linux-kernel - Re: [PATCH 2/7] mmc: sdhci: fix programmable clock config from preset value

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Date:   Wed, 15 Apr 2020 15:44:20 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Kevin Liu <kliu5@...vell.com>,
        Michal Simek <michal.simek@...inx.com>,
        Suneel Garapati <suneel.garapati@...inx.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org
Subject: Re: [PATCH 2/7] mmc: sdhci: fix programmable clock config from preset
 value

On 2/04/20 2:54 pm, Michał Mirosław wrote:
> When host controller uses programmable clock presets but doesn't
> advertise programmable clock support, we can only guess what frequency
> it generates. Let's at least return correct SDHCI_PROG_CLOCK_MODE bit
> value in this case.

It sounds like the hardware is broken, so I tend to think a workaround
should be in the relevant vendor driver, because that is where
device-specific information really belongs.

> 
> Fixes: 52983382c74f ("mmc: sdhci: enhance preset value function")
> Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> ---
>  drivers/mmc/host/sdhci.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 9aa3af5826df..b2dc4f1cfa5c 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1767,11 +1767,10 @@ u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
>  
>  			pre_val = sdhci_get_preset_value(host);
>  			div = FIELD_GET(SDHCI_PRESET_SDCLK_FREQ_MASK, pre_val);
> -			if (host->clk_mul &&
> -				(pre_val & SDHCI_PRESET_CLKGEN_SEL)) {
> +			if (pre_val & SDHCI_PRESET_CLKGEN_SEL) {
>  				clk = SDHCI_PROG_CLOCK_MODE;
>  				real_div = div + 1;
> -				clk_mul = host->clk_mul;
> +				clk_mul = host->clk_mul ?: 1;
>  			} else {
>  				real_div = max_t(int, 1, div << 1);
>  			}
>