linux-kernel - Re: [<PATCH v1> 1/9] mmc: core: Add a cap to use long discard size

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Date:   Tue, 17 Dec 2019 08:09:32 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     "Bao D. Nguyen" <nguyenb@...eaurora.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Asutosh Das <asutoshd@...eaurora.org>, cang@...eaurora.org
Subject: Re: [<PATCH v1> 1/9] mmc: core: Add a cap to use long discard size

On Tue, 17 Dec 2019 at 03:52, Bao D. Nguyen <nguyenb@...eaurora.org> wrote:
>
> Add MMC_CAP2_MAX_DISCARD_SIZE cap which allows setting the max
> discard size value if needed.
> Setting a high value for the max discard size is to fix an issue where
> some SD cards take a long time to perform the card format.

Can you please explain elaborate on why the SD card takes a long time
to "format"? What goes on and what takes time, etc.

In any case, it looks wrong to add a host cap to solve this problem.

Kind regards
Uffe


>
> Signed-off-by: Bao D. Nguyen <nguyenb@...eaurora.org>
> ---
>  include/linux/mmc/host.h | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index ba70338..f1a767d 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -348,6 +348,7 @@ struct mmc_host {
>  #define MMC_CAP2_FULL_PWR_CYCLE        (1 << 2)        /* Can do full power cycle */
>  #define MMC_CAP2_HS200_1_8V_SDR        (1 << 5)        /* can support */
>  #define MMC_CAP2_HS200_1_2V_SDR        (1 << 6)        /* can support */
> +#define MMC_CAP2_MAX_DISCARD_SIZE (1 << 8)      /* use max discard, ignoring max_busy_timeout parameter */
>  #define MMC_CAP2_HS200         (MMC_CAP2_HS200_1_8V_SDR | \
>                                  MMC_CAP2_HS200_1_2V_SDR)
>  #define MMC_CAP2_CD_ACTIVE_HIGH        (1 << 10)       /* Card-detect signal active high */
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project