* [PATCH v2] mmc: sdhci-msm: Warn about overclocking SD/MMC
@ 2020-12-10 21:19 Douglas Anderson
2020-12-10 21:23 ` Doug Anderson
0 siblings, 1 reply; 2+ messages in thread
From: Douglas Anderson @ 2020-12-10 21:19 UTC (permalink / raw)
To: Ulf Hansson, Adrian Hunter
Cc: vbadigan, Stephen Boyd, Taniya Das, Douglas Anderson, Andy Gross,
Bjorn Andersson, linux-arm-msm, linux-kernel, linux-mmc
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 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..52824c6b2073 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 %d 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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] mmc: sdhci-msm: Warn about overclocking SD/MMC
2020-12-10 21:19 [PATCH v2] mmc: sdhci-msm: Warn about overclocking SD/MMC Douglas Anderson
@ 2020-12-10 21:23 ` Doug Anderson
0 siblings, 0 replies; 2+ messages in thread
From: Doug Anderson @ 2020-12-10 21:23 UTC (permalink / raw)
To: Ulf Hansson, Adrian Hunter
Cc: Veerabhadrarao Badiganti, Stephen Boyd, Taniya Das, Andy Gross,
Bjorn Andersson, linux-arm-msm, LKML, Linux MMC List
Hi,
On Thu, Dec 10, 2020 at 1:19 PM Douglas Anderson <dianders@chromium.org> wrote:
>
> + pr_warn("%s: Card appears overclocked; req %u Hz, actual %d Hz\n",
> + mmc_hostname(host->mmc), clock, achieved_rate);
Ugh, multitasking too heavily. Clearly this is wrong format codes...
v3 coming shortly. Sorry for the spam.
^ permalink raw reply [flat|nested] 2+ messages in thread
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