In mmc_select_voltage(), if there is no full power cycle, the voltage
range selected at the end of the function will be on a single range
(e.g. 3.3V/3.4V). To keep a range around the selected voltage (3.2V/3.4V),
the mask shift should be reduced by 1.
This issue was triggered by using a specific SD-card (Verbatim Premium
16GB UHS-1) on an STM32MP157C-DK2 board. This board cannot do UHS modes
and there is no power cycle. And the card was failing to switch to
high-speed mode. When adding the range 3.2V/3.3V for this card with the
proposed shift change, the card can switch to high-speed mode.
Fixes: ce69d37b7d8f ("mmc: core: Prevent violation of specs while initializing cards")
Signed-off-by: Yann Gautier <yann.gautier@xxxxxxxxxxx>
---
drivers/mmc/core/core.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 95fa8fb1d45f..c5de202f530a 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1134,7 +1134,13 @@ u32 mmc_select_voltage(struct mmc_host *host, u32 ocr)
mmc_power_cycle(host, ocr);
} else {
bit = fls(ocr) - 1;
- ocr &= 3 << bit;
+ /*
+ * The bit variable represents the highest voltage bit set in
+ * the OCR register.
+ * To keep a range of 2 values (e.g. 3.2V/3.3V and 3.3V/3.4V),
+ * we must shift the mask '3' with (bit - 1).
+ */
+ ocr &= 3 << (bit - 1);
if (bit != host->ios.vdd)
dev_warn(mmc_dev(host), "exceeding card's volts\n");
}
--
2.25.1
