linux-kernel - Re: [linux-sunxi] [PATCH 2/2] mmc: sunxi: fix new timings mode on A64 EMMC (MMC2) controller

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Message-ID: <4ec3370b8c33eb8a411e9b6ee228a9f7@aosc.io>
Date:   Mon, 07 Aug 2017 14:59:24 +0800
From:   icenowy@...c.io
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>, linux-sunxi@...glegroups.com,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [linux-sunxi] [PATCH 2/2] mmc: sunxi: fix new timings mode on A64
 EMMC (MMC2) controller

在 2017-08-06 10:39，Chen-Yu Tsai 写道：
> On Sat, Aug 05, 2017 at 05:35:55AM +0800, Icenowy Zheng wrote:
>> The configuration struct of A64 EMMC(MMC2) compatible used to
>> have the needs_new_timings variable missing, which lead to NULL
>> pointer dereference now when trying to set up the old timings mode, as
>> the old timings mode doesn't exist at all on A64.
> 
> I'm not familiar with the A64's eMMC controller. The datasheet says
> it does not have the timing switch register. It does not say whether
> it is always in the old or new timing mode. "needs_new_timings"
> probably meant that the switch has to be set.
> 
> This fix doesn't really fix the underlying issue, which is the check
> for clk_delays was incorrectly replaced. sun4i/sun5i is also broken.
> 
> Could you try this patch instead:
> 
> <---
> 
> From 23b841a11294cb6a0cf1e146616b068f60c2ec7d Mon Sep 17 00:00:00 2001
> From: Chen-Yu Tsai <wens@...e.org>
> Date: Sun, 6 Aug 2017 10:24:47 +0800
> Subject: [PATCH] mmc: sunxi: Fix NULL pointer reference on clk_delays
> 
> Some SoCs do not support clk delays for MMC in the clock control unit.
> These include the old controllers in A10/A10s/A13/R8, and the new eMMC
> controller in A64. The config structure for these controllers do not
> specify clk_delays, but the check for this was replaced in commit
> b0600daebf31 ("mmc: sunxi: Support controllers that can use both old
> and new timings").
> 
> This patch adds back the check for clk_delays, and also adds comments
> for both checks in sunxi_mmc_clk_set_phase().
> 
> Fixes: b0600daebf31 ("mmc: sunxi: Support controllers that can use
> 		      both old and new timings")
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>

Successfully tested on A64 (SoPine with baseboard and eMMC module).

> ---
>  drivers/mmc/host/sunxi-mmc.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/mmc/host/sunxi-mmc.c 
> b/drivers/mmc/host/sunxi-mmc.c
> index 3777517982dd..020547e5fa45 100644
> --- a/drivers/mmc/host/sunxi-mmc.c
> +++ b/drivers/mmc/host/sunxi-mmc.c
> @@ -722,9 +722,14 @@ static int sunxi_mmc_clk_set_phase(struct
> sunxi_mmc_host *host,
>  {
>  	int index;
> 
> +	/* No need to set clk controller delays under new timings */
>  	if (host->use_new_timings)
>  		return 0;
> 
> +	/* Some old controllers don't support delays */
> +	if (!host->cfg->clk_delays)
> +		return 0;
> +
>  	/* determine delays */
>  	if (rate <= 400000) {
>  		index = SDXC_CLK_400K;
> --
> 2.13.3
> 
> <---
> 
> Separately we should ask what is the proper set of config flags that
> describes the A64 EMMC controller.
> 
> Regards
> ChenYu
> 
>> 
>> Fix this issue by adding this variable and setting it to true in
>> the configuration struct.
>> 
>> Fixes: 4fb3ce07eafa ("mmc: sunxi: Add EMMC (MMC2) controller 
>> compatible")
>> 
>> Signed-off-by: Icenowy Zheng <icenowy@...c.io>
>> ---
>>  drivers/mmc/host/sunxi-mmc.c | 1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/drivers/mmc/host/sunxi-mmc.c 
>> b/drivers/mmc/host/sunxi-mmc.c
>> index 59aba93beffb..4ad643e37014 100644
>> --- a/drivers/mmc/host/sunxi-mmc.c
>> +++ b/drivers/mmc/host/sunxi-mmc.c
>> @@ -1142,6 +1142,7 @@ static const struct sunxi_mmc_cfg 
>> sun50i_a64_emmc_cfg = {
>>  	.idma_des_size_bits = 13,
>>  	.clk_delays = NULL,
>>  	.can_calibrate = true,
>> +	.needs_new_timings = true,
>>  };
>> 
>>  static const struct of_device_id sunxi_mmc_of_match[] = {
>> --
>> 2.13.0
>> 
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> 
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