linux-kernel - Re: [PATCH 1/3] mmc: fix mmc mode selection for HS-DDR and higher

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Date:	Wed, 01 Jun 2016 11:19:06 +0200
From:	Marcel Ziswiler <marcel@...wiler.com>
To:	Chen-Yu Tsai <wens@...e.org>, Ulf Hansson <ulf.hansson@...aro.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	Hans de Goede <hdegoede@...hat.com>, linux-mmc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>, linux-tegra@...r.kernel.org
Subject: Re: [PATCH 1/3] mmc: fix mmc mode selection for HS-DDR and higher

On Sun, 2016-05-29 at 15:04 +0800, Chen-Yu Tsai wrote:
> 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>

This fixes the following eMMC issue as experienced on Apalis T30 as
well:

[    7.194625] mmc1: mmc_select_hs200 failed, error 3
[    7.201549] mmc1: error 3 whilst initialising MMC card

Tested-by: Marcel Ziswiler <marcel.ziswiler@...adex.com>

> ---
>  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 c984321d1881..aafb73d080ca 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;