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

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Date:   Mon, 4 Feb 2019 10:34:27 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>, linux-mmc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com,
        Chris Blake <chrisrblake93@...il.com>, stable@...r.kernel.org
Subject: Re: [PATCH 2/3] mmc: sunxi: Filter out unsupported modes declared in
 the device tree

On Sun, Feb 03, 2019 at 11:56:27PM +0800, Chen-Yu Tsai 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>
> 
> ---
> 
> 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 | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
> index 7415af8c8ff6..a01433012db0 100644
> --- a/drivers/mmc/host/sunxi-mmc.c
> +++ b/drivers/mmc/host/sunxi-mmc.c
> @@ -1415,6 +1415,22 @@ 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 DDR 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);
> +
> +	/* TODO: UHS modes untested due to lack of supporting boards */
> +	mmc->caps &= ~MMC_CAP_UHS;

I've tested up to SDR104 and it works on the A64 at least

> +	/* TODO: This driver doesn't support HS200 and HS400 modes yet */
> +	mmc->caps2 &= ~(MMC_CAP2_HS200 | MMC_CAP2_HS400);

And HS200 works too.

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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