linux-kernel - Re: [PATCH v2 2/4] mmc: mmci: move block size validation under relevant code

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Date:	Tue, 19 Aug 2014 13:55:37 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:	linux-mmc <linux-mmc@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Chris Ball <chris@...ntf.net>,
	Russell King <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] mmc: mmci: move block size validation under
 relevant code

On 19 August 2014 13:14, Srinivas Kandagatla
<srinivas.kandagatla@...aro.org> wrote:
> This code moves a BUG_ON condition to relevant if block, this check is
> not necessary for IPs which can set any arbitrary block size in a given
> range.
> This patch is necessary for SDIO which sets block sizes that are exactly
> not power of 2.
>
> Original issue detected while testing WLAN ath6kl on Qualcomm APQ8064 SOC.
>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>  drivers/mmc/host/mmci.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> index 3089fba..1c99195 100644
> --- a/drivers/mmc/host/mmci.c
> +++ b/drivers/mmc/host/mmci.c
> @@ -800,15 +800,16 @@ static void mmci_start_data(struct mmci_host *host, struct mmc_data *data)
>         writel(timeout, base + MMCIDATATIMER);
>         writel(host->size, base + MMCIDATALENGTH);
>
> -       blksz_bits = ffs(data->blksz) - 1;
> -       BUG_ON(1 << blksz_bits != data->blksz);

I don't like this BUG_ON at all, I would prefer if we remove it. The
original patch "mmc: mmci: Support any block sizes for ux500v2", did
so as well.

Now, if we still think removing it is fragile, let additional tests in
mmci_validate_data() and return and error code from there.

Kind regards
Uffe

>
> -       if (variant->blksz_datactrl16)
> +       if (variant->blksz_datactrl16) {
>                 datactrl = MCI_DPSM_ENABLE | (data->blksz << 16);
> -       else if (variant->blksz_datactrl4)
> +       } else if (variant->blksz_datactrl4) {
>                 datactrl = MCI_DPSM_ENABLE | (data->blksz << 4);
> -       else
> +       } else {
> +               blksz_bits = ffs(data->blksz) - 1;
> +               BUG_ON(1 << blksz_bits != data->blksz);
>                 datactrl = MCI_DPSM_ENABLE | blksz_bits << 4;
> +       }
>
>         if (data->flags & MMC_DATA_READ)
>                 datactrl |= MCI_DPSM_DIRECTION;
> --
> 1.9.1
>
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