Re: [PATCH v2] mmc: sdhci: make sure SDHCI_CLOCK_CARD_EN bit sticks

[Adrian Hunter <adrian.hunter@intel.com>]

On 4/03/20 5:34 pm, Ulf Hansson wrote:
> On Wed, 19 Feb 2020 at 22:07, Jean-Francois Dagenais
> <jeff.dagenais@gmail.com> wrote:
>>
>> Regardless of the broken-cd quirk, when it silently doesn't stick,
>> no clock is applied to the bus lines, yet the code continues to
>> try to make CMDs and times out after 10 seconds for each. This
>> process can take up to a minute as mmc_rescan_try_freq tries the
>> different commands to discover the card.
>>
>> Short of changing sdhci_enable_clk's signature chain in all
>> dependent drivers, at least provide a hint that this might be the
>> problem. This will save tons of time for system integrators.
>>
>> Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
> 
> The change looks reasonable to me. However I would like to get an ack
> by Adrian before applying, as I may not have thought of all the
> consequences this change may have.
> 
> Kind regards
> Uffe
> 
> 
>> ---
>> Changes in v2:
>>  * removed redundant wmb()
>> ---
>>  drivers/mmc/host/sdhci.c | 14 ++++++++++++++
>>  1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index 63db84481dff..42a02d034fda 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -1894,6 +1894,20 @@ void sdhci_enable_clk(struct sdhci_host *host, u16 clk)
>>
>>         clk |= SDHCI_CLOCK_CARD_EN;
>>         sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
>> +
>> +       clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
>> +       if (clk & SDHCI_CLOCK_CARD_EN)
>> +               return;
>> +
>> +       /* The controller will clear this bit if card absent condition is

Please make the comment style consistent with the rest of sdhci.c e.g.

	/*
	 * The controller blah...
	 * blah ...
	 */

>> +        * detected. If card is indeed present, check platform configuration for
>> +        * how CD is reported to the SDHCI host controller. There may be an
>> +        * "assume present" mechanism in the platform registers, or your pin mux
>> +        * may be incorrect.
>> +        */
>> +       pr_err("%s: SDHCI_CLOCK_CARD_EN bit did not stick. Card absent?\n",
>> +               mmc_hostname(host->mmc));
>> +       sdhci_dumpregs(host);

The error message is ok, but for some controllers this could happen normally
if the card is removed suddenly, so let's not also do a register dump.

>>  }
>>  EXPORT_SYMBOL_GPL(sdhci_enable_clk);
>>
>> --
>> 2.25.0
>>