Commit a8cd989e authored by Douglas Anderson's avatar Douglas Anderson Committed by Ulf Hansson
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mmc: sdhci-msm: Warn about overclocking SD/MMC 

As talked about in commit 5e4b7e82 ("clk: qcom: gcc-sdm845: Use
floor ops for sdcc clks"), most clocks handled by the Qualcomm clock
drivers are rounded _up_ by default instead of down.  We should make
sure SD/MMC clocks are always rounded down in the clock drivers.
Let's add a warning in the Qualcomm SDHCI driver to help catch the
problem.

This would have saved a bunch of time [1].

NOTE: this doesn't actually fix any problems, it just makes it obvious
to devs that there is a problem and that should be an indication to
fix the clock driver.

[1] http://lore.kernel.org/r/20201210102234.1.I096779f219625148900fc984dd0084ed1ba87c7f@changeid



Suggested-by: default avatarStephen Boyd <swboyd@chromium.org>
Signed-off-by: default avatarDouglas Anderson <dianders@chromium.org>
Reviewed-by: default avatarStephen Boyd <swboyd@chromium.org>
Reviewed-by: default avatarBjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20201214092048.v5.1.Iec3430c7d3c2a29262695edef7b82a14aaa567e5@changeid


Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent 3536b82e

drivers/mmc/host/sdhci-msm.c

+13 −2
Original line number Diff line number Diff line
@@ -352,6 +352,7 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host, 
	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);

	struct mmc_ios curr_ios = host->mmc->ios;

	struct clk *core_clk = msm_host->bulk_clks[0].clk;

	unsigned long achieved_rate;

	int rc;



	clock = msm_get_clock_rate_for_bus_mode(host, clock);
@@ -362,10 +363,20 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host, 
		       curr_ios.timing);

		return;

	}



	/*

	 * Qualcomm clock drivers by default round clock _up_ if they can't

	 * make the requested rate.  This is not good for SD.  Yell if we

	 * encounter it.

	 */

	achieved_rate = clk_get_rate(core_clk);

	if (achieved_rate > clock)

		pr_warn("%s: Card appears overclocked; req %u Hz, actual %lu Hz\n",

			mmc_hostname(host->mmc), clock, achieved_rate);



	msm_host->clk_rate = clock;

	pr_debug("%s: Setting clock at rate %lu at timing %d\n",

		 mmc_hostname(host->mmc), clk_get_rate(core_clk),

		 curr_ios.timing);

		 mmc_hostname(host->mmc), achieved_rate, curr_ios.timing);

}



/* Platform specific tuning */