Re: [PATCH v2 2/2] mmc: meson-gx: add SDIO interrupt support

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

On Fri, 19 Aug 2022 at 23:14, Heiner Kallweit <hkallweit1@gmail.com> wrote:
>
> Add SDIO interrupt support. Successfully tested on a S905X4-based
> system (V3 register layout) with a BRCM4334 SDIO wifi module
> (brcmfmac driver). The implementation also considers the potential
> race discussed in [0].
>
> [0] https://lore.kernel.org/linux-arm-kernel/CAPDyKFoJDhjLkajBHgW3zHasvYYri77NQoDpiW-BpKgkdjtOyg@mail.gmail.com/
>
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
>  drivers/mmc/host/meson-gx-mmc.c | 76 ++++++++++++++++++++++++++++-----
>  1 file changed, 66 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> index 9a4da2544..58b7836a5 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(25)
>
>  #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
> @@ -135,6 +138,7 @@ 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 {
> @@ -174,6 +178,7 @@ struct meson_host {
>         bool vqmmc_enabled;
>         bool needs_pre_post_req;
>
> +       spinlock_t lock;
>  };
>
>  #define CMD_CFG_LENGTH_MASK GENMASK(8, 0)
> @@ -430,6 +435,7 @@ 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 */
> @@ -934,32 +940,54 @@ static void meson_mmc_read_resp(struct mmc_host *mmc, struct mmc_command *cmd)
>         }
>  }
>
> +static void __meson_mmc_enable_sdio_irq(struct mmc_host *mmc, int enable)
> +{
> +       struct meson_host *host = mmc_priv(mmc);
> +       u32 reg_irqen = IRQ_EN_MASK;
> +
> +       if (enable)
> +               reg_irqen |= IRQ_SDIO;
> +       writel(reg_irqen, host->regs + SD_EMMC_IRQ_EN);
> +}
> +
>  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 status, raw_status;
>         irqreturn_t ret = IRQ_NONE;
>
>         raw_status = readl(host->regs + SD_EMMC_STATUS);
> -       status = raw_status & IRQ_EN_MASK;
> +       status = raw_status & (IRQ_EN_MASK | IRQ_SDIO);
>
>         if (!status) {
>                 dev_dbg(host->dev,
>                         "Unexpected IRQ! irq_en 0x%08lx - status 0x%08x\n",
> -                        IRQ_EN_MASK, raw_status);
> +                        IRQ_EN_MASK | IRQ_SDIO, raw_status);
>                 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) {
> +               spin_lock(&host->lock);
> +               __meson_mmc_enable_sdio_irq(host->mmc, 0);
> +               sdio_signal_irq(host->mmc);
> +               spin_unlock(&host->lock);
> +               status &= ~IRQ_SDIO;
> +               if (!status)
> +                       return IRQ_HANDLED;
> +       }
> +
> +       if (WARN_ON(!cmd))
> +               return IRQ_NONE;
> +
>         cmd->error = 0;
>         if (status & IRQ_CRC_ERR) {
>                 dev_dbg(host->dev, "CRC Error - status 0x%08x\n", status);
> @@ -977,12 +1005,9 @@ static irqreturn_t meson_mmc_irq(int irq, void *dev_id)
>
>         meson_mmc_read_resp(host->mmc, cmd);
>
> -       if (status & IRQ_SDIO) {
> -               dev_dbg(host->dev, "IRQ: SDIO TODO.\n");
> -               ret = IRQ_HANDLED;
> -       }
> -
>         if (status & (IRQ_END_OF_CHAIN | IRQ_RESP_STATUS)) {
> +               struct mmc_data *data = cmd->data;
> +
>                 if (data && !cmd->error)
>                         data->bytes_xfered = data->blksz * data->blocks;
>                 if (meson_mmc_bounce_buf_read(data) ||
> @@ -1125,6 +1150,27 @@ static int meson_mmc_voltage_switch(struct mmc_host *mmc, struct mmc_ios *ios)
>         return -EINVAL;
>  }
>
> +static void meson_mmc_enable_sdio_irq(struct mmc_host *mmc, int enable)
> +{
> +       struct meson_host *host = mmc_priv(mmc);
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&host->lock, flags);
> +       __meson_mmc_enable_sdio_irq(mmc, enable);
> +       spin_unlock_irqrestore(&host->lock, flags);
> +}
> +
> +static void meson_mmc_ack_sdio_irq(struct mmc_host *mmc)
> +{
> +       struct meson_host *host = mmc_priv(mmc);
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&host->lock, flags);
> +       if (!mmc->sdio_irq_pending)

I am not quite sure I understand why you need to check this flag here.

The point is, in meson_mmc_irq() you are doing things in the correct
order, which means disabling the SDIO irq by calling
__meson_mmc_enable_sdio_irq(host->mmc, 0) prior calling
sdio_signal_irq(host->mmc) (which sets the flag).

In this way, the host driver should be prevented from signaling
another new SDIO irq, until it has acked (which means re-enabling the
SDIO irqs) the current one to be processed.

Or did I miss something?

> +               __meson_mmc_enable_sdio_irq(mmc, 1);
> +       spin_unlock_irqrestore(&host->lock, flags);
> +}
>

[...]

Other than the comment above, the patch looks good to me!

Kind regards
Uffe

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