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SubjectRe: [PATCH V2 1/7] mmc: sdhci: add sd host v4 mode
On 21 June 2018 at 21:15, Adrian Hunter <adrian.hunter@intel.com> wrote:
> On 21/06/18 14:14, Chunyan Zhang wrote:
>> On 21 June 2018 at 18:49, Adrian Hunter <adrian.hunter@intel.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@linaro.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?
>
> According to the specification, reset clears RW fields to zero.
>
>>
>> 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?
>
> It seems the Spreadtrum controller doesn't clear the "Host Version 4 Enable"
> bit upon software reset for all.
>
> Also this seems the wrong way around. The driver should decide whether or
> not to use V4 mode and then the "Host Version 4 Enable" bit should be set
> accordingly.
>
> V4 has been around so long that we can't just enable all supporting hardware
> without risking the possibility it will break some platform. So I suggest

Ok, understand.

> adding a function sdhci_enable_v4_mode() which is called during probe.

Ok, will do, that is more a safe way.

>
>>
>> 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 {
>>>>
>>>
>>
>

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