[PATCH 3.16 200/245] mmc: sdhci: fix minimum clock rate for v3 controller

Ben Hutchings
2020-04-23T23:11:12Z

From: Michał Mirosław <mirq-linux@rere.qmqm.pl>

commit 2a187d03352086e300daa2044051db00044cd171 upstream.

For SDHCIv3+ with programmable clock mode, minimal clock frequency is
still base clock / max(divider). Minimal programmable clock frequency is
always greater than minimal divided clock frequency. Without this patch,
SDHCI uses out-of-spec initial frequency when multiplier is big enough:

mmc1: mmc_rescan_try_freq: trying to init card at 468750 Hz
[for 480 MHz source clock divided by 1024]

The code in sdhci_calc_clk() already chooses a correct SDCLK clock mode.

Fixes: c3ed3877625f ("mmc: sdhci: add support for programmable clock mode")
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/ffb489519a446caffe7a0a05c4b9372bd52397bb.1579082031.git.mirq-linux@rere.qmqm.pl
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/mmc/host/sdhci.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2945,11 +2945,13 @@ int sdhci_add_host(struct sdhci_host *ho
if (host->ops->get_min_clock)
mmc->f_min = host->ops->get_min_clock(host);
else if (host->version >= SDHCI_SPEC_300) {
- if (host->clk_mul) {
- mmc->f_min = (host->max_clk * host->clk_mul) / 1024;
+ if (host->clk_mul)
mmc->f_max = host->max_clk * host->clk_mul;
- } else
- mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_300;
+ /*
+ * Divided Clock Mode minimum clock rate is always less than
+ * Programmable Clock Mode minimum clock rate.
+ */
+ mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_300;
} else
mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_200;