ivc *ivc_chan;
> >>> +       void *frame;
> >>> +       bool ready;
> >>> +
> >>> +       ivc_chan = bpmp->ivc_channels + ch;
> >>> +       frame = tegra_ivc_write_get_next_frame(ivc_chan);
> >>> +       ready = !IS_ERR_OR_NULL(frame);
> >>> +       bpmp->ch_area[ch].ob = ready ? frame : NULL;
> >>> +
> >>> +       return ready;
> >>> +}
> >>> +
> >>> +static int bpmp_wait_master_free(int ch)
> >>> +{
> >>> +       ktime_t t;
> >>> +
> >>> +       t = ns_to_ktime(local_clock());
> >>> +
> >>> +       do {
> >>> +               if (bpmp_master_free(ch))
> >>> +                       return 0;
> >>> +       } while (ktime_us_delta(ns_to_ktime(local_clock()), t)
> >>> +                < bpmp->soc_data->ch_timeout);
> >>> +
> >>> +       return -ETIMEDOUT;
> >>> +}
> >>> +
> >>> +static int __read_ch(int ch, void *data, int sz)
> >>> +{
> >>> +       struct ivc *ivc_chan;
> >>> +       struct mb_data *p;
> >>> +
> >>> +       ivc_chan = bpmp->ivc_channels + ch;
> >>> +       p = bpmp->ch_area[ch].ib;
> >>> +       if (data)
> >>> +               memcpy_fromio(data, p->data, sz);
> >>> +
> >>> +       return tegra_ivc_read_advance(ivc_chan);
> >>> +}
> >>> +
> >>> +static int bpmp_read_ch(int ch, void *data, int sz)
> 
> bpmp_read_threaded_ch maybe? we have bpmp_write_threaded_ch below, as
> this function is clearly dealing with threaded channels only.
> 
> >>> +{
> >>> +       unsigned long flags;
> >>> +       int i, ret;
> >>> +
> >>> +       i = bpmp_get_thread_ch_index(ch);
> >>
> >>
> >> i is not a very good name for this variable.
> >> Also note that bpmp_get_thread_ch_index() can return -1, this case is
> >> not handled.
> >
> > Okay, will fix this.
> >
> >
> >>
> >>> +
> >>> +       spin_lock_irqsave(&bpmp->lock, flags);
> >>> +       ret = __read_ch(ch, data, sz);
> >>> +       bpmp->ch_info.tch_free |= (1 << i);
> >>> +       spin_unlock_irqrestore(&bpmp->lock, flags);
> >>> +
> >>> +       up(&bpmp->ch_info.tch_sem);
> >>> +
> >>> +       return ret;
> >>> +}
> >>> +
> >>> +static int __write_ch(int ch, int mrq_code, int flags, void *data, int
> >>> sz)
> >>> +{
> >>> +       struct ivc *ivc_chan;
> >>> +       struct mb_data *p;
> >>> +
> >>> +       ivc_chan = bpmp->ivc_channels + ch;
> >>> +       p = bpmp->ch_area[ch].ob;
> >>> +
> >>> +       p->code = mrq_code;
> >>> +       p->flags = flags;
> >>> +       if (data)
> >>> +               memcpy_toio(p->data, data, sz);
> >>> +
> >>> +       return tegra_ivc_write_advance(ivc_chan);
> >>> +}
> >>> +
> >>> +static int bpmp_write_threaded_ch(int *ch, int mrq_code, void *data, int
> >>> sz)
> >>> +{
> >>> +       unsigned long flags;
> >>> +       int ret, i;
> >>> +
> >>> +       ret = down_timeout(&bpmp->ch_info.tch_sem,
> >>> +
> >>> usecs_to_jiffies(bpmp->soc_data->thread_ch_timeout));
> >>> +       if (ret)
> >>> +               return ret;
> >>> +
> >>> +       spin_lock_irqsave(&bpmp->lock, flags);
> >>> +
> >>> +       i = __ffs(bpmp->ch_info.tch_free);
> >>> +       *ch = bpmp_get_thread_ch(i);
> >>> +       ret = bpmp_master_free(*ch) ? 0 : -EFAULT;
> >>> +       if (!ret) {
> 
> Style nit: I prefer to make the error case the exception, and normal
> runtime the norm. This is where a goto statement can actually make
> your code easier to follow. Have an err: label before the spin_unlock,
> and jump to it if ret != 0. Then you can have the next three lines at
> the lower indentation level, and not looking like as if they were an
> error themselves.
> 
> Or if you really don't like the goto, check for ret != 0 and do the
> spin_unlock and return in that block.
> 
> >>> +               bpmp->ch_info.tch_free &= ~(1 << i);
> >>> +               __write_ch(*ch, mrq_code, DO_ACK | RING_DOORBELL, data,
> >>> sz);
> >>> +               bpmp->ch_info.tch_to_complete |= (1 << *ch);
> >>> +       }
> >>> +
> >>> +       spin_unlock_irqrestore(&bpmp->lock, flags);
> >>> +
> >>> +       return ret;
> >>> +}
> >>> +
> >>> +static int bpmp_write_ch(int ch, int mrq_code, int flags, void *data,
> >>> int sz)
> >>> +{
> >>> +       int ret;
> >>> +
> >>> +       ret = bpmp_wait_master_free(ch);
> >>> +       if (ret)
> >>> +               return ret;
> >>> +
> >>> +       return __write_ch(ch, mrq_code, flags, data, sz);
> >>> +}
> >>> +
> >>> +static int bpmp_send_receive_atomic(int mrq_code, void *ob_data, int
> >>> ob_sz,
> >>> +                                   void *ib_data, int ib_sz)
> >>> +{
> >>> +       int ch, ret;
> >>> +
> >>> +       if (WARN_ON(!irqs_disabled()))
> >>> +               return -EPERM;
> >>> +
> >>> +       if (!bpmp_valid_txfer(ob_data, ob_sz, ib_data, ib_sz))
> >>> +               return -EINVAL;
> >>> +
> >>> +       if (!bpmp->init_done)
> >>> +               return -ENODEV;
> >>> +
> >>> +       ch = bpmp_get_ob_channel();
> >>> +       ret = bpmp_write_ch(ch, mrq_code, DO_ACK, ob_data, ob_sz);
> >>> +       if (ret)
> >>> +               return ret;
> >>> +
> >>> +       ret = mbox_send_message(bpmp->chan, NULL);
> >>> +       if (ret < 0)
> >>> +               return ret;
> >>> +       mbox_client_txdone(bpmp->chan, 0);
> >>> +
> >>> +       ret = bpmp_wait_ack(ch);
> >>> +       if (ret)
> >>> +               return ret;
> >>> +
> >>> +       return __read_ch(ch, ib_data, ib_sz);
> >>> +}
> >>> +
> >>> +static int bpmp_send_receive(int mrq_code, void *ob_data, int ob_sz,
> >>> +                            void *ib_data, int ib_sz)
> >>> +{
> >>> +       struct completion *comp_obj;
> >>> +       unsigned long timeout;
> >>> +       int ch, ret;
> >>> +
> >>> +       if (WARN_ON(irqs_disabled()))
> >>> +               return -EPERM;
> >>> +
> >>> +       if (!bpmp_valid_txfer(ob_data, ob_sz, ib_data, ib_sz))
> >>> +               return -EINVAL;
> >>> +
> >>> +       if (!bpmp->init_done)
> >>> +               return -ENODEV;
> >>> +
> >>> +       ret = bpmp_write_threaded_ch(&ch, mrq_code, ob_data, ob_sz);
> >>> +       if (ret)
> >>> +               return ret;
> >>> +
> >>> +       ret = mbox_send_message(bpmp->chan, NULL);
> >>> +       if (ret < 0)
> >>> +               return ret;
> >>> +       mbox_client_txdone(bpmp->chan, 0);
> >>> +
> >>> +       comp_obj = bpmp_get_completion_obj(ch);
> >>> +       timeout = usecs_to_jiffies(bpmp->soc_data->thread_ch_timeout);
> >>> +       if (!wait_for_completion_timeout(comp_obj, timeout))
> >>> +               return -ETIMEDOUT;
> >>> +
> >>> +       return bpmp_read_ch(ch, ib_data, ib_sz);
> >>> +}
> >>> +
> >>> +static struct mrq *bpmp_find_mrq(u32 mrq_code)
> >>> +{
> >>> +       struct mrq *mrq;
> >>> +
> >>> +       list_for_each_entry(mrq, &bpmp->mrq_list, list) {
> >>> +               if (mrq_code == mrq->mrq_code)
> >>> +                       return mrq;
> >>> +       }
> >>> +
> >>> +       return NULL;
> >>> +}
> >>> +
> >>> +static void bpmp_mrq_return_data(int ch, int code, void *data, int sz)
> >>> +{
> >>> +       int flags = bpmp->ch_area[ch].ib->flags;
> >>> +       struct ivc *ivc_chan;
> >>> +       struct mb_data *frame;
> >>> +       int ret;
> >>> +
> >>> +       if (WARN_ON(sz > BPMP_MSG_DATA_SZ))
> >>> +               return;
> >>> +
> >>> +       ivc_chan = bpmp->ivc_channels + ch;
> >>> +       ret = tegra_ivc_read_advance(ivc_chan);
> >>> +       WARN_ON(ret);
> >>> +
> >>> +       if (!(flags & DO_ACK))
> >>> +               return;
> >>> +
> >>> +       frame = tegra_ivc_write_get_next_frame(ivc_chan);
> >>> +       if (IS_ERR_OR_NULL(frame)) {
> >>> +               WARN_ON(1);
> >>> +               return;
> >>> +       }
> >>> +
> >>> +       frame->code = code;
> >>> +       if (data != NULL)
> >>> +               memcpy_toio(frame->data, data, sz);
> >>> +       ret = tegra_ivc_write_advance(ivc_chan);
> >>> +       WARN_ON(ret);
> >>> +
> >>> +       if (flags & RING_DOORBELL) {
> >>> +               ret = mbox_send_message(bpmp->chan, NULL);
> >>> +               if (ret < 0) {
> >>> +                       WARN_ON(1);
> >>> +                       return;
> >>> +               }
> >>> +               mbox_client_txdone(bpmp->chan, 0);
> >>> +       }
> >>> +}
> >>> +
> >>> +static void bpmp_mail_return(int ch, int ret_code, int val)
> >>> +{
> >>> +       bpmp_mrq_return_data(ch, ret_code, &val, sizeof(val));
> >>> +}
> >>> +
> >>> +static void bpmp_handle_mrq(int mrq_code, int ch)
> >>> +{
> >>> +       struct mrq *mrq;
> >>> +
> >>> +       spin_lock(&bpmp->lock);
> >>> +
> >>> +       mrq = bpmp_find_mrq(mrq_code);
> >>> +       if (!mrq) {
> >>> +               spin_unlock(&bpmp->lock);
> >>> +               bpmp_mail_return(ch, -EINVAL, 0);
> >>> +               return;
> >>> +       }
> >>> +
> >>> +       mrq->handler(mrq_code, mrq->data, ch);
> >>> +
> >>> +       spin_unlock(&bpmp->lock);
> >>> +}
> >>> +
> >>> +static int bpmp_request_mrq(int mrq_code, bpmp_mrq_handler handler, void
> >>> *data)
> >>> +{
> >>> +       struct mrq *mrq;
> >>> +       unsigned long flags;
> >>> +
> >>> +       if (!handler)
> >>> +               return -EINVAL;
> >>> +
> >>> +       mrq = devm_kzalloc(bpmp->dev, sizeof(*mrq), GFP_KERNEL);
> >>> +       if (!mrq)
> >>> +               return -ENOMEM;
> >>> +
> >>> +       spin_lock_irqsave(&bpmp->lock, flags);
> >>> +
> >>> +       mrq->mrq_code = __MRQ_INDEX(mrq_code);
> >>> +       mrq->handler = handler;
> >>> +       mrq->data = data;
> >>> +       list_add(&mrq->list, &bpmp->mrq_list);
> >>> +
> >>> +       spin_unlock_irqrestore(&bpmp->lock, flags);
> >>> +
> >>> +       return 0;
> >>> +}
> >>> +
> >>> +static void bpmp_mrq_handle_ping(int mrq_code, void *data, int ch)
> >>> +{
> >>> +       int challenge;
> >>> +       int reply;
> >>> +
> >>> +       challenge = *(int *)bpmp->ch_area[ch].ib->data;
> >>> +       reply = challenge << (smp_processor_id() + 1);
> >>> +       bpmp_mail_return(ch, 0, reply);
> >>> +}
> >>> +
> >>> +static int bpmp_mailman_init(void)
> >>> +{
> >>> +       return bpmp_request_mrq(MRQ_PING, bpmp_mrq_handle_ping, NULL);
> >>> +}
> >>> +
> >>> +static int bpmp_ping(void)
> >>> +{
> >>> +       unsigned long flags;
> >>> +       ktime_t t;
> >>> +       int challenge = 1;
> >>
> >>
> >> Mmmm, shouldn't use a mrq_ping_request instead of an parameter which
> >> size may vary depending on the architecture? On a 64-bit big endian
> >> architecture, your messages would be corrupted.
> >
> >
> > Clarify one thig first. The mrq_ping_request and mrq_handle_ping above are
> > used for the ping form BPMP to CPU. Like I said above, it's among CPU RX
> > channel to get some information from BPMP firmware.
> 
> Ok, so mrq_handle_ping *should* use these data structures at the very least.
> 
> >
> > Here is the ping request from CPU to BPMP to make sure we can IPC with BPMP
> > during the probe stage.
> >
> > About the endian issue, I think we don't consider that in the message format
> > right now. So I think we only support little endian for the IPC messages
> > right now.
> 
> Any code in the kernel should function correctly regardless of
> endianness. And the problem is not so much with endianness as it is
> with the operand size - is the BPMP expecting a 64-bit challenge here?
> Considering that the equivalent MRQ uses a 32-bit integer, I'd bet
> not. So please use u32/u64 as needed as well as cpu_to_leXX (and
> leXX_to_cpu for the opposite) to make your code solid.

I second this.

> 
> I understand that you don't want to use the MRQ structures because we
> are not handling a MRQ here, but if they are relevant I think this
> would still be safer that constructing messages from scalar data. That
> or we should introduce a proper structure for these messages, but here
> using the MRQ structure looks acceptable to me. Maybe they should not
> be named MRQ at all, but that's not for us to decide.

We should be using the mrq request structures from the ABI header.

> 
> >
> >>
> >>> +       int reply = 0;
> >>
> >>
> >> And this should probably be a mrq_ping_response. These remarks may
> >> also apply to bpmp_mrq_handle_ping().
> >
> > That is for receiving the ping request from BPMP.
> >
> >>
> >>> +       int ret;
> >>> +
> >>> +       t = ktime_get();
> >>> +       local_irq_save(flags);
> >>> +       ret = bpmp_send_receive_atomic(MRQ_PING, &challenge,
> >>> sizeof(challenge),
> >>> +                                      &reply, sizeof(reply));
> >>> +       local_irq_restore(flags);
> >>> +       t = ktime_sub(ktime_get(), t);
> >>> +
> >>> +       if (!ret)
> >>> +               dev_info(bpmp->dev,
> >>> +                        "ping ok: challenge: %d, reply: %d, time:
> >>> %lld\n",
> >>> +                        challenge, reply, ktime_to_us(t));
> >>> +
> >>> +       return ret;
> >>> +}
> >>> +
> >>> +static int bpmp_get_fwtag(void)
> >>> +{
> >>> +       unsigned long flags;
> >>> +       void *vaddr;
> >>> +       dma_addr_t paddr;
> >>> +       u32 addr;
> >>
> >>
> >> Here also we should use a mrq_query_tag_request.
> >
> > The is one-way request from CPU to BPMP. So we don't request an MRQ for
> > that.

It is not clear to me what you mean by 'one-way request' here. We are
sending a request to get the tag and we are getting the tag back via the
same message's response. Anyway, we should be using the 'struct
mrq_query_tag_request' here to be consistent.

> >
> >>
> >>> +       int ret;
> >>> +
> >>> +       vaddr = dma_alloc_coherent(bpmp->dev, BPMP_MSG_DATA_SZ, &paddr,
> >>> +                                  GFP_KERNEL);
> >>
> >>
> >> dma_addr_t may be 64 bit here, and you may get an address higher than
> >> the 32 bits allowed by mrq_query_tag_request! I guess you want to add
> >> GFP_DMA32 as flag to your call to dma_alloc_coherent.
> >
> > BPMP should able to handle the address above 32 bits, but I am not sure does
> > it configure to support that?

Either way, since this specific MRQ takes in only 32 bit address, I
think we should follow Alex's recommendation to use the GFP_DMA32 flag.

> 
> If the message you pass only contains a 32-bit address, then I'm
> afraid the protocol is the limiting factor here until it is updated.
> 
> Can't wait for the day when we will have to manage several versions of
> this protocol! >_<

If we need to pass a larger-than-32 bit address for this MRQ (or for
anything that takes in a 32-bit address now), the agreed upon process is
to define a new MRQ (i.e one with a different integer id) that takes in
new address type (and deprecating the 32-bit MRQ version). 

> 
> >
> > Will fix this.
> >
> >
> >>
> >>> +       if (!vaddr)
> >>> +               return -ENOMEM;
> >>> +       addr = paddr;
> >>> +
> >>> +       local_irq_save(flags);
> >>> +       ret = bpmp_send_receive_atomic(MRQ_QUERY_TAG, &addr,
> >>> sizeof(addr),
> >>> +                                      NULL, 0);
> >>> +       local_irq_restore(flags);
> >>> +
> >>> +       if (!ret)
> >>> +               dev_info(bpmp->dev, "fwtag: %s\n", (char *)vaddr);
> >>> +
> >>> +       dma_free_coherent(bpmp->dev, BPMP_MSG_DATA_SZ, vaddr, paddr);
> >>> +
> >>> +       return ret;
> >>> +}
> >>> +
> >>> +static void bpmp_signal_thread(int ch)
> >>> +{
> >>> +       int flags = bpmp->ch_area[ch].ob->flags;
> >>> +       struct completion *comp_obj;
> >>> +
> >>> +       if (!(flags & RING_DOORBELL))
> >>> +               return;
> >>> +
> >>> +       comp_obj = bpmp_get_completion_obj(ch);
> >>> +       if (!comp_obj) {
> >>> +               WARN_ON(1);
> >>> +               return;
> >>> +       }
> >>> +
> >>> +       complete(comp_obj);
> >>> +}
> >>> +
> >>> +static void bpmp_handle_rx(struct mbox_client *cl, void *data)
> >>> +{
> >>> +       int i, rx_ch;
> >>> +
> >>> +       rx_ch = bpmp->soc_data->cpu_rx_ch_index;
> >>> +
> >>> +       if (bpmp_master_acked(rx_ch))
> >>> +               bpmp_handle_mrq(bpmp->ch_area[rx_ch].ib->code, rx_ch);
> >>> +
> >>> +       spin_lock(&bpmp->lock);
> >>> +
> >>> +       for (i = 0; i < bpmp->soc_data->nr_thread_ch &&
> >>> +                       bpmp->ch_info.tch_to_complete; i++) {
> 
> for_each_set_bit(bpmp->ch_info.tch_to_complete, &i,
> bpmp->soc_data->nr_thread_ch) ?
> 
> This will reduce the number of iterations and you won't have to do the
> bpmp->ch_info.tch_to_complete & (1 << ch) check below.
> 
> >>> +               int ch = bpmp_get_thread_ch(i);
> >>> +
> >>> +               if ((bpmp->ch_info.tch_to_complete & (1 << ch)) &&
> >>> +                   bpmp_master_acked(ch)) {
> >>> +                       bpmp->ch_info.tch_to_complete &= ~(1 << ch);
> >>> +                       bpmp_signal_thread(ch);
> >>> +               }
> >>> +       }
> >>> +
> >>> +       spin_unlock(&bpmp->lock);
> >>> +}
> >>> +
> >>> +static void bpmp_ivc_notify(struct ivc *ivc)
> >>> +{
> >>> +       int ret;
> >>> +
> >>> +       ret = mbox_send_message(bpmp->chan, NULL);
> >>> +       if (ret < 0)
> >>> +               return;
> >>> +
> >>> +       mbox_send_message(bpmp->chan, NULL);
> >>
> >>
> >> Why the second call to mbox_send_message? May to useful to add a
> >> comment explaining it.
> >
> > Ah!! It should be mbox_client_txdone(). Good catch.
> 
> That makes more sense. :) But did this code work even with that typo?

It should have --- mbox_client_txdone() essentilly does nothing now.