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

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Date:   Mon, 28 Aug 2017 18:04:06 +0530
From:   Vijay Viswanath <vviswana@...eaurora.org>
To:     Adrian Hunter <adrian.hunter@...el.com>, ulf.hansson@...aro.org,
        will.deacon@....com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        asutoshd@...eaurora.org, stummala@...eaurora.org,
        riteshh@...eaurora.org, subhashj@...eaurora.org
Subject: Re: [PATCH 2/5] mmc: sdhci-msm: Fix HW issue with power IRQ handling
 during reset



On 8/24/2017 1:12 PM, Adrian Hunter wrote:
> On 18/08/17 08:19, Vijay Viswanath wrote:
>> From: Sahitya Tummala <stummala@...eaurora.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@...eaurora.org>
>> Signed-off-by: Vijay Viswanath <vviswana@...eaurora.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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