linux-kernel - Re: [PATCH 1/2] mmc: rtsx: add delay before power on

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Message-ID: <CAPDyKFro-dWCOVx=a1BhEJ=J=Hj_+nU+FmTUZjkeAkCqtML=kA@mail.gmail.com>
Date:   Wed, 13 Jan 2021 10:58:32 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     吳昊澄 Ricky <ricky_wu@...ltek.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rui Feng <rui_feng@...lsil.com.cn>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        Doug Anderson <dianders@...omium.org>,
        Lee Jones <lee.jones@...aro.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mmc: rtsx: add delay before power on

On Wed, 30 Dec 2020 at 10:04, <ricky_wu@...ltek.com> wrote:
>
> From: Ricky Wu <ricky_wu@...ltek.com>
>
> Make sure voltage below 0.5V before power on
> when do power cycle
>
> Signed-off-by: Ricky Wu <ricky_wu@...ltek.com>
> ---
>  drivers/mmc/host/rtsx_pci_sdmmc.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/mmc/host/rtsx_pci_sdmmc.c b/drivers/mmc/host/rtsx_pci_sdmmc.c
> index e6f5bbce5685..d21b99962b36 100644
> --- a/drivers/mmc/host/rtsx_pci_sdmmc.c
> +++ b/drivers/mmc/host/rtsx_pci_sdmmc.c
> @@ -906,6 +906,8 @@ static int sd_power_on(struct realtek_pci_sdmmc *host)
>         if (host->power_state == SDMMC_POWER_ON)
>                 return 0;
>
> +       mdelay(100);
> +

Why exactly 100 ms? Can you at least add a comment about why in the code?

Moreover, I think you should convert to use msleep() rather than mdelay.

>         rtsx_pci_init_cmd(pcr);
>         rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, CARD_SELECT, 0x07, SD_MOD_SEL);
>         rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, CARD_SHARE_MODE,
> --
> 2.17.1
>

Kind regards
Uffe