linux-kernel - Re: [PATCH v2] mmc: renesas_sdhi: Set the SDBUF after reset

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Date: Fri, 26 Apr 2024 07:08:10 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: wsa+renesas@...g-engineering.com
Cc: Claudiu Beznea <claudiu.beznea@...on.dev>, linux-mmc@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>, Hien Huynh <hien.huynh.px@...esas.com>
Subject: Re: [PATCH v2] mmc: renesas_sdhi: Set the SDBUF after reset

On Wed, 10 Apr 2024 at 15:54, Claudiu Beznea <claudiu.beznea@...on.dev> wrote:
>
> For development purpose, renesas_sdhi_probe() could be called w/
> dma_ops = NULL to force the usage of PIO mode. In this case the
> renesas_sdhi_enable_dma() will not be called before transferring data.
>
> If renesas_sdhi_enable_dma() is not called, renesas_sdhi_clk_enable()
> call from renesas_sdhi_probe() will configure SDBUF by calling the
> renesas_sdhi_sdbuf_width() function, but then SDBUF will be reset in
> tmio_mmc_host_probe() when calling tmio_mmc_reset() though host->reset().
> If SDBUF is zero the data transfer will not work in PIO mode for RZ/G3S.
>
> To fix this call again the renesas_sdhi_sdbuf_width(host, 16) in
> renesas_sdhi_reset(). The call of renesas_sdhi_sdbuf_width() was not
> removed from renesas_sdhi_clk_enable() as the host->reset() is optional.
>
> Co-developed-by: Hien Huynh <hien.huynh.px@...esas.com>
> Signed-off-by: Hien Huynh <hien.huynh.px@...esas.com>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

Wolfram, when you have the time, can we get your opinion on this one?

Kind regards
Uffe

> ---
>
> Changes in v2:
> - fixed typos in commit description
> - limit the comment lines to 80 chars
>
>  drivers/mmc/host/renesas_sdhi_core.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/mmc/host/renesas_sdhi_core.c b/drivers/mmc/host/renesas_sdhi_core.c
> index f84f60139bcf..5233731a94c4 100644
> --- a/drivers/mmc/host/renesas_sdhi_core.c
> +++ b/drivers/mmc/host/renesas_sdhi_core.c
> @@ -589,6 +589,12 @@ static void renesas_sdhi_reset(struct tmio_mmc_host *host, bool preserve)
>                         sd_ctrl_write16(host, CTL_RESET_SD, 0x0001);
>                         priv->needs_adjust_hs400 = false;
>                         renesas_sdhi_set_clock(host, host->clk_cache);
> +
> +                       /*
> +                        * In case the controller works in PIO mode the SDBUF
> +                        * needs to be set as its reset value is zero.
> +                        */
> +                       renesas_sdhi_sdbuf_width(host, 16);
>                 } else if (priv->scc_ctl) {
>                         renesas_sdhi_scc_reset(host, priv);
>                 }
> --
> 2.39.2
>