linux-kernel - Re: [PATCH 1/4] mmc: sdhci-omap: Fix DCRC error handling during tuning

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Date:   Wed, 21 Nov 2018 15:09:02 +0530
From:   Faiz Abbas <faiz_abbas@...com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        <linux-kernel@...r.kernel.org>, <linux-mmc@...r.kernel.org>
CC:     <ulf.hansson@...aro.org>, <adrian.hunter@...el.com>
Subject: Re: [PATCH 1/4] mmc: sdhci-omap: Fix DCRC error handling during
 tuning

Hi Kishon,

On 20/11/18 10:23 AM, Kishon Vijay Abraham I wrote:
> Hi,
> 
> On 19/11/18 4:46 PM, Faiz Abbas wrote:
>> Commit 7d33c3581536 ("mmc: sdhci-omap: Workaround for Errata i802")
>> disabled DCRC interrupts during tuning. This write to the interrupt
>> enable register gets overwritten in sdhci_prepare_data() and the
>> interrupt is not in fact disabled. Fix this by disabling the interrupt
>> in the host->ier variable.
>>
>> Signed-off-by: Faiz Abbas <faiz_abbas@...com>
>> ---
>>   drivers/mmc/host/sdhci-omap.c | 7 +++----
>>   1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci-omap.c
>> b/drivers/mmc/host/sdhci-omap.c
>> index 88347ce78f23..87138067e334 100644
>> --- a/drivers/mmc/host/sdhci-omap.c
>> +++ b/drivers/mmc/host/sdhci-omap.c
>> @@ -290,7 +290,6 @@ static int sdhci_omap_execute_tuning(struct
>> mmc_host *mmc, u32 opcode)
>>       u32 start_window = 0, max_window = 0;
>>       u8 cur_match, prev_match = 0;
>>       u32 length = 0, max_len = 0;
>> -    u32 ier = host->ier;
>>       u32 phase_delay = 0;
>>       int ret = 0;
>>       u32 reg;
>> @@ -317,9 +316,7 @@ static int sdhci_omap_execute_tuning(struct
>> mmc_host *mmc, u32 opcode)
>>        * during the tuning procedure. So disable it during the
>>        * tuning procedure.
>>        */
>> -    ier &= ~SDHCI_INT_DATA_CRC;
>> -    sdhci_writel(host, ier, SDHCI_INT_ENABLE);
>> -    sdhci_writel(host, ier, SDHCI_SIGNAL_ENABLE);
>> +    host->ier &= ~SDHCI_INT_DATA_CRC;
>>         while (phase_delay <= MAX_PHASE_DELAY) {
>>           sdhci_omap_set_dll(omap_host, phase_delay);
>> @@ -366,6 +363,8 @@ static int sdhci_omap_execute_tuning(struct
>> mmc_host *mmc, u32 opcode)
>>     ret:
>>       sdhci_reset(host, SDHCI_RESET_CMD | SDHCI_RESET_DATA);
>> +    /* Reenable forbidden interrupt */
>> +    host->ier |= SDHCI_INT_DATA_CRC;
> 
> It's better to have a backup of host->ier and restore the value here (in
> case DATA_CRC is disabled for other cases).
> 

host->ier is modified everywhere during an mmc request. I would not
expect it to hold its value after so many tuning commands. I can add a
bool to check of DCRC was enabled before and only then re-enable it.

Thanks,
Faiz