Re: [PATCH 1/3] mmc: core: need do mmc_power_cycle in mmc_sdio_resend_if_cond

From: "yong.mao@mediatek.com" <yong.mao@mediatek.com>
To: Matthias Kaehlcke <mka@chromium.org>,
	Ulf Hansson <ulf.hansson@linaro.org>
Cc: srv_heupstream@mediatek.com, linux-mmc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
	Chaotian Jing <chaotian.jing@mediatek.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/3] mmc: core: need do mmc_power_cycle in mmc_sdio_resend_if_cond
Date: Tue, 21 Apr 2020 15:03:29 +0800	[thread overview]
Message-ID: <1587452609.19579.14.camel@mhfsdcap03> (raw)
In-Reply-To: <20200420191518.GG199755@google.com>

On Mon, 2020-04-20 at 12:15 -0700, Matthias Kaehlcke wrote:
> Hi,
> 
> On Tue, Apr 14, 2020 at 11:40:09AM +0800, Yong Mao wrote:
> > From: yong mao <yong.mao@mediatek.com>
> > 
> > When mmc_sdio_resned_if_cond is invoked, it indicates the SDIO
> > device is not in the right state. In this condition, the previous
> > implementation of mmc_sdio_resend_if_cond can't make sure SDIO
> > device be back to idle state. mmc_power_cycle can reset the SDIO
> > device by HW and also make sure SDIO device enter to idle state
> > correctly.
> > 
> > Signed-off-by: Yong Mao <yong.mao@mediatek.com>
> > ---
> >  drivers/mmc/core/sdio.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> > index ebb387a..ada0a80 100644
> > --- a/drivers/mmc/core/sdio.c
> > +++ b/drivers/mmc/core/sdio.c
> > @@ -546,6 +546,7 @@ static int mmc_sdio_init_uhs_card(struct mmc_card *card)
> >  static void mmc_sdio_resend_if_cond(struct mmc_host *host,
> >  				    struct mmc_card *card)
> >  {
> > +	mmc_power_cycle(host, host->card->ocr);
> 
> My MMC/SDIO background is limited, but it seems this isn't needed for the
> vast majority of SDIO devices, otherwise it probably would have been added
> earlier. I wonder if it would make sense to make the power cycle
> conditional through a quirk, to limit it to the devices that need it.
> 

Thanks for your comment.
mmc_sdio_resend_if_cond API is not for normal initialization flow, but
for error handle flow. If mmc_sdio_resend_if_cond is invoked, it
indicates there is something wrong with the SDIO device. HW power cycle
is the basic guarantee for device to back to idle state.
Therefore this patch will not affect the normal initialization for the 
vast majority of SDIO devices, but it is very helpful for error cases
for all SDIO devices.
In my opinion, we don't need that quirk.
Could Ulf help to give some advises on this?
Thanks.

> >  	sdio_reset(host);
> >  	mmc_go_idle(host);
> >  	mmc_send_if_cond(host, host->ocr_avail);
> > -- 
> > 1.9.1

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