linux-kernel - RE: [PATCH V2 1/2] mmc: block: Support Host to control FUA

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Date:   Fri, 21 Oct 2022 07:53:40 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Wenchao Chen <wenchao.chen666@...il.com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
        "orsonzhai@...il.com" <orsonzhai@...il.com>,
        "baolin.wang@...ux.alibaba.com" <baolin.wang@...ux.alibaba.com>,
        "zhang.lyra@...il.com" <zhang.lyra@...il.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "kch@...dia.com" <kch@...dia.com>
CC:     "CLoehle@...erstone.com" <CLoehle@...erstone.com>,
        "vincent.whitchurch@...s.com" <vincent.whitchurch@...s.com>,
        "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
        "s.shtylyov@....ru" <s.shtylyov@....ru>,
        "michael@...winnertech.com" <michael@...winnertech.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "megoo.tang@...il.com" <megoo.tang@...il.com>,
        "lzx.stg@...il.com" <lzx.stg@...il.com>
Subject: RE: [PATCH V2 1/2] mmc: block: Support Host to control FUA

> From: Wenchao Chen <wenchao.chen@...soc.com>
> 
> This patch introduces host->fua_disable for MMC host controller.
> The host can turn off FUA to improve performance.
> 
> Signed-off-by: Wenchao Chen <wenchao.chen@...soc.com>
> ---
> V1 -> V2
> Address Chaitanyak's suggestions
> Address Avri's suggestions
> ---
>  drivers/mmc/core/block.c | 3 ++-
>  include/linux/mmc/host.h | 3 +++
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c index
> 54cd009aee50..333e819e077a 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -2490,7 +2490,8 @@ static struct mmc_blk_data
> *mmc_blk_alloc_req(struct mmc_card *card,
>             ((card->ext_csd.rel_param & EXT_CSD_WR_REL_PARAM_EN) ||
>              card->ext_csd.rel_sectors)) {
>                 md->flags |= MMC_BLK_REL_WR;
> -               fua_enabled = true;
> +               if (!card->host->fua_disable)
> +                       fua_enabled = true;
>                 cache_enabled = true;
>         }
>         if (mmc_cache_enabled(card->host)) diff --git a/include/linux/mmc/host.h
> b/include/linux/mmc/host.h index 8fdd3cf971a3..16a5bee3eeae 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -517,6 +517,9 @@ struct mmc_host {
>         struct blk_crypto_profile crypto_profile;  #endif
> 
> +       /* Host FUA support */
> +       bool                    fua_disable;
Why do you need to invent a LLD mechanism, when you already have a block api (QUEUE_FLAG_FUA) for that?
Which is actually misleading, since /sys/block/mmcblk0/queue/fua will still reads 0.

Thanks,
Avri 

> +
>         /* Host Software Queue support */
>         bool                    hsq_enabled;
> 
> --
> 2.17.1