Re: [PATCH v2 6/9] mmc: meson-gx: remove unneeded meson_mmc_clk_set in meson_mmc_clk_init

Heiner Kallweit
2017-02-18T10:49:55Z

Am 18.02.2017 um 11:37 schrieb Heiner Kallweit:
> Am 18.02.2017 um 04:44 schrieb Michał Zegan:
>> Hello Heiner,
>>
>> W dniu 16.02.2017 o 20:42, Heiner Kallweit pisze:
>>> This clk_disable_unprepare isn't right here. At first the condition
>>> should be "if (ret)" as the disable/unprepare is supposed to be
>>> executed if the previous command fails.
>>> And if the previous command fails and meson_mmc_clk_init returns
>>> an error, then probe jumps to label free_host where we have this
>>> disable/unprepare already.
>>>
>>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>>> ---
>>> v2:
>>> - extended commit message
>>> ---
>>> drivers/mmc/host/meson-gx-mmc.c | 6 +-----
>>> 1 file changed, 1 insertion(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
>>> index 68e76fa8..850b0152 100644
>>> --- a/drivers/mmc/host/meson-gx-mmc.c
>>> +++ b/drivers/mmc/host/meson-gx-mmc.c
>>> @@ -320,11 +320,7 @@ static int meson_mmc_clk_init(struct meson_host *host)
>>> /* Get the nearest minimum clock to 400KHz */
>>> host->mmc->f_min = clk_round_rate(host->cfg_div_clk, 400000);
>>>
>>> - ret = meson_mmc_clk_set(host, host->mmc->f_min);
>>> - if (!ret)
>>> - clk_disable_unprepare(host->cfg_div_clk);
>>> -
>>> - return ret;
>>> + return meson_mmc_clk_set(host, host->mmc->f_min);
>>> }
>>>
>>> static void meson_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>>>
>>
>> I see one problem here.
>> As you said, if the previous command (that is the meson_mmc_clk_set
>> function call) fails, then the whole meson_mmc_clk_init returns an error
>> value, and meson_mmc_probe jumps to free_host and disables the clock there.
>> But what happens if the clk_prepare_enable is the line that fails? in
>> this case, the function returns an error value too, and in the free_host
>> meson_mmc_probe tries to disable the clock that is not enabled, and that
>> probably results in a kernel warning because you tried to disable a
>> disabled clock.
>> I was preparing a patch to disable clocks in the probe function only if
>> they were enabled before, but then the meson_mmc_clk_init function
>> remains a problem, because we don't know if the clock was enabled
>> successfully or not when it returns an error.
>>
> Thanks for pointing out, you're right. The solution however should be
> quite easy. I meson_mmc_clk_init we just change the condition of
> the disable/unprepare to "if (ret)" and in probe we remove this
> disable/unprepare from the error path.
>
This was a little too fast, it's not that easy. But I'll come up with
a changed version.