Re: [PATCH] ath10k: remove mmc_hw_reset while hif power down

From: Kalle Valo <kvalo@codeaurora.org>
To: Wen Gong <wgong@qti.qualcomm.com>
Cc: Grant Grundler <grundler@google.com>,
	Wen Gong <wgong@codeaurora.org>,
	"linux-wireless\@vger.kernel.org"
	<linux-wireless@vger.kernel.org>,
	"ath10k\@lists.infradead.org" <ath10k@lists.infradead.org>,
	Ulf Hansson <ulf.hansson@linaro.org>
Subject: Re: [PATCH] ath10k: remove mmc_hw_reset while hif power down
Date: Tue, 07 May 2019 12:34:59 +0300	[thread overview]
Message-ID: <87pnour4jg.fsf@codeaurora.org> (raw)
In-Reply-To: <36950ff25c0747629e60ccb68819e93a@aptaiexm02f.ap.qualcomm.com> (Wen Gong's message of "Tue, 7 May 2019 05:05:21 +0000")

+ Ulf to give comments from SDIO point of view

Wen Gong <wgong@qti.qualcomm.com> writes:

>> -----Original Message-----
>> From: ath10k <ath10k-bounces@lists.infradead.org> On Behalf Of Grant
>> Grundler
>> Sent: Saturday, May 4, 2019 2:01 AM
>> To: Wen Gong <wgong@codeaurora.org>
>> Cc: linux-wireless@vger.kernel.org; ath10k@lists.infradead.org
>> Subject: [EXT] Re: [PATCH] ath10k: remove mmc_hw_reset while hif power
>> down
>> 
>> [repeating comments I made in the gerrit review for Chrome OS :
>> https://chromium-
>> review.googlesource.com/c/chromiumos/third_party/kernel/+/1585667
>> ]
>> 
>> On Sat, Apr 27, 2019 at 7:17 PM Wen Gong <wgong@codeaurora.org> wrote:
>> >
>> > For sdio 3.0 chip, the clock will drop from 200M Hz to 50M Hz after load
>> > ath10k driver, it is because mmc_hw_reset will reset the sdio's power,
>> > then mmc will consider it as sdio 2.0 and drop the clock.
>> 
>> Wen,
>> 5468e784c0600551ca03263f5255a375c05f88e7 commit message gives
>> reasons
>> for adding the mmc_hw_reset() call. The commit message for removing
>> gives different reason for removal. Both are good but second one is
>> incomplete.
>> 
>> The commit message for removal should ALSO explain why adding this
>> call wasn't necessary in the first place OR move the call to a
>> different code path.
>> 
>> > Remove mmc_hw_reset will avoid the drop of clock.
>> 
>> This commit message makes it clear the original patch introduced a new
>> problem. But the original patch fixed a different problem and that
>> this proposed change seems likely to re-introduce and the commit
>> message should explain why that isn't true (or how the original was
>> fixed differently)
>
> The mmc_hw_reset's effect depends on the hardware layout/configure
> software's behavior, recently it will effect the clock of sdio for the
> platform I used. And it will still work well without mmc_hw_reset for
> the platform I Used currently. If sdio cannot work on other platform,
> I think it can add flag in ath10k_hw_params_list for the platform to
> call the mmc_hw_reset depends on the flag.

I don't see how you can use ath10k_hw_params_list to separate SDIO
controller functionality, I assume that's the real reason for difference
of functionality? Maybe this is a bug on the SDIO controller?

Ulf, what do you think? Any suggestions? Full discussion here:

https://patchwork.kernel.org/patch/10920563/

-- 
Kalle Valo