linux-kernel - Re: [PATCH v1 2/2] mmc: cavium: Remove redundant if-statement checkup

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Message-ID: <CAPDyKFrU591aeH5GyuuQW8tPeNc9wav=t8wqF1EdTBbCc9xheg@mail.gmail.com>
Date:   Fri, 19 Mar 2021 15:09:55 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Bean Huo <huobean@...il.com>
Cc:     rric@...nel.org, Linus Walleij <linus.walleij@...aro.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Bean Huo (beanhuo)" <beanhuo@...ron.com>,
        "# 4.0+" <stable@...r.kernel.org>
Subject: Re: [PATCH v1 2/2] mmc: cavium: Remove redundant if-statement checkup

On Fri, 19 Mar 2021 at 13:14, Bean Huo <huobean@...il.com> wrote:
>
> From: Bean Huo <beanhuo@...ron.com>
>
> Currently, we have two ways to issue multiple-block read/write the
> command to the eMMC. One is by normal IO request path fs->block->mmc.
> Another one is that we can issue multiple-block read/write through
> MMC ioctl interface. For the first path, mrq->stop, and mrq->stop->opcode
> will be initialized in mmc_blk_data_prep(). However, for the second IO
> path, mrq->stop is not initialized since it is a pre-defined multiple
> blocks read/write.

As a matter of fact this way is also supported for the regular block
I/O path. To make the mmc block driver to use it, mmc host drivers
need to announce that it's supported by setting MMC_CAP_CMD23.

It looks like that is what your patch should be targeted towards, can
you have a look at this instead?

Kind regards
Uffe

>
> Meanwhile, if it is open-ended multiple block read/write command,
> STOP_TRANSMISSION CMD12 will be issued later in mmc_blk_issue_drv_op(),
> since it is MMC_IOC_MULTI_CMD.
>
> So, delete these if-statement checkups, let these kinds of multiple-block
> read/write request go.
>
> Fixes 'ba3869ff32e4 ("mmc: cavium: Add core MMC driver for Cavium SOCs")'
> Cc: stable@...r.kernel.org
> Signed-off-by: Bean Huo <beanhuo@...ron.com>
> ---
>  drivers/mmc/host/cavium.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/cavium.c b/drivers/mmc/host/cavium.c
> index 95a41983c6c0..8fb7cbcf62ad 100644
> --- a/drivers/mmc/host/cavium.c
> +++ b/drivers/mmc/host/cavium.c
> @@ -654,8 +654,7 @@ static void cvm_mmc_dma_request(struct mmc_host *mmc,
>         struct mmc_data *data;
>         u64 emm_dma, addr;
>
> -       if (!mrq->data || !mrq->data->sg || !mrq->data->sg_len ||
> -           !mrq->stop || mrq->stop->opcode != MMC_STOP_TRANSMISSION) {
> +       if (!mrq->data || !mrq->data->sg || !mrq->data->sg_len) {
>                 dev_err(&mmc->card->dev, "Error: %s no data\n", __func__);
>                 goto error;
>         }
> --
> 2.25.1
>