linux-kernel - Re: [PATCH v2 2/4] mtd: rawnand: Fix nand_choose_best

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Date:   Fri, 19 Nov 2021 10:08:59 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Herve Codina <herve.codina@...tlin.com>
Cc:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2 2/4] mtd: rawnand: Fix nand_choose_best_timings() on
 unsupported interface

Hi Herve,

herve.codina@...tlin.com wrote on Fri, 19 Nov 2021 08:39:07 +0100:

> When the NV-DDR interface is not supported by the NAND chip,
> the value of onfi->nvddr_timing_modes is 0. In this case,
> the best_mode variable value in nand_choose_best_nvddr_timings()
> is -1. The last for-loop is skipped and the function returns an
> uninitialized value.

Actually is not the first time this uninitialized value triggers bells
but, while I think in the SDR path it is still not needed,in the DDR
patch you are right that something is missing.

> If this returned value is 0, the nand_choose_best_sdr_timings()
> is not executed and no 'best timing' are set. This leads the host
> controller and the NAND chip working at default mode 0 timing
> even if a better timing can be used.
> 
> Fix this uninitialzed returned value.

typo                ^

> 
> nand_choose_best_sdr_timings() is pretty similar to
> nand_choose_best_nvddr_timings(). Even if onfi->sdr_timing_modes
> should never be seen as 0, nand_choose_best_sdr_timings() returned
> value is fixed.

I still don't think it really needed by let's keep so  everyone
(including robots) is happy :)

> 
> Fixes: a9ecc8c814e9 ("mtd: rawnand: Choose the best timings, NV-DDR included")
> Signed-off-by: Herve Codina <herve.codina@...tlin.com>
> ---
> Changes v1 to v2:
> - New patch in v2 series
> 
>  drivers/mtd/nand/raw/nand_base.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> index 5c6b065837ef..a130320de412 100644
> --- a/drivers/mtd/nand/raw/nand_base.c
> +++ b/drivers/mtd/nand/raw/nand_base.c
> @@ -926,7 +926,7 @@ int nand_choose_best_sdr_timings(struct nand_chip *chip,
>  				 struct nand_sdr_timings *spec_timings)
>  {
>  	const struct nand_controller_ops *ops = chip->controller->ops;
> -	int best_mode = 0, mode, ret;
> +	int best_mode = 0, mode, ret = -EOPNOTSUPP;
>  
>  	iface->type = NAND_SDR_IFACE;
>  
> @@ -977,7 +977,7 @@ int nand_choose_best_nvddr_timings(struct nand_chip *chip,
>  				   struct nand_nvddr_timings *spec_timings)
>  {
>  	const struct nand_controller_ops *ops = chip->controller->ops;
> -	int best_mode = 0, mode, ret;
> +	int best_mode = 0, mode, ret = -EOPNOTSUPP;
>  
>  	iface->type = NAND_NVDDR_IFACE;
>  


Thanks,
Miquèl