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

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

On 4/10/23 11:35, Ulf Hansson wrote:
> On Tue, 3 Oct 2023 at 17:03, Adrian Hunter <adrian.hunter@intel.com> wrote:
>>
>> On 3/10/23 15:22, Ulf Hansson wrote:
>>> On Tue, 3 Oct 2023 at 13:37, Adrian Hunter <adrian.hunter@intel.com> wrote:
>>>>
>>>> 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.
>>>
>>> Right, thanks for clarifying!
>>>
>>> In that case I wonder if we couldn't change the way we update the
>>> ->ios.timing for UHS2. It seems silly to have two (similar) ways to
>>> indicate that we have moved to UHS2.
>>
>> Perhaps something like below:
>>
>> diff --git a/drivers/mmc/core/sd_uhs2.c b/drivers/mmc/core/sd_uhs2.c
>> index aacefdd6bc9e..e39d63d46041 100644
>> --- a/drivers/mmc/core/sd_uhs2.c
>> +++ b/drivers/mmc/core/sd_uhs2.c
>> @@ -70,7 +70,8 @@ static int sd_uhs2_power_off(struct mmc_host *host)
>>
>>         host->ios.vdd = 0;
>>         host->ios.clock = 0;
>> -       host->ios.timing = MMC_TIMING_LEGACY;
>> +       /* Must set UHS2 timing to identify UHS2 mode */
>> +       host->ios.timing = MMC_TIMING_UHS2_SPEED_A;
>>         host->ios.power_mode = MMC_POWER_OFF;
>>         if (host->flags & MMC_UHS2_SD_TRAN)
>>                 host->flags &= ~MMC_UHS2_SD_TRAN;
>> @@ -1095,7 +1096,8 @@ static void sd_uhs2_detect(struct mmc_host *host)
>>                 mmc_claim_host(host);
>>                 mmc_detach_bus(host);
>>                 sd_uhs2_power_off(host);
>> -               host->flags &= ~MMC_UHS2_SUPPORT;
>> +               /* Remove UHS2 timing to indicate the end of UHS2 mode */
>> +               host->ios.timing = MMC_TIMING_LEGACY;
>>                 mmc_release_host(host);
>>         }
>>  }
>> @@ -1338,7 +1340,8 @@ static int sd_uhs2_attach(struct mmc_host *host)
>>  err:
>>         mmc_detach_bus(host);
>>         sd_uhs2_power_off(host);
>> -       host->flags &= ~MMC_UHS2_SUPPORT;
>> +       /* Remove UHS2 timing to indicate the end of UHS2 mode */
>> +       host->ios.timing = MMC_TIMING_LEGACY;
>>         return err;
>>  }
> 
> I wouldn't mind changing to the above. But, maybe an even better
> option is to use the ->timing variable in the struct sdhci_host, as
> it's there already to keep track of the current/previous timing state.
> Would that work too?

The host does not really have enough information.

> 
>>
>> diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
>> index 517c497112f4..d1f3318b7d3a 100644
>> --- a/drivers/mmc/host/sdhci-uhs2.c
>> +++ b/drivers/mmc/host/sdhci-uhs2.c
>> @@ -267,10 +267,11 @@ static void __sdhci_uhs2_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>>
>>         /* UHS2 timing. Note, UHS2 timing is disabled when powering off */
>>         ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>> -       if (ios->timing == MMC_TIMING_UHS2_SPEED_A ||
>> -           ios->timing == MMC_TIMING_UHS2_SPEED_A_HD ||
>> -           ios->timing == MMC_TIMING_UHS2_SPEED_B ||
>> -           ios->timing == MMC_TIMING_UHS2_SPEED_B_HD)
>> +       if (ios->power_mode != MMC_POWER_OFF &&
>> +           (ios->timing == MMC_TIMING_UHS2_SPEED_A ||
>> +            ios->timing == MMC_TIMING_UHS2_SPEED_A_HD ||
>> +            ios->timing == MMC_TIMING_UHS2_SPEED_B ||
>> +            ios->timing == MMC_TIMING_UHS2_SPEED_B_HD))
>>                 ctrl_2 |= SDHCI_CTRL_UHS2 | SDHCI_CTRL_UHS2_ENABLE;
>>         else
>>                 ctrl_2 &= ~(SDHCI_CTRL_UHS2 | SDHCI_CTRL_UHS2_ENABLE);
>>
>>
> 
> Kind regards
> Uffe