Commit e46bcd42 authored Jan 21, 2014 by Sujit Reddy Thumma

mmc: sdhci: Fix possible spec. violation during voltage switch sequence



With commit 0797e5f1 (mmc: core: Fixup signal voltage switch), voltage
switch sequence for UHS-I cards is broken if used with sdhci driver.
The commit expects the SD clock to be disabled when mmc_set_ios() is
issued but sdhci_do_set_ios() re-enables the SD clock for few cycles
after disabling which is a specification violation during voltage
switch sequence. This failure is observed only for a small group of
cards where they ultimately fall-back into high-speed mode even if
UHS-I modes are supported.

Change-Id: Ie275326627a84bfcd4352637a043296c01c175a6
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>

parent 5f4d31f2

drivers/mmc/host/sdhci.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -1944,6 +1944,7 @@ static void sdhci_do_set_ios(struct sdhci_host host, struct mmc_ios ios)
		sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);

		/* Re-enable SD Clock */
		if (ios->clock)
		flags = sdhci_update_clock(host, flags);
		}

		@@ -1990,6 +1991,7 @@ static void sdhci_do_set_ios(struct sdhci_host host, struct mmc_ios ios)
		}

		/* Re-enable SD Clock */
		if (ios->clock)
		flags = sdhci_update_clock(host, flags);
		} else
		sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);