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SubjectRe: [PATCH v1 2/5] mmc: sdhci-msm: Fix HW issue with power IRQ handling during reset
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On 30/08/17 15:51, Vijay Viswanath wrote:
> From: Sahitya Tummala <stummala@codeaurora.org>
>
> 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@codeaurora.org>
> Signed-off-by: Vijay Viswanath <vviswana@codeaurora.org>

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
> drivers/mmc/host/sdhci-msm.c | 46 ++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 42 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index d636251..42a65ab 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -995,17 +995,52 @@ 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);
> + break;
> + }
> + 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 +1052,17 @@ 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 +1145,6 @@ 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 = {
> @@ -1257,7 +1295,7 @@ static int sdhci_msm_probe(struct platform_device *pdev)
> * acknowledged. Otherwise power irq interrupt handler would be
> * fired prematurely.
> */
> - sdhci_msm_voltage_switch(host);
> + sdhci_msm_handle_pwr_irq(host, 0);
>
> /*
> * Ensure that above writes are propogated before interrupt enablement
>

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