Re: [PATCH V12 10/23] mmc: sdhci-uhs2: add reset function and uhs2_mode function

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

On 3/10/23 13:30, Ulf Hansson wrote:
> On Fri, 15 Sept 2023 at 11:44, Victor Shih <victorshihgli@gmail.com> wrote:
>>
>> From: Victor Shih <victor.shih@genesyslogic.com.tw>
>>
>> Sdhci_uhs2_reset() does a UHS-II specific reset operation.
>>
>> Signed-off-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
>> Signed-off-by: Victor Shih <victor.shih@genesyslogic.com.tw>
>> Acked-by: Adrian Hunter <adrian.hunter@intel.com>
>> ---
>>
>> Updates in V8:
>>  - Adjust the position of matching brackets.
>>
>> Updates in V6:
>>  - Remove unnecessary functions and simplify code.
>>
>> ---
>>
>>  drivers/mmc/host/sdhci-uhs2.c | 45 +++++++++++++++++++++++++++++++++++
>>  drivers/mmc/host/sdhci-uhs2.h |  2 ++
>>  2 files changed, 47 insertions(+)
>>
>> diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
>> index e339821d3504..dfc80a7f1bad 100644
>> --- a/drivers/mmc/host/sdhci-uhs2.c
>> +++ b/drivers/mmc/host/sdhci-uhs2.c
>> @@ -10,7 +10,9 @@
>>   *  Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
>>   */
>>
>> +#include <linux/delay.h>
>>  #include <linux/module.h>
>> +#include <linux/iopoll.h>
>>
>>  #include "sdhci.h"
>>  #include "sdhci-uhs2.h"
>> @@ -49,6 +51,49 @@ void sdhci_uhs2_dump_regs(struct sdhci_host *host)
>>  }
>>  EXPORT_SYMBOL_GPL(sdhci_uhs2_dump_regs);
>>
>> +/*****************************************************************************\
>> + *                                                                           *
>> + * Low level functions                                                       *
>> + *                                                                           *
>> +\*****************************************************************************/
>> +
>> +bool sdhci_uhs2_mode(struct sdhci_host *host)
>> +{
>> +       return host->mmc->flags & MMC_UHS2_SUPPORT;
> 
> The MMC_UHS2_SUPPORT bit looks redundant to me. Instead, I think we
> should be using mmc->ios.timings, which already indicates whether we
> are using UHS2 (MMC_TIMING_UHS2_SPEED_*). See patch2 where we added
> this.
> 
> That said, I think we should drop the sdhci_uhs2_mode() function
> altogether and instead use mmc_card_uhs2(), which means we should move
> it to include/linux/mmc/host.h, so it becomes available for host
> drivers.
> 

UHS2 mode starts at UHS2 initialization and ends either when UHS2
initialization fails, or the card is removed.

So it includes re-initialization and reset when the transfer mode
currently transitions through MMC_TIMING_LEGACY.

So mmc_card_uhs2() won't work correctly for the host callbacks
unless something is done about that.