linux-kernel - Re: [PATCH 1/3] mmc: core: need do mmc_power_cycle in mmc_sdio_resend_if

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Date:   Fri, 24 Apr 2020 12:09:37 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Yong Mao <yong.mao@...iatek.com>
Cc:     Chaotian Jing <chaotian.jing@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        srv_heupstream <srv_heupstream@...iatek.com>
Subject: Re: [PATCH 1/3] mmc: core: need do mmc_power_cycle in mmc_sdio_resend_if_cond

On Tue, 14 Apr 2020 at 05:40, Yong Mao <yong.mao@...iatek.com> wrote:
>
> From: yong mao <yong.mao@...iatek.com>
>
> When mmc_sdio_resned_if_cond is invoked, it indicates the SDIO
> device is not in the right state. In this condition, the previous
> implementation of mmc_sdio_resend_if_cond can't make sure SDIO
> device be back to idle state. mmc_power_cycle can reset the SDIO
> device by HW and also make sure SDIO device enter to idle state
> correctly.
>
> Signed-off-by: Yong Mao <yong.mao@...iatek.com>
> ---
>  drivers/mmc/core/sdio.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> index ebb387a..ada0a80 100644
> --- a/drivers/mmc/core/sdio.c
> +++ b/drivers/mmc/core/sdio.c
> @@ -546,6 +546,7 @@ static int mmc_sdio_init_uhs_card(struct mmc_card *card)
>  static void mmc_sdio_resend_if_cond(struct mmc_host *host,
>                                     struct mmc_card *card)
>  {
> +       mmc_power_cycle(host, host->card->ocr);

This looks wrong to me. mmc_sdio_resend_if_cond() is called from two places.

1. In the case when mmc_set_uhs_voltage() fails in
mmc_sdio_init_card(), which means a call to mmc_power_cycle() has
already been done.

2. Wen sdio_read_cccr() fails and when we decide to retry the UHS-I
voltage switch. Then perhaps it could make sense to run a power cycle.
But if so, we better do it only for that path.

I will continue to look a bit, as I think there are really more issues
that we may want to look into while looking at this piece of code.
However, allow me some more time before I can provide some more ideas
of how to move forward.

>         sdio_reset(host);
>         mmc_go_idle(host);
>         mmc_send_if_cond(host, host->ocr_avail);
> --
> 1.9.1

Kind regards
Uffe