Subject: [RFC PATCH v2 1/9] mailbox: Add Amlogic Meson Message-Handling-Unit

From: [email-masked] (Neil Armstrong)
Date: Tue, 28 Jun 2016 16:00:57 +0200

On 06/25/2016 07:50 PM, Jassi Brar wrote:
> -#define INTR_STAT_OFS  0x0
> -#define INTR_SET_OFS   0x8
> -#define INTR_CLR_OFS   0x10
> -
> -#define MHU_LP_OFFSET  0x0
> -#define MHU_HP_OFFSET  0x20
> -#define MHU_SEC_OFFSET 0x200
> -#define TX_REG_OFFSET  0x100
> +#define INTR_SET_OFS   0x0
> +#define INTR_STAT_OFS  0x4
> +#define INTR_CLR_OFS   0x8
> 
> -#define MHU_CHANS      3
> +#define MHU_LP_OFFSET  0x10
> +#define MHU_HP_OFFSET  0x1c
> +
> +#define TX_REG_OFFSET  0x24
> +
> +#define MHU_CHANS      2
> 
> ^^^^^^^^ this is precisely the difference if we ignore cosmetic
> differences. So the IP is essentially the same.

Well, no. The overall design is similar. but clearly it's a different IP.

> [snip]
> 
>> -------------------------------------------------------------------------------------------
>> From: Neil Armstrong <[email-masked]>
>> Subject: [PATCH] mailbox: arm_mhu: Add support for Amlogic Meson MHU
>>
> Is there some version of MHU specified anywhere in manuals? It seems
> weird Amlogic took the IP and only rearranged the registers. Maybe the
> order is specific to non-Amba version of the IP?  Lets call it that.

I think Amlogic took an early Juno platform release and re-implemented the
MHU using the same concept but following their design rules.

> 
>> To achieve this integration, add support for generic probe from amba
>> or platform.
>> Move all register offsets to a data structure passed in either amba id or
>> platform dt id match table.
>>
>> Signed-off-by: Neil Armstrong <[email-masked]>
>> ---
>>  drivers/mailbox/arm_mhu.c | 217 ++++++++++++++++++++++++++++++++++++++--------
>>  1 file changed, 181 insertions(+), 36 deletions(-)
>>
>> diff --git a/drivers/mailbox/arm_mhu.c b/drivers/mailbox/arm_mhu.c
>> index 99befa7..d7fb843 100644
>> --- a/drivers/mailbox/arm_mhu.c
>> +++ b/drivers/mailbox/arm_mhu.c
>> @@ -22,45 +22,68 @@
>>  #include <linux/io.h>
>>  #include <linux/module.h>
>>  #include <linux/amba/bus.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/platform_device.h>
>>  #include <linux/mailbox_controller.h>
>>
>> -#define INTR_STAT_OFS  0x0
>> -#define INTR_SET_OFS   0x8
>> -#define INTR_CLR_OFS   0x10
>> +#define MHU_INTR_STAT_OFS      0x0
>> +#define MHU_INTR_SET_OFS       0x8
>> +#define MHU_INTR_CLR_OFS       0x10
>>
>>  #define MHU_LP_OFFSET  0x0
>>  #define MHU_HP_OFFSET  0x20
>>  #define MHU_SEC_OFFSET 0x200
>> -#define TX_REG_OFFSET  0x100
>> +#define MHU_TX_REG_OFFSET      0x100
>>
>> -#define MHU_CHANS      3
>> +#define MESON_INTR_SET_OFS     0x0
>> +#define MESON_INTR_STAT_OFS    0x4
>> +#define MESON_INTR_CLR_OFS     0x8
>> +
>> +#define MESON_MHU_LP_OFFSET    0x10
>> +#define MESON_MHU_HP_OFFSET    0x1c
>> +#define MESON_MHU_TX_OFFSET    0x24
>> +
>> +#define MAX_MHU_CHANS  3
>>
> MHU_CHANS always 3 doesn't hurt. Lets keep it unchanged.
> 
>>  struct mhu_link {
>>         unsigned irq;
>> -       void __iomem *tx_reg;
>> -       void __iomem *rx_reg;
>> +       void __iomem *tx_stat_reg;
>> +       void __iomem *tx_set_reg;
>> +       void __iomem *tx_clr_reg;
>> +       void __iomem *rx_stat_reg;
>> +       void __iomem *rx_set_reg;
>> +       void __iomem *rx_clr_reg;
>>  };
> 
> Yeah, this is OK.
> 
> 
>>
>>  struct arm_mhu {
>>         void __iomem *base;
>> -       struct mhu_link mlink[MHU_CHANS];
>> -       struct mbox_chan chan[MHU_CHANS];
>> +       struct mhu_link mlink[MAX_MHU_CHANS];
>> +       struct mbox_chan chan[MAX_MHU_CHANS];
>>         struct mbox_controller mbox;
>>  };
> just leave it MHU_CHANS
> 
>>
>> +struct arm_mhu_data {
>> +       unsigned int channels;
>> +       int rx_offsets[MAX_MHU_CHANS];
>> +       int tx_offsets[MAX_MHU_CHANS];
>> +       unsigned int intr_stat_offs;
>> +       unsigned int intr_set_offs;
>> +       unsigned int intr_clr_offs;
>> +};
> This is unnecessary. Please remove it and code will be simpler -
> assign rx/tx_regs directly in probe.

I won't assume the platform driver is only for Amlogic, it does not
make sense.

> 
>> +
>>  static irqreturn_t mhu_rx_interrupt(int irq, void *p)
>>  {
>>         struct mbox_chan *chan = p;
>>         struct mhu_link *mlink = chan->con_priv;
>>         u32 val;
>>
>> -       val = readl_relaxed(mlink->rx_reg + INTR_STAT_OFS);
>> +       val = readl_relaxed(mlink->rx_stat_reg);
>>         if (!val)
>>                 return IRQ_NONE;
>>
>>         mbox_chan_received_data(chan, (void *)&val);
>>
>> -       writel_relaxed(val, mlink->rx_reg + INTR_CLR_OFS);
>> +       writel_relaxed(val, mlink->rx_clr_reg);
>>
>>         return IRQ_HANDLED;
>>  }
>> @@ -68,7 +91,7 @@ static irqreturn_t mhu_rx_interrupt(int irq, void *p)
>>  static bool mhu_last_tx_done(struct mbox_chan *chan)
>>  {
>>         struct mhu_link *mlink = chan->con_priv;
>> -       u32 val = readl_relaxed(mlink->tx_reg + INTR_STAT_OFS);
>> +       u32 val = readl_relaxed(mlink->tx_stat_reg);
>>
>>         return (val == 0);
>>  }
>> @@ -78,7 +101,7 @@ static int mhu_send_data(struct mbox_chan *chan, void *data)
>>         struct mhu_link *mlink = chan->con_priv;
>>         u32 *arg = data;
>>
>> -       writel_relaxed(*arg, mlink->tx_reg + INTR_SET_OFS);
>> +       writel_relaxed(*arg, mlink->tx_set_reg);
>>
>>         return 0;
>>  }
>> @@ -89,8 +112,8 @@ static int mhu_startup(struct mbox_chan *chan)
>>         u32 val;
>>         int ret;
>>
>> -       val = readl_relaxed(mlink->tx_reg + INTR_STAT_OFS);
>> -       writel_relaxed(val, mlink->tx_reg + INTR_CLR_OFS);
>> +       val = readl_relaxed(mlink->tx_stat_reg);
>> +       writel_relaxed(val, mlink->tx_clr_reg);
>>
>>         ret = request_irq(mlink->irq, mhu_rx_interrupt,
>>                           IRQF_SHARED, "mhu_link", chan);
>> @@ -117,52 +140,155 @@ static const struct mbox_chan_ops mhu_ops = {
>>         .last_tx_done = mhu_last_tx_done,
>>  };
>>
>> -static int mhu_probe(struct amba_device *adev, const struct amba_id *id)
>> +static struct arm_mhu_data arm_mhu_amba_data = {
>> +       .channels = 3,
>> +       .rx_offsets = {MHU_LP_OFFSET, MHU_HP_OFFSET, MHU_SEC_OFFSET},
>> +       .tx_offsets = {MHU_LP_OFFSET + MHU_TX_REG_OFFSET,
>> +                      MHU_HP_OFFSET + MHU_TX_REG_OFFSET,
>> +                      MHU_SEC_OFFSET + MHU_TX_REG_OFFSET},
>> +       .intr_stat_offs = MHU_INTR_STAT_OFS,
>> +       .intr_set_offs = MHU_INTR_SET_OFS,
>> +       .intr_clr_offs = MHU_INTR_CLR_OFS,
>> +};
>> +
>> +static const struct arm_mhu_data meson_mhu_data = {
>> +       .channels = 2,
>> +       .rx_offsets = {MESON_MHU_LP_OFFSET, MESON_MHU_HP_OFFSET},
>> +       .tx_offsets = {MESON_MHU_LP_OFFSET + MESON_MHU_TX_OFFSET,
>> +                      MESON_MHU_HP_OFFSET + MESON_MHU_TX_OFFSET},
>> +       .intr_stat_offs = MESON_INTR_STAT_OFS,
>> +       .intr_set_offs = MESON_INTR_SET_OFS,
>> +       .intr_clr_offs = MESON_INTR_CLR_OFS,
>> +};
>> +
> These could be directly set in amba vs platform probes ?

It does not make sense to assume the platform driver is only for
amlogic gxbb, it could match other vendors aswell.

The amba could force a single struct, but it's smarter to use the
same mechanism and associate the struct to an ID.

> Thanks.

My main question is : do you really want to transform this simple driver into
a dirty multi-bus generic mailbox driver ?
The meson_mhu is only 199 lines and this patch adds 181 lines to the arm_mhu driver.

I'll personally push to have two separate drivers here.

Thanks,
Neil