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mmc: core: properly select voltage range without power cycle

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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@foss.st.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20221028073740.7259-1-yann.gautier@foss.st.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Yann Gautier 2022-10-28 09:37:40 +02:00 committed by Ulf Hansson
parent 094226ad94
commit 39a72dbfe1
1 changed files with 7 additions and 1 deletions
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8
drivers/mmc/core/core.c
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@ -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");
}