Re: [PATCH] mmc: meson-gx: add SDIO interrupt support

[Ulf Hansson <ulf.hansson@linaro.org>]

On Thu, 18 Aug 2022 at 08:20, Heiner Kallweit <hkallweit1@gmail.com> wrote:
>
> On 15.08.2022 20:20, Ulf Hansson wrote:
> > On Sun, 14 Aug 2022 at 23:44, Heiner Kallweit <hkallweit1@gmail.com> wrote:
> >>
> >> This adds SDIO interrupt support.
> >> Successfully tested on a S905X4-based system with a BRCM4334
> >> SDIO wifi module (brcmfmac driver).
> >>
> >> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> >> ---
> >>  drivers/mmc/host/meson-gx-mmc.c | 45 +++++++++++++++++++++++++--------
> >>  1 file changed, 34 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> >> index 2f08d442e..e8d53fcdd 100644
> >> --- a/drivers/mmc/host/meson-gx-mmc.c
> >> +++ b/drivers/mmc/host/meson-gx-mmc.c
> >> @@ -41,14 +41,17 @@
> >>  #define   CLK_V2_TX_DELAY_MASK GENMASK(19, 16)
> >>  #define   CLK_V2_RX_DELAY_MASK GENMASK(23, 20)
> >>  #define   CLK_V2_ALWAYS_ON BIT(24)
> >> +#define   CLK_V2_IRQ_SDIO_SLEEP BIT(29)
> >>
> >>  #define   CLK_V3_TX_DELAY_MASK GENMASK(21, 16)
> >>  #define   CLK_V3_RX_DELAY_MASK GENMASK(27, 22)
> >>  #define   CLK_V3_ALWAYS_ON BIT(28)
> >> +#define   CLK_V3_IRQ_SDIO_SLEEP BIT(29)
> >>
> >>  #define   CLK_TX_DELAY_MASK(h)         (h->data->tx_delay_mask)
> >>  #define   CLK_RX_DELAY_MASK(h)         (h->data->rx_delay_mask)
> >>  #define   CLK_ALWAYS_ON(h)             (h->data->always_on)
> >> +#define   CLK_IRQ_SDIO_SLEEP(h)                (h->data->irq_sdio_sleep)
> >>
> >>  #define SD_EMMC_DELAY 0x4
> >>  #define SD_EMMC_ADJUST 0x8
> >> @@ -100,9 +103,6 @@
> >>  #define   IRQ_END_OF_CHAIN BIT(13)
> >>  #define   IRQ_RESP_STATUS BIT(14)
> >>  #define   IRQ_SDIO BIT(15)
> >> -#define   IRQ_EN_MASK \
> >> -       (IRQ_CRC_ERR | IRQ_TIMEOUTS | IRQ_END_OF_CHAIN | IRQ_RESP_STATUS |\
> >> -        IRQ_SDIO)
> >>
> >>  #define SD_EMMC_CMD_CFG 0x50
> >>  #define SD_EMMC_CMD_ARG 0x54
> >> @@ -136,6 +136,7 @@ struct meson_mmc_data {
> >>         unsigned int rx_delay_mask;
> >>         unsigned int always_on;
> >>         unsigned int adjust;
> >> +       unsigned int irq_sdio_sleep;
> >>  };
> >>
> >>  struct sd_emmc_desc {
> >> @@ -431,6 +432,7 @@ static int meson_mmc_clk_init(struct meson_host *host)
> >>         clk_reg |= FIELD_PREP(CLK_CORE_PHASE_MASK, CLK_PHASE_180);
> >>         clk_reg |= FIELD_PREP(CLK_TX_PHASE_MASK, CLK_PHASE_0);
> >>         clk_reg |= FIELD_PREP(CLK_RX_PHASE_MASK, CLK_PHASE_0);
> >> +       clk_reg |= CLK_IRQ_SDIO_SLEEP(host);
> >>         writel(clk_reg, host->regs + SD_EMMC_CLOCK);
> >>
> >>         /* get the mux parents */
> >> @@ -933,7 +935,6 @@ static irqreturn_t meson_mmc_irq(int irq, void *dev_id)
> >>  {
> >>         struct meson_host *host = dev_id;
> >>         struct mmc_command *cmd;
> >> -       struct mmc_data *data;
> >>         u32 irq_en, status, raw_status;
> >>         irqreturn_t ret = IRQ_NONE;
> >>
> >> @@ -948,14 +949,24 @@ static irqreturn_t meson_mmc_irq(int irq, void *dev_id)
> >>                 return IRQ_NONE;
> >>         }
> >>
> >> -       if (WARN_ON(!host) || WARN_ON(!host->cmd))
> >> +       if (WARN_ON(!host))
> >>                 return IRQ_NONE;
> >>
> >>         /* ack all raised interrupts */
> >>         writel(status, host->regs + SD_EMMC_STATUS);
> >>
> >>         cmd = host->cmd;
> >> -       data = cmd->data;
> >> +
> >> +       if (status & IRQ_SDIO) {
> >> +               mmc_signal_sdio_irq(host->mmc);
> >
> > This is the legacy interface for supporting SDIO irqs. I am planning
> > to remove it, sooner or later.
> >
> > Please convert into using sdio_signal_irq() instead. Note that, using
> > sdio_signal_irq() means you need to implement support for
> > MMC_CAP2_SDIO_IRQ_NOTHREAD, which also includes to implement the
> > ->ack_sdio_irq() callback.
> >
> > There are other host drivers to be inspired from, but don't hesitate
> > to ask if there is something unclear.
> >
>
> One more question came to my mind:
>
> Typically host drivers disable the SDIO interrupt source before calling
> sdio_signal_irq(), and re-enable it in ->ack_sdio_irq().
>
> In sdio_run_irqs() we have the following:
>
> if (!host->sdio_irq_pending)
>         host->ops->ack_sdio_irq(host);
>
> In the middle of this code the host can't actively trigger a SDIO interrupt
> because the interrupt source is still disabled. But some other host interrupt
> could fire with also the SDIO interrupt source bit set.

It's the responsibility of the host driver to deal with this situation.

> Then the hard irq handler would disable the SDIO interrupt source, and directly
> after this ->ack_sdio_irq() would re-enable it.

The host driver shouldn't signal a new irq, before it has acked the
previous one via ->ack_sdio_irq().

> This looks racy to me and we may need some protection.
> Do you share this view or do I miss something?

The protection the mmc core provides around this, includes the general
host protection (mmc_claim|release_host()) in sdio_run_irqs() and by
using the workqueue of course.

Did that make sense?

Kind regards
Uffe

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