linux-kernel - Re: [PATCH] mmc: core: Fix mmc_select

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Date:	Tue, 7 Jun 2016 14:57:02 +0100
From:	Peter Griffin <peter.griffin@...aro.org>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel@...inux.com, ulf.hansson@...aro.org,
	adrian.hunter@...el.com, linux-mmc@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] mmc: core: Fix mmc_select_hs200() regression in v4.7-rc.

Hi Lee,

On Tue, 07 Jun 2016, Lee Jones wrote:

> On Tue, 07 Jun 2016, Peter Griffin wrote:
> 
> > mmc_select_bus_width() returns bus width (4 or 8) on success or
> > zero if unsupported. If bus width is set successfully we then wish
> > to switch to HS200 mode.
> > 
> > This avoids the following error message in v4.70-rc2
> > 
> > [    2.523674] mmc0: mmc_select_hs200 failed, error 3
> > [    2.528516] mmc0: error 3 whilst initialising MMC card
> > 
> > With this patch card is enumerated correctly
> > 
> > [    2.468065] mmc0: new HS200 MMC card at address 0001
> > [    2.468335] mmcblk0: mmc0:0001 P1XXXX 7.20 GiB
> > [    2.468441] mmcblk0boot0: mmc0:0001 P1XXXX partition 1 2.00 MiB
> > [    2.468552] mmcblk0boot1: mmc0:0001 P1XXXX partition 2 2.00 MiB
> > [    2.468651] mmcblk0rpmb: mmc0:0001 P1XXXX partition 3 128 KiB
> > [    2.469269]  mmcblk0: p1
> > 
> > Fixes: 287980e (remove lots of IS_ERR_VALUE abuses)
> > Signed-off-by: Peter Griffin <peter.griffin@...aro.org>
> > Cc: Arnd Bergmann <arnd@...db.de>
> > ---
> >  drivers/mmc/core/mmc.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> > index c984321..aafb73d 100644
> > --- a/drivers/mmc/core/mmc.c
> > +++ b/drivers/mmc/core/mmc.c
> > @@ -1276,7 +1276,7 @@ static int mmc_select_hs200(struct mmc_card *card)
> >  	 * switch to HS200 mode if bus width is set successfully.
> >  	 */
> >  	err = mmc_select_bus_width(card);
> > -	if (!err) {
> > +	if (err > 0) {
> >  		val = EXT_CSD_TIMING_HS200 |
> >  		      card->drive_strength << EXT_CSD_DRV_STR_SHIFT;
> >  		err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> > @@ -1583,7 +1583,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
> >  	} else if (mmc_card_hs(card)) {
> >  		/* Select the desired bus width optionally */
> >  		err = mmc_select_bus_width(card);
> > -		if (!err) {
> > +		if (err > 0) {
> >  			err = mmc_select_hs_ddr(card);
> >  			if (err)
> >  				goto free_card;
> 
> Looks like this has already been 'fixed' in -rc2.

Ah, it seems I was on -rc1, not -rc2

> 
> Although, this patch does not work for me.
>     mmc: fix mmc mode selection for HS-DDR and higher
>     
>     When IS_ERR_VALUE was removed from the mmc core code, it was replaced
>     with a simple not-zero check. This does not work, as the value checked
>     is the return value for mmc_select_bus_width, which returns the set
>     bit width on success. This made eMMC modes higher than HS-DDR unusable.
>     
>     Fix this by checking for a positive return value instead.
>     
>     Fixes: 287980e49ffc ("remove lots of IS_ERR_VALUE abuses")
>     Cc: Arnd Bergmann <arnd@...db.de>
>     Signed-off-by: Chen-Yu Tsai <wens@...e.org>
>     Acked-by: Hans de Goede <hdegoede@...hat.com>
>     Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
>     Acked-by: Jaehoon Chung <jh80.chung@...sung.com>
>     Reviewed-by: Shawn Lin <shawn.lin@...k-chips.com>
>     Tested-by: Marcel Ziswiler <marcel.ziswiler@...adex.com>
>     Tested-by: Bjorn Andersson <bjorn.andersson@...aro.org>
>     Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> 
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index c984321..5d438ad 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1276,7 +1276,7 @@ static int mmc_select_hs200(struct mmc_card *card)
>  	 * switch to HS200 mode if bus width is set successfully.
>  	 */
>  	err = mmc_select_bus_width(card);
> -	if (!err) {
> +	if (err >= 0) {


This patch looks wrong to me, as if zero is returned by mmc_select_bus_width() it
means setting the bus width failed, and you most likely don't want to switch to
hs200 mode.

Ulf - what is your opinion?

regards,

Peter.>