Subject: [PATCHv2 2/2] mailbox: Adding driver for Xilinx LogiCORE IP mailbox.

From: [email-masked] (Michal Simek)
Date: Fri, 29 May 2015 07:44:00 +0200

On 05/28/2015 07:35 PM, Moritz Fischer wrote:
> On Wed, May 27, 2015 at 10:45 PM, Michal Simek <[email-masked]> wrote:
>> On 05/27/2015 08:35 PM, Moritz Fischer wrote:
>>> The Xilinx LogiCORE IP mailbox is a FPGA core that allows for
>>> interprocessor communication via AXI4 memory mapped / AXI4 stream
>>> interfaces.
>>>
>>> It is single channel per core and allows for transmit and receive.
>>>
>>> Changes from v1:
>>> - Added common clock framework support
>>> - Deal with IRQs that happend before driver load,
>>>   since HW will not let us know about them when we enable IRQs
>>>
>>> Changes from v0:
>>> - Several stylistic issues
>>> - Dropped superfluous intr_mode member
>>> - Really masking the IRQs on mailbox_shutdown
>>> - No longer using polling by accident in non-IRQ mode
>>> - Swapped doc and driver commits
>>>
>>> Signed-off-by: Moritz Fischer <[email-masked]>
>>> ---
>>>  MAINTAINERS                      |   7 +
>>>  drivers/mailbox/Kconfig          |   8 +
>>>  drivers/mailbox/Makefile         |   2 +
>>>  drivers/mailbox/mailbox-xilinx.c | 349 ++++++++++++++++++++++++++++++++++
>>>  4 files changed, 366 insertions(+)
>>>
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index f8e0afb..f1f0d10 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -10986,6 +10986,13 @@ M:   John Linn <[email-masked]>
>>>  S:   Maintained
>>>  F:   drivers/net/ethernet/xilinx/xilinx_axienet*
>>>
>>> +XILINX MAILBOX DRIVER
>>> +M:   Moritz Fischer <[email-masked]>
>>> +L:   linux-kernel at vger.kernel.org
>>> +S:   Maintained
>>> +F:   drivers/mailbox/mailbox-xilinx.c
>>> +F:   Documentation/devicetree/bindings/mailbox/xilinx-mailbox.txt
>>> +
>>>  XILINX UARTLITE SERIAL DRIVER
>>>  M:   Peter Korsgaard <[email-masked]>
>>>  L:   linux-serial at vger.kernel.org
>>> diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
>>> index 84b0a2d..e11e4b2 100644
>>> --- a/drivers/mailbox/Kconfig
>>> +++ b/drivers/mailbox/Kconfig
>>> @@ -60,4 +60,12 @@ config ALTERA_MBOX
>>>         An implementation of the Altera Mailbox soft core. It is used
>>>         to send message between processors. Say Y here if you want to use the
>>>         Altera mailbox support.
>>> +
>>> +config XILINX_MBOX
>>> +     tristate "Xilinx Mailbox"
>>> +     help
>>> +       An implementation of the Xilinx Mailbox soft core. It is used
>>> +       to send message between processors. Say Y here if you want to use the
>>> +       Xilinx mailbox support.
>>> +
>>>  endif
>>> diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
>>> index b18201e..d28a028 100644
>>> --- a/drivers/mailbox/Makefile
>>> +++ b/drivers/mailbox/Makefile
>>> @@ -11,3 +11,5 @@ obj-$(CONFIG_OMAP2PLUS_MBOX)        += omap-mailbox.o
>>>  obj-$(CONFIG_PCC)            += pcc.o
>>>
>>>  obj-$(CONFIG_ALTERA_MBOX)    += mailbox-altera.o
>>> +
>>> +obj-$(CONFIG_XILINX_MBOX)    += mailbox-xilinx.o
>>> diff --git a/drivers/mailbox/mailbox-xilinx.c b/drivers/mailbox/mailbox-xilinx.c
>>> new file mode 100644
>>> index 0000000..fd1cdf2
>>> --- /dev/null
>>> +++ b/drivers/mailbox/mailbox-xilinx.c
>>> @@ -0,0 +1,349 @@
>>> +/*
>>> + * Copyright (c) 2015, National Instruments Corp. All rights reserved.
>>> + *
>>> + * Driver for the Xilinx LogiCORE mailbox IP block
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License as published by
>>> + * the Free Software Foundation; version 2 of the License.
>>> + *
>>> + * This program is distributed in the hope that 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/clk.h>
>>> +#include <linux/device.h>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/io.h>
>>> +#include <linux/kernel.h>
>>> +#include <linux/mailbox_controller.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of.h>
>>> +#include <linux/platform_device.h>
>>> +
>>> +#define DRIVER_NAME "xilinx-mailbox"
>>> +
>>> +/* register offsets */
>>> +#define MAILBOX_REG_WRDATA   0x00
>>> +#define MAILBOX_REG_RDDATA   0x08
>>> +#define MAILBOX_REG_STATUS   0x10
>>> +#define MAILBOX_REG_ERROR    0x14
>>> +#define MAILBOX_REG_SIT      0x18
>>> +#define MAILBOX_REG_RIT      0x1c
>>> +#define MAILBOX_REG_IS       0x20
>>> +#define MAILBOX_REG_IE       0x24
>>> +#define MAILBOX_REG_IP       0x28
>>> +
>>> +/* status register */
>>> +#define STS_RTA      BIT(3)
>>> +#define STS_STA      BIT(2)
>>> +#define STS_FULL     BIT(1)
>>> +#define STS_EMPTY    BIT(0)
>>> +
>>> +/* error register */
>>> +#define ERR_FULL     BIT(1)
>>> +#define ERR_EMPTY    BIT(0)
>>> +
>>> +/* mailbox interrupt status register */
>>> +#define INT_STATUS_ERR       BIT(2)
>>> +#define INT_STATUS_RTI       BIT(1)
>>> +#define INT_STATUS_STI       BIT(0)
>>> +
>>> +/* mailbox interrupt enable register */
>>> +#define INT_ENABLE_ERR       BIT(2)
>>> +#define INT_ENABLE_RTI       BIT(1)
>>> +#define INT_ENABLE_STI       BIT(0)
>>> +
>>> +#define MBOX_POLLING_MS              5       /* polling interval 5ms */
>>> +
>>> +struct xilinx_mbox {
>>> +     int irq;
>>> +     void __iomem *mbox_base;
>>> +     struct clk *clk;
>>> +     struct device *dev;
>>> +     struct mbox_controller controller;
>>> +
>>> +     /* if the controller supports only RX polling mode */
>>> +     struct timer_list rxpoll_timer;
>>> +};
>>> +
>>> +static struct xilinx_mbox *mbox_chan_to_xilinx_mbox(struct mbox_chan *chan)
>>> +{
>>> +     if (!chan || !chan->con_priv)
>>> +             return NULL;
>>> +
>>> +     return (struct xilinx_mbox *)chan->con_priv;
>>> +}
>>> +
>>> +static inline bool xilinx_mbox_full(struct xilinx_mbox *mbox)
>>> +{
>>> +     u32 status;
>>> +
>>> +     status = readl_relaxed(mbox->mbox_base + MAILBOX_REG_STATUS);
>>> +
>>> +     return status & STS_FULL;
>>> +}
>>> +
>>> +static inline bool xilinx_mbox_pending(struct xilinx_mbox *mbox)
>>> +{
>>> +     u32 status;
>>> +
>>> +     status = readl_relaxed(mbox->mbox_base + MAILBOX_REG_STATUS);
>>> +
>>> +     return !(status & STS_EMPTY);
>>> +}
>>> +
>>> +static void xilinx_mbox_intmask(struct xilinx_mbox *mbox, u32 mask, bool enable)
>>> +{
>>> +     u32 mask_reg;
>>> +
>>> +     mask_reg = readl_relaxed(mbox->mbox_base + MAILBOX_REG_IE);
>>> +     if (enable)
>>> +             mask_reg |= mask;
>>> +     else
>>> +             mask_reg &= ~mask;
>>> +     writel_relaxed(mask_reg, mbox->mbox_base + MAILBOX_REG_IE);
>>> +}
>>> +
>>> +
>>> +static inline void xilinx_mbox_rx_intmask(struct xilinx_mbox *mbox, bool enable)
>>> +{
>>> +     xilinx_mbox_intmask(mbox, INT_ENABLE_RTI, enable);
>>> +}
>>> +
>>> +static inline void xilinx_mbox_tx_intmask(struct xilinx_mbox *mbox, bool enable)
>>> +{
>>> +     xilinx_mbox_intmask(mbox, INT_ENABLE_STI, enable);
>>> +}
>>> +
>>> +static void xilinx_mbox_rx_data(struct mbox_chan *chan)
>>> +{
>>> +     struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
>>> +     u32 data;
>>> +
>>> +     if (xilinx_mbox_pending(mbox)) {
>>> +             data = readl_relaxed(mbox->mbox_base + MAILBOX_REG_RDDATA);
>>> +             mbox_chan_received_data(chan, (void *)data);
>>> +     }
>>> +}
>>> +
>>> +static void xilinx_mbox_poll_rx(unsigned long data)
>>> +{
>>> +     struct mbox_chan *chan = (struct mbox_chan *)data;
>>> +     struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
>>> +
>>> +     xilinx_mbox_rx_data(chan);
>>> +
>>> +     mod_timer(&mbox->rxpoll_timer,
>>> +               jiffies + msecs_to_jiffies(MBOX_POLLING_MS));
>>> +}
>>> +
>>> +static irqreturn_t xilinx_mbox_interrupt(int irq, void *p)
>>> +{
>>> +     u32 mask;
>>> +     struct mbox_chan *chan = (struct mbox_chan *)p;
>>> +     struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
>>> +
>>> +     mask = readl_relaxed(mbox->mbox_base + MAILBOX_REG_IS);
>>> +     if (mask & INT_STATUS_RTI)
>>> +             xilinx_mbox_rx_data(chan);
>>> +
>>> +     /* mask irqs *before* notifying done, require tx_block=true */
>>> +     if (mask & INT_STATUS_STI) {
>>> +             xilinx_mbox_tx_intmask(mbox, false);
>>> +             mbox_chan_txdone(chan, 0);
>>> +     }
>>> +
>>> +     writel_relaxed(mask, mbox->mbox_base + MAILBOX_REG_IS);
>>
>> empty line here please.
> 
> Will do
>>> +     return IRQ_HANDLED;
>>> +}
>>> +
>>> +static int xilinx_mbox_startup(struct mbox_chan *chan)
>>> +{
>>> +     int ret;
>>> +     struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
>>> +
>>> +     if (mbox->irq >= 0) {
>>> +             ret = request_irq(mbox->irq, xilinx_mbox_interrupt, 0,
>>> +                               dev_name(mbox->dev), chan);
>>> +             if (unlikely(ret)) {
>>> +                     dev_err(mbox->dev,
>>> +                             "failed to register mailbox interrupt:%d\n",
>>> +                             ret);
>>> +                     goto polling; /* use polling if failed */
>>
>> This is the problematic path. For case that request_irq failed - you are
>> using polling mode but in shutdown below mbox_irq > 0 and you will
>> free_irq not call del_timer_sync.
>> I understand that you want to be smart here but it should be enough just
>> to return error here and you are done. But up2you I expect that this
>> path wasn't tested.
> 
> Yeah, trying to be smart will likely go wrong. I'm fine with returning ret here.
>>> +             }
>>> +
>>> +             xilinx_mbox_rx_intmask(mbox, true);
>>> +
>>> +             /* if fifo was full already, we didn't get an interrupt */
>>> +             while (xilinx_mbox_pending(mbox))
>>> +                     xilinx_mbox_rx_data(chan);
>>> +
>>> +             return 0;
>>> +     }
>>> +
>>> +polling:
>>> +     /* setup polling timer */
>>> +     setup_timer(&mbox->rxpoll_timer, xilinx_mbox_poll_rx,
>>> +                 (unsigned long)chan);
>>> +     mod_timer(&mbox->rxpoll_timer,
>>> +               jiffies + msecs_to_jiffies(MBOX_POLLING_MS));
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int xilinx_mbox_send_data(struct mbox_chan *chan, void *data)
>>> +{
>>> +     struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
>>> +     u32 *udata = (u32 *)data;
>>> +
>>> +     if (!mbox || !data)
>>> +             return -EINVAL;
>>> +
>>> +     if (xilinx_mbox_full(mbox))
>>> +             return -EBUSY;
>>> +
>>> +     /* enable interrupt before send */
>>> +     if (mbox->irq >= 0)
>>> +             xilinx_mbox_tx_intmask(mbox, true);
>>> +
>>> +     writel_relaxed(*udata, mbox->mbox_base + MAILBOX_REG_WRDATA);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static bool xilinx_mbox_last_tx_done(struct mbox_chan *chan)
>>> +{
>>> +     struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
>>> +
>>> +     /* return false if mailbox is full */
>>> +     return !xilinx_mbox_full(mbox);
>>> +}
>>> +
>>> +static bool xilinx_mbox_peek_data(struct mbox_chan *chan)
>>> +{
>>> +     struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
>>> +
>>> +     return xilinx_mbox_pending(mbox);
>>> +}
>>> +
>>> +static void xilinx_mbox_shutdown(struct mbox_chan *chan)
>>> +{
>>> +     struct xilinx_mbox *mbox = mbox_chan_to_xilinx_mbox(chan);
>>> +
>>> +     if (mbox->irq >= 0) {
>>
>> look below.
>>
>>> +             /* mask all interrupts */
>>> +             writel_relaxed(0, mbox->mbox_base + MAILBOX_REG_IE);
>>> +             free_irq(mbox->irq, chan);
>>> +     } else {
>>> +             del_timer_sync(&mbox->rxpoll_timer);
>>> +     }
>>> +}
>>> +
>>> +static struct mbox_chan_ops xilinx_mbox_ops = {
>>> +     .send_data = xilinx_mbox_send_data,
>>> +     .startup = xilinx_mbox_startup,
>>> +     .shutdown = xilinx_mbox_shutdown,
>>> +     .last_tx_done = xilinx_mbox_last_tx_done,
>>> +     .peek_data = xilinx_mbox_peek_data,
>>> +};
>>> +
>>> +static int xilinx_mbox_probe(struct platform_device *pdev)
>>> +{
>>> +     struct xilinx_mbox *mbox;
>>> +     struct resource *regs;
>>> +     struct mbox_chan *chans;
>>> +     int ret;
>>> +
>>> +     mbox = devm_kzalloc(&pdev->dev, sizeof(*mbox), GFP_KERNEL);
>>> +     if (!mbox)
>>> +             return -ENOMEM;
>>> +
>>> +     /* get clk and enable */
>>> +     mbox->clk = devm_clk_get(&pdev->dev, "mbox");
>>> +     clk_prepare_enable(mbox->clk);
>>
>> huh you should probably check error first before enabling.
>> Also if you call enable there, you should also call
>> clk_disable_unprepare when any error here happen.
>> Probably make sense to move this clock enabling below.
> 
> Ouch, good catch. The problem with moving the enable further down is,
> that reading the regs requires the clock to already be up and running.
> Suggestions?

just put it to the best suitable location and handle error path correctly.

Thanks,
Michal