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].
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: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
---
Changes in v4:
- Emphasize in the commit message that this itself doesn't fix anything.
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
