Re: [PATCH 2/5] mmc: sdhci-msm: Fix HW issue with power IRQ handling during reset

[Vijay Viswanath]

On 8/24/2017 1:12 PM, Adrian Hunter wrote:
> On 18/08/17 08:19, Vijay Viswanath wrote:
> > From: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>
> >
> > There is a rare scenario in HW, where the first clear pulse could
> > be lost when the actual reset and clear/read of status register
> > are happening at the same time. Fix this by retrying upto 10 times
> > to ensure the status register gets cleared. Otherwise, this will
> > lead to a spurious power IRQ which results in system instability.
> >
> > Signed-off-by: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>
> > Signed-off-by: Vijay Viswanath <vviswana@xxxxxxxxxxxxxx>
> > ---
> >   drivers/mmc/host/sdhci-msm.c | 43 ++++++++++++++++++++++++++++++++++++++++---
> >   1 file changed, 40 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> > index 0957199..f3e0489 100644
> > --- a/drivers/mmc/host/sdhci-msm.c
> > +++ b/drivers/mmc/host/sdhci-msm.c
> > @@ -995,17 +995,51 @@ static void sdhci_msm_set_uhs_signaling(struct sdhci_host *host,
> >   		sdhci_msm_hs400(host, &mmc->ios);
> >   }
> >   
> > -static void sdhci_msm_voltage_switch(struct sdhci_host *host)
> > +static void sdhci_msm_dump_pwr_ctrl_regs(struct sdhci_host *host)
> > +{
> > +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> > +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> > +
> > +	pr_err("%s: PWRCTL_STATUS: 0x%08x | PWRCTL_MASK: 0x%08x | PWRCTL_CTL: 0x%08x\n",
> > +			mmc_hostname(host->mmc),
> > +			readl_relaxed(msm_host->core_mem + CORE_PWRCTL_STATUS),
> > +			readl_relaxed(msm_host->core_mem + CORE_PWRCTL_MASK),
> > +			readl_relaxed(msm_host->core_mem + CORE_PWRCTL_CTL));
> > +}
> > +
> > +static void sdhci_msm_handle_pwr_irq(struct sdhci_host *host, int irq)
> >   {
> >   	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> >   	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> >   	u32 irq_status, irq_ack = 0;
> > +	int retry = 10;
> >   
> >   	irq_status = readl_relaxed(msm_host->core_mem + CORE_PWRCTL_STATUS);
> >   	irq_status &= INT_MASK;
> >   
> >   	writel_relaxed(irq_status, msm_host->core_mem + CORE_PWRCTL_CLEAR);
> >   
> > +	/*
> > +	 * There is a rare HW scenario where the first clear pulse could be
> > +	 * lost when actual reset and clear/read of status register is
> > +	 * happening at a time. Hence, retry for at least 10 times to make
> > +	 * sure status register is cleared. Otherwise, this will result in
> > +	 * a spurious power IRQ resulting in system instability.
> > +	 */
> > +	while (irq_status & readl_relaxed(msm_host->core_mem +
> > +				CORE_PWRCTL_STATUS)) {
> > +		if (retry == 0) {
> > +			pr_err("%s: Timedout clearing (0x%x) pwrctl status register\n",
> > +					mmc_hostname(host->mmc), irq_status);
> > +			sdhci_msm_dump_pwr_ctrl_regs(host);
> > +			WARN_ON(1);
>
> Is it your intention to loop forever here?
A bad mistake from my side. Will add break here.
> > +		}
> > +		writel_relaxed(irq_status,
> > +				msm_host->core_mem + CORE_PWRCTL_CLEAR);
> > +		retry--;
> > +		udelay(10);
> > +	}
> > +
> >   	if (irq_status & (CORE_PWRCTL_BUS_ON | CORE_PWRCTL_BUS_OFF))
> >   		irq_ack |= CORE_PWRCTL_BUS_SUCCESS;
> >   	if (irq_status & (CORE_PWRCTL_IO_LOW | CORE_PWRCTL_IO_HIGH))
> > @@ -1017,13 +1051,17 @@ static void sdhci_msm_voltage_switch(struct sdhci_host *host)
> >   	 * switches are handled by the sdhci core, so just report success.
> >   	 */
> >   	writel_relaxed(irq_ack, msm_host->core_mem + CORE_PWRCTL_CTL);
> > +
> > +	pr_debug("%s: %s: Handled IRQ(%d), irq_status=0x%x, ack=0x%x\n",
> > +		mmc_hostname(msm_host->mmc), __func__, irq, irq_status,
> > +		irq_ack);
> >   }
> >   
> >   static irqreturn_t sdhci_msm_pwr_irq(int irq, void *data)
> >   {
> >   	struct sdhci_host *host = (struct sdhci_host *)data;
> >   
> > -	sdhci_msm_voltage_switch(host);
> > +	sdhci_msm_handle_pwr_irq(host, irq);
> >   
> >   	return IRQ_HANDLED;
> >   }
> > @@ -1106,7 +1144,6 @@ static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
> >   	.get_max_clock = sdhci_msm_get_max_clock,
> >   	.set_bus_width = sdhci_set_bus_width,
> >   	.set_uhs_signaling = sdhci_msm_set_uhs_signaling,
> > -	.voltage_switch = sdhci_msm_voltage_switch,
> >   };
> >   
> >   static const struct sdhci_pltfm_data sdhci_msm_pdata = {
>
> --
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