Re: [PATCH master 1/3] mci: core: fix fallback when eMMC DDR52 is not possible

[Sascha Hauer <s.hauer@pengutronix.de>]

On Tue, Apr 23, 2024 at 08:22:04AM +0200, Ahmad Fatoum wrote:
> mci_mmc_select_hs_ddr() will try DDR52 and if that fails, revert to
> SDR operation. In that case, it returns the bus width, which would
> be forwarded as if it were an error code:
> 
>   WARNING: mmc2: Card's startup fails with 3
> 
> Fix this by translating successful return values to 0 in
> mci_startup_mmc().
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  drivers/mci/mci-core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
> index 1d383e6449e9..57b4c5b99c9c 100644
> --- a/drivers/mci/mci-core.c
> +++ b/drivers/mci/mci-core.c
> @@ -1566,7 +1566,7 @@ static int mci_startup_mmc(struct mci *mci)
>  		}
>  	}
>  
> -	return ret;
> +	return ret >= MMC_BUS_WIDTH_1 ? 0 : ret;
>  }

Can we do it like below instead? It makes clear where a MMC_BUS_WIDTH_x
return value is expected.

Sascha


----------------------------------8<---------------------------

diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
index 083d2f4ed1..da892a5f84 100644
--- a/drivers/mci/mci-core.c
+++ b/drivers/mci/mci-core.c
@@ -1558,8 +1558,12 @@ static int mci_startup_mmc(struct mci *mci)
 
 		/* find out maximum bus width and then try DDR if supported */
 		ret = mci_mmc_select_bus_width(mci);
-		if (ret > MMC_BUS_WIDTH_1 && mci->tran_speed == 52000000)
-			ret = mci_mmc_select_hs_ddr(mci);
+		if (ret > MMC_BUS_WIDTH_1) {
+			ret = 0;
+
+			if (mci->tran_speed == 52000000)
+				ret = mci_mmc_select_hs_ddr(mci);
+		}
 
 		if (ret < 0) {
 			dev_warn(&mci->dev, "Changing MMC bus width failed: %d\n", ret);


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