On Thu 10 Dec 15:27 CST 2020, Douglas Anderson wrote:
> As talked about in commit 5e4b7e82d497 ("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].
>
> [1]
> http://lore.kernel.org/r/20201210102234.1.I096779f219625148900fc984dd0084ed1ba87c7f@changeid
>
> Suggested-by: Stephen Boyd <swb...@chromium.org>
> Signed-off-by: Douglas Anderson <diand...@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.anders...@linaro.org>
Regards,
Bjorn
> ---
>
> Changes in v3:
> - Proper printf format code.
>
> Changes in v2:
> - Store rate in unsigned long, not unsigned int.
> - Reuse the clk_get_rate() in the later print.
>
> drivers/mmc/host/sdhci-msm.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index 3451eb325513..50beb407dbe9 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -353,6 +353,7 @@ 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);
> @@ -363,10 +364,20 @@ 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 */
> --
> 2.29.2.576.ga3fc446d84-goog
>
