diff mbox series

[v3] mmc: sdhci-msm: Warn about overclocking SD/MMC

Message ID 20201210132745.v3.1.Iec3430c7d3c2a29262695edef7b82a14aaa567e5@changeid (mailing list archive)
State New
Headers show
Series [v3] mmc: sdhci-msm: Warn about overclocking SD/MMC | expand

Commit Message

Douglas Anderson Dec. 10, 2020, 9:27 p.m. UTC
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 <swboyd@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

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(-)

Comments

Stephen Boyd Dec. 10, 2020, 9:57 p.m. UTC | #1
Quoting Douglas Anderson (2020-12-10 13:27:52)
> 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 <swboyd@chromium.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Bjorn Andersson Dec. 10, 2020, 10:23 p.m. UTC | #2
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 <swboyd@chromium.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Reviewed-by: Bjorn Andersson <bjorn.andersson@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
>
Adrian Hunter Dec. 11, 2020, 5:56 a.m. UTC | #3
On 10/12/20 11:27 pm, 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 <swboyd@chromium.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
> 
> 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);

How does a warning help?

Also, did you consider setting host->mmc->actual_clock

> +
>  	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 */
>
Douglas Anderson Dec. 11, 2020, 5:15 p.m. UTC | #4
Hi,

On Thu, Dec 10, 2020 at 9:56 PM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> On 10/12/20 11:27 pm, 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 <swboyd@chromium.org>
> > Signed-off-by: Douglas Anderson <dianders@chromium.org>
> > ---
> >
> > 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);
>
> How does a warning help?

The actual fixes are made in the clock drivers, but this seems to be a
common problem in Qualcomm clock drivers.  ...so while this doesn't
actually fix the problem, it hopefully calls enough attention that
someone will know to fix it in the clock driver.


> Also, did you consider setting host->mmc->actual_clock

That makes sense, though I think logically it's a separate change.
I'll add it as patch #2 in the series.  It's not as trivial as I would
have thought.  ;-)

-Doug

>
> > +
> >       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 */
> >
>
diff mbox series

Patch

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 */