linux-kernel - Re: [PATCH v4 1/5] mmc: sdhci: fix base clock usage in preset value

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Message-ID: <84dfa2fd-0b02-82b3-80ba-f0a9d59d89b6@intel.com>
Date:   Wed, 4 Aug 2021 13:50:15 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Kevin Liu <kliu5@...vell.com>,
        Michal Simek <michal.simek@...inx.com>,
        Suneel Garapati <suneel.garapati@...inx.com>
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Al Cooper <alcooperx@...il.com>
Subject: Re: [PATCH v4 1/5] mmc: sdhci: fix base clock usage in preset value

On 25/07/21 12:20 pm, Michał Mirosław wrote:
> Fixed commit added an unnecessary read of CLOCK_CONTROL. The value read
> is overwritten for programmable clock preset, but is carried over for
> divided clock preset. This can confuse sdhci_enable_clk() if the register
> has enable bits set for some reason at time time of clock calculation.

"time time" -> "time"

> Remove the read.
> 
> Quoting Al Cooper:
> 
> sdhci_brcmstb_set_clock() assumed that sdhci_calc_clk() would always
> return the divider value without the enable set, so this fixes a case
> for DDR52 where the enable was not being cleared when the divider
> value was changed.
> 
> Cc: stable@...r.kernel.org
> Fixes: 52983382c74f ("mmc: sdhci: enhance preset value function")
> Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> Acked-by: Al Cooper <alcooperx@...il.com>

Apart from above:

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> 
> ---
> v4: no changes
> v3: updated commit message
> v2: removed truncated sentence from commitmsg
> 
> Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> ---
>  drivers/mmc/host/sdhci.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index aba6e10b8605..c7438dd13e3e 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1857,7 +1857,6 @@ u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
>  		if (host->preset_enabled) {
>  			u16 pre_val;
>  
> -			clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
>  			pre_val = sdhci_get_preset_value(host);
>  			div = FIELD_GET(SDHCI_PRESET_SDCLK_FREQ_MASK, pre_val);
>  			if (host->clk_mul &&
>