[PATCH v2 2/2] mmc: meson-gx: add SDIO interrupt support
Ulf Hansson
ulf.hansson at linaro.org
Wed Aug 24 05:57:14 PDT 2022
On Tue, 23 Aug 2022 at 20:16, Heiner Kallweit <hkallweit1 at gmail.com> wrote:
>
> On 22.08.2022 13:33, Ulf Hansson wrote:
> > On Fri, 19 Aug 2022 at 23:14, Heiner Kallweit <hkallweit1 at 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 at 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?
> >
>
> What could happen (at least based on the code):
> Even though SDIO IRQ signalling is disabled we may receive another
> interrupt that by chance has also the SDIO IRQ status bit set.
That sounds like a broken HW to me, but I get your point.
> And if the hard irq handler interrupts sdio_run_irqs() here then
> we may have a problem.
>
> if (!host->sdio_irq_pending)
> host->ops->ack_sdio_irq(host);
>
> Therefore the additional check (because checking the flag and calling
> __meson_mmc_enable_sdio_irq() is protected by the spinlock).
> However that's a theoretical worst case scenario. It don't know enough
> about SDIO interrupts to state whether it actually can happen.
If you are worried about getting spurious IRQs with the SDIO IRQ
status bit set, then I prefer that you use a meson host driver
specific flag. The flag could indicate whether the IRQ_SDIO bit has
been set in the IRQ_EN_MASK (__meson_mmc_enable_sdio_irq()) and then
simply prevent (or postpone) signaling a new SDIO IRQ
(sdio_signal_irq()).
>
> By the way: I'd also be reluctant to omit checking the SDIO IRQ status bit
> if host->sdio_irq_pending is true because then we might miss a SDIO interrupt.
Again, that sounds like a broken HW to me.
If you are worried that we may miss an SDIO irq, then it's seems
better to "cache" that additional SDIO IRQ in a state variable (from
the irq handler) and then check that variable in ->ack_sdio_irq() to
immediately signal a new SDIO irq (sdio_signal_irq()).
>
> But if you say it's not needed I'll remove the duplicated flag check.
Let me put it like this, if the HW works as expected, the additional
check/protection should not be needed. So in the end, this is your
call.
>
> >> + __meson_mmc_enable_sdio_irq(mmc, 1);
> >> + spin_unlock_irqrestore(&host->lock, flags);
> >> +}
> >>
[...]
Kind regards
Uffe
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