linux-kernel - Re: [PATCH V12 12/23] mmc: sdhci-uhs2: skip signal_voltage

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Message-ID: <8c80f712-45c3-4c7a-a694-11efa4591078@intel.com>
Date:   Fri, 6 Oct 2023 13:50:59 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Victor Shih <victorshihgli@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        benchuanggli@...il.com, HL.Liu@...esyslogic.com.tw,
        Greg.tu@...esyslogic.com.tw, takahiro.akashi@...aro.org,
        dlunev@...omium.org, Ben Chuang <ben.chuang@...esyslogic.com.tw>,
        Victor Shih <victor.shih@...esyslogic.com.tw>
Subject: Re: [PATCH V12 12/23] mmc: sdhci-uhs2: skip signal_voltage_switch()

On 6/10/23 13:30, Victor Shih wrote:
> On Tue, Oct 3, 2023 at 5:58 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
>>
>> On Fri, 15 Sept 2023 at 11:44, Victor Shih <victorshihgli@...il.com> wrote:
>>>
>>> From: Victor Shih <victor.shih@...esyslogic.com.tw>
>>>
>>> For UHS2, the signal voltage is supplied by vdd2 which is already 1.8v,
>>> so no voltage switch required.
>>
>> Can you please elaborate on this? I don't get anything of the above, sorry.
>>
>>>
>>> Signed-off-by: Ben Chuang <ben.chuang@...esyslogic.com.tw>
>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
>>> Signed-off-by: Victor Shih <victor.shih@...esyslogic.com.tw>
>>> Acked-by: Adrian Hunter <adrian.hunter@...el.com>
>>> ---
>>>
>>> Updates in V5:
>>>  - Use sdhci_uhs2_mode() to simplify code in
>>>    sdhci_uhs2_start_signal_voltage_switch().
>>>
>>> ---
>>>
>>>  drivers/mmc/host/sdhci-uhs2.c | 24 ++++++++++++++++++++++++
>>>  1 file changed, 24 insertions(+)
>>>
>>> diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
>>> index fc37a34629c2..92fb69b7e209 100644
>>> --- a/drivers/mmc/host/sdhci-uhs2.c
>>> +++ b/drivers/mmc/host/sdhci-uhs2.c
>>> @@ -142,6 +142,27 @@ static void sdhci_uhs2_set_power(struct sdhci_host *host, unsigned char mode, un
>>>         }
>>>  }
>>>
>>> +/*****************************************************************************\
>>> + *                                                                           *
>>> + * MMC callbacks                                                             *
>>> + *                                                                           *
>>> +\*****************************************************************************/
>>> +
>>> +static int sdhci_uhs2_start_signal_voltage_switch(struct mmc_host *mmc,
>>> +                                                 struct mmc_ios *ios)
>>> +{
>>> +       struct sdhci_host *host = mmc_priv(mmc);
>>> +
>>> +       /*
>>> +        * For UHS2, the signal voltage is supplied by vdd2 which is
>>> +        * already 1.8v so no voltage switch required.
>>> +        */
>>> +       if (sdhci_uhs2_mode(host))
>>> +               return 0;
>>
>> This is just wrong. If we are initializing a uhs2 card, we certainly
>> should call ->start_signal_voltage_switch() callback at all. This is
>> for UHS-I cards, right?
>>
> 
> Hi, Ulf
> 
> UHS-II does not need single_voltage.
> I will modify the commit message in the next version.
> sdhci_uhs2_start_signal_voltage_switch() is under
> mmc_host_ops.start_signal_voltage_switch host ops,
> therefore, we need to keep the UHS-I path here.

You should be able to leave out the patch entirely
because ->start_signal_voltage_switch() is not called
for UHS2 mode

> 
> Thanks, Victor Shih
> 
>>> +
>>> +       return sdhci_start_signal_voltage_switch(mmc, ios);
>>> +}
>>> +
>>>  /*****************************************************************************\
>>>   *                                                                           *
>>>   * Driver init/exit                                                          *
>>> @@ -150,6 +171,9 @@ static void sdhci_uhs2_set_power(struct sdhci_host *host, unsigned char mode, un
>>>
>>>  static int sdhci_uhs2_host_ops_init(struct sdhci_host *host)
>>>  {
>>> +       host->mmc_host_ops.start_signal_voltage_switch =
>>> +               sdhci_uhs2_start_signal_voltage_switch;
>>> +
>>>         return 0;
>>>  }
>>>
>>
>> Kind regards
>> Uffe