linux-kernel - Re: [PATCH V2 1/7] mmc: sdhci: add sd host v4 mode

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Date:   Thu, 21 Jun 2018 19:14:41 +0800
From:   Chunyan Zhang <zhang.lyra@...il.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Chunyan Zhang <zhang.chunyan@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-mmc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...aro.org>,
        Billows Wu <billows.wu@...eadtrum.com>
Subject: Re: [PATCH V2 1/7] mmc: sdhci: add sd host v4 mode

On 21 June 2018 at 18:49, Adrian Hunter <adrian.hunter@...el.com> wrote:
> On 15/06/18 05:04, Chunyan Zhang wrote:
>> For SD host controller version 4.00 or later ones, there're two
>> modes of implementation - Version 3.00 compatible mode or
>> Version 4 mode.  This patch introduces a flag to record this.
>>
>> Signed-off-by: Chunyan Zhang <zhang.chunyan@...aro.org>
>> ---
>>  drivers/mmc/host/sdhci.c | 6 ++++++
>>  drivers/mmc/host/sdhci.h | 6 ++++++
>>  2 files changed, 12 insertions(+)
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index 2ededa7f..cf5695f 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -3302,6 +3302,12 @@ void __sdhci_read_caps(struct sdhci_host *host, u16 *ver, u32 *caps, u32 *caps1)
>>       v = ver ? *ver : sdhci_readw(host, SDHCI_HOST_VERSION);
>>       host->version = (v & SDHCI_SPEC_VER_MASK) >> SDHCI_SPEC_VER_SHIFT;
>>
>> +     if (host->version >= SDHCI_SPEC_400) {
>> +             if (sdhci_readw(host, SDHCI_HOST_CONTROL2) &
>> +                     SDHCI_CTRL_V4_MODE)
>> +                     host->v4_mode = true;
>> +     }
>
> At this point the host controller has just been reset which would mean it
> must be in version 3 compatibility mode, which would mean this code doesn't
> do anything.

Why is it version 3 mode at this point?

I've tested this code on the sd host controller which was introduced
in 6/7 in this patch-set, the result showed that it was v4_mode.
Moreover without this patch, the Spreadtrum's sdhci driver in patch
6/7 couldn't work.

Am I missing something here?

Best,
Chunyan

>
>> +
>>       if (host->quirks & SDHCI_QUIRK_MISSING_CAPS)
>>               return;
>>
>> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
>> index c95b0a4..128b0ba 100644
>> --- a/drivers/mmc/host/sdhci.h
>> +++ b/drivers/mmc/host/sdhci.h
>> @@ -184,6 +184,7 @@
>>  #define   SDHCI_CTRL_DRV_TYPE_D              0x0030
>>  #define  SDHCI_CTRL_EXEC_TUNING              0x0040
>>  #define  SDHCI_CTRL_TUNED_CLK                0x0080
>> +#define  SDHCI_CTRL_V4_MODE          0x1000
>>  #define  SDHCI_CTRL_PRESET_VAL_ENABLE        0x8000
>>
>>  #define SDHCI_CAPABILITIES   0x40
>> @@ -270,6 +271,8 @@
>>  #define   SDHCI_SPEC_100     0
>>  #define   SDHCI_SPEC_200     1
>>  #define   SDHCI_SPEC_300     2
>> +#define   SDHCI_SPEC_400     3
>> +#define   SDHCI_SPEC_410     4
>>
>>  /*
>>   * End of controller registers.
>> @@ -551,6 +554,9 @@ struct sdhci_host {
>>       u32                     sdma_boundary;
>>
>>       unsigned long private[0] ____cacheline_aligned;
>> +
>> +     /* Host Version 4 Enable */
>> +     bool                    v4_mode;
>>  };
>>
>>  struct sdhci_ops {
>>
>