linux-kernel - Re: [PATCH v2 2/3] mmc: sunxi: Filter out unsupported modes declared in the device tree

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Date:   Wed, 6 Feb 2019 16:14:33 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        Chris Blake <chrisrblake93@...il.com>,
        "# 4.0+" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] mmc: sunxi: Filter out unsupported modes declared
 in the device tree

On Tue, 5 Feb 2019 at 16:42, Chen-Yu Tsai <wens@...e.org> wrote:
>
> The MMC device tree bindings include properties used to signal various
> signalling speed modes. Until now the sunxi driver was accepting them
> without any further filtering, while the sunxi device trees were not
> actually using them.
>
> Since some of the H5 boards can not run at higher speed modes stably,
> we are resorting to declaring the higher speed modes per-board.
>
> Regardless, having boards declare modes and blindly following them,
> even without proper support in the driver, is generally a bad thing.
>
> Filter out all unsupported modes from the capabilities mask after
> the device tree properties have been parsed.
>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
>

Applied for fixes, thanks!

Kind regards
Uffe


> ---
>
> This should be backported to stable kernels in case people try to run
> new device trees (that declare newly supported modes) with old kernels.
> ---
>  drivers/mmc/host/sunxi-mmc.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
> index 7415af8c8ff6..70fadc976795 100644
> --- a/drivers/mmc/host/sunxi-mmc.c
> +++ b/drivers/mmc/host/sunxi-mmc.c
> @@ -1415,6 +1415,21 @@ static int sunxi_mmc_probe(struct platform_device *pdev)
>         if (ret)
>                 goto error_free_dma;
>
> +       /*
> +        * If we don't support delay chains in the SoC, we can't use any
> +        * of the higher speed modes. Mask them out in case the device
> +        * tree specifies the properties for them, which gets added to
> +        * the caps by mmc_of_parse() above.
> +        */
> +       if (!(host->cfg->clk_delays || host->use_new_timings)) {
> +               mmc->caps &= ~(MMC_CAP_3_3V_DDR | MMC_CAP_1_8V_DDR |
> +                              MMC_CAP_1_2V_DDR | MMC_CAP_UHS);
> +               mmc->caps2 &= ~MMC_CAP2_HS200;
> +       }
> +
> +       /* TODO: This driver doesn't support HS400 mode yet */
> +       mmc->caps2 &= ~MMC_CAP2_HS400;
> +
>         ret = sunxi_mmc_init_host(host);
>         if (ret)
>                 goto error_free_dma;
> --
> 2.20.1
>