Re: [RFC PATCH V3 13/21] mmc: sdhci: UHS-II support, skip signal_voltage_switch()

Adrian Hunter
2020-09-14T08:10:27Z

On 14/09/20 9:40 am, AKASHI Takahiro wrote:
> Adrian,
>
> On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote:
>> On 10/07/20 2:11 pm, Ben Chuang wrote:
>>> From: AKASHI Takahiro <takahiro.akashi@linaro.org>
>>>
>>> sdhci_start_signal_voltage_switch() should be called only in UHS-I mode,
>>> and not for UHS-II mode.
>>>
>>> Signed-off-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
>>> ---
>>> drivers/mmc/host/sdhci.c | 7 ++++++-
>>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>> index 5511649946b9..7f2537648a08 100644
>>> --- a/drivers/mmc/host/sdhci.c
>>> +++ b/drivers/mmc/host/sdhci.c
>>> @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
>>> /*
>>> * Signal Voltage Switching is only applicable for Host Controllers
>>> * v3.00 and above.
>>> + * But for UHS2, the signal voltage is supplied by vdd2 which is
>>> + * already 1.8v so no voltage switch required.
>>> */
>>> - if (host->version < SDHCI_SPEC_300)
>>> + if (host->version < SDHCI_SPEC_300 ||
>>> + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
>>> + host->version >= SDHCI_SPEC_400 &&
>>> + host->mmc->flags & MMC_UHS2_SUPPORT))
>>
>> Please look at hooking ->start_signal_voltage_switch() instead
>
> Do you mean that you want every platform driver who wants to support UHS-II
> to set NULL to start_signal_voltage_switch hook even if this hack is
> platform agnostic?

No, I see UHS-II as a separate layer i.e.

UHS-II host controller driver
| |
| v
| sdhci-uhs2 e.g. sdhci_uhs2_start_signal_voltage_switch
| |
v v
sdhci e.g. sdhci_start_signal_voltage_switch

Most things should go through sdhci-uhs2 but not nessarily everything.