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

Vijay Viswanath
2017-08-28T12:34:16Z

On 8/24/2017 1:12 PM, Adrian Hunter wrote:
> On 18/08/17 08:19, 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>
>> ---
>> 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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