linux-kernel - Re: [PATCH 1/2] Revert "clk: rockchip: reset init state before mmc card initialization"

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Message-ID: <78aecdae-7b9b-d687-a8d3-44f476ddd73e@rock-chips.com>
Date:	Fri, 13 May 2016 08:19:54 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Douglas Anderson <dianders@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>, mturquette@...libre.com,
	sboyd@...eaurora.org
Cc:	shawn.lin@...k-chips.com, linux-rockchip@...ts.infradead.org,
	zhengxing@...k-chips.com, linux-clk@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] Revert "clk: rockchip: reset init state before mmc
 card initialization"

On 2016/5/13 2:03, Douglas Anderson wrote:
> This reverts commit 7a03fe6f48f3 ("clk: rockchip: reset init state
> before mmc card initialization").
>
> Though not totally obvious from the commit message nor from the source
> code, that commit appears to be trying to reset the "_drv" MMC clocks to
> 90 degrees (note that the "_sample" MMC clocks have a shift of 0 so are
> not touched).

Hrrr...my fault, anyway it should be reverted in case of new register
layout in the future.

Have you found the difference of sample shift between rk3399 and former
Socs?  Per Mobile Storage Host Controller section, it migrate from
bit[1:0] to bit[2:1]...

Acutally there are three register layouts about sdmmc/sdio tuning
stuff I found. Although just two types were upstreamed, it still
caused difficulty. With your patch for dw_mmc to explictly assign
dr_phase, we keep the phase policy better to be unstood and traced.

Again sorry for commit 7a03fe6f48!

>
> The major problem here is that it doesn't properly reset things.  The
> phase is a two bit field and the commit only touches one of the two
> bits.  Thus the commit had the following affect:
> - phase   0  => phase  90
> - phase  90  => phase  90
> - phase 180  => phase 270
> - phase 270  => phase 270
>
> Things get even weirder if you happen to have a bootloader that was
> actually using delay elements (should be no reason to, but you never
> know), since those are additional bits that weren't touched by the
> original patch.
>
> This is unlikely to be what we actually want.  Checking on rk3288-veyron
> devices, I can see that the bootloader leaves these clocks as:
> - emmc:  phase 180
> - sdmmc: phase 90
> - sdio0: phase 90
>
> Thus on rk3288-veyron devices the commit we're reverting had the effect
> of changing the eMMC clock to phase 270.  This probably explains the
> scattered reports I've heard of eMMC devices not working on some veyron
> devices when using the upstream kernel.
>
> The original commit was presumably made because previously the kernel
> didn't touch the "_drv" phase at all and relied on whatever value was
> there when the kernel started.  If someone was using a bootloader that
> touched the "_drv" phase then, indeed, we should have code in the kernel
> to fix that.  ...and also, to get ideal timings, we should also have the
> kernel change the phase depending on the speed mode.  In fact, that's
> the subject of a recent patch I posted at
> <https://patchwork.kernel.org/patch/9075141/>.
>
> Ideally, we should take both the patch posted to dw_mmc and this
> revert.  Since those will likely go through different trees, here I
> describe behavior with the combos:
>
> 1. Just this revert: likely will fix rk3288-veyron eMMC on some devices
>    + other cases; might break someone with a strange bootloader that
>    sets the phase to 0 or one that uses delay elements (pretty
>    unpredicable what would happen in that case).
> 2. Just dw_mmc patch: fixes everyone.  Effectly the dw_mmc patch will
>    totally override the broken patch and fix everything.
> 3. Both patches: fixes everyone.  Once dw_mmc is initting properly then
>    any defaults from the clock code doesn't mattery.
>
> Fixes: 7a03fe6f48f3 ("clk: rockchip: reset init state before mmc card initialization")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>  drivers/clk/rockchip/clk-mmc-phase.c | 11 -----------
>  1 file changed, 11 deletions(-)
>
> diff --git a/drivers/clk/rockchip/clk-mmc-phase.c b/drivers/clk/rockchip/clk-mmc-phase.c
> index bc856f21f6b2..5b18265c2306 100644
> --- a/drivers/clk/rockchip/clk-mmc-phase.c
> +++ b/drivers/clk/rockchip/clk-mmc-phase.c
> @@ -41,8 +41,6 @@ static unsigned long rockchip_mmc_recalc(struct clk_hw *hw,
>  #define ROCKCHIP_MMC_DEGREE_MASK 0x3
>  #define ROCKCHIP_MMC_DELAYNUM_OFFSET 2
>  #define ROCKCHIP_MMC_DELAYNUM_MASK (0xff << ROCKCHIP_MMC_DELAYNUM_OFFSET)
> -#define ROCKCHIP_MMC_INIT_STATE_RESET 0x1
> -#define ROCKCHIP_MMC_INIT_STATE_SHIFT 1
>
>  #define PSECS_PER_SEC 1000000000000LL
>
> @@ -162,15 +160,6 @@ struct clk *rockchip_clk_register_mmc(const char *name,
>  	mmc_clock->reg = reg;
>  	mmc_clock->shift = shift;
>
> -	/*
> -	 * Assert init_state to soft reset the CLKGEN
> -	 * for mmc tuning phase and degree
> -	 */
> -	if (mmc_clock->shift == ROCKCHIP_MMC_INIT_STATE_SHIFT)
> -		writel(HIWORD_UPDATE(ROCKCHIP_MMC_INIT_STATE_RESET,
> -				     ROCKCHIP_MMC_INIT_STATE_RESET,
> -				     mmc_clock->shift), mmc_clock->reg);
> -
>  	clk = clk_register(NULL, &mmc_clock->hw);
>  	if (IS_ERR(clk))
>  		kfree(mmc_clock);
>


-- 
Best Regards
Shawn Lin