[Linux-stm32] [PATCH 1/3] mmc: Prepare all code for mmc_set_signal_voltage() returning > 0

[Marek Vasut]

On 4/15/20 10:40 AM, Ulf Hansson wrote:
> On Wed, 1 Apr 2020 at 21:57, Marek Vasut <marex at denx.de> wrote:
>>
>> Patch all drivers and core code which uses mmc_set_signal_voltage()
>> and prepare it for the fact that mmc_set_signal_voltage() can return
>> a value > 0, which would happen if the signal voltage switch did NOT
>> happen, because the voltage was already set correctly.
> 
> I am not sure why you want to change mmc_set_signal_voltage(), can you
> elaborate on that?
> 
> I thought we discussed changing mmc_regulator_set_vqmmc(), what am I missing?

Because mmc_set_signal_voltage() optionally calls
host->ops_>start_signal_voltage_switch() , which can now return value >
0 , so the rest of the core needs to be patched to cater for that.

[...]

>> diff --git a/drivers/mmc/host/dw_mmc-k3.c b/drivers/mmc/host/dw_mmc-k3.c
>> index 23b6f65b3785..50977ff18074 100644
>> --- a/drivers/mmc/host/dw_mmc-k3.c
>> +++ b/drivers/mmc/host/dw_mmc-k3.c
>> @@ -424,7 +424,7 @@ static int dw_mci_hi3660_switch_voltage(struct mmc_host *mmc,
>>
>>         if (!IS_ERR(mmc->supply.vqmmc)) {
>>                 ret = mmc_regulator_set_vqmmc(mmc, ios);
>> -               if (ret) {
>> +               if (ret < 0) {
> 
> This change makes sense to me, however it's also a bit confusing, as
> the changelog refers to changes for mmc_set_signal_voltage().
> 
> As I understand it, we want mmc_regulator_set_vqmmc() to return 1, in
> case the current voltage level is the same as the requested "new"
> target".

Yes. So a failure is now only a return value < 0.

>>                         dev_err(host->dev, "Regulator set error %d\n", ret);
>>                         return ret;
>>                 }
> 
> [...]
> 
> So, to conclude, it seems like $subject patch needs to be reworked a
> bit - just keep the changes you have made to the host drivers, then
> throw away the other parts in core.

I think the core parts are necessary as well though , see above.