From ceae98f20e36ffcf579fd5ae74c8f24b00c0f383 Mon Sep 17 00:00:00 2001 From: Tim Kryger Date: Thu, 24 Apr 2014 14:44:26 -0700 Subject: [PATCH] mmc: core: Try other signal levels during power up The eMMC signalling voltage is determined by VCCQ which is provided to the card by the host. Signalling is not required to begin at 3.3v and, if the host and card both support a particular VCC/VCCQ combination, it can be used immediately. In contrast, SD Cards must begin with 3.3v signalling and may switch to a lower voltage signalling if instructed to do so in CMD11. A message is required to coordinate this operation because the card only receives a 3.3v VDD and must know when to use the 1.8v produced by its internal regulator. It makes sense for the core to begin with 3.3v signalling but when that can't be set, 1.8v and 1.2v signalling also should be attempted. This is especially important when an external regulator with a limited range is used to supply VCCQ to an eMMC part. Signed-off-by: Tim Kryger Signed-off-by: Ulf Hansson Signed-off-by: Chris Ball --- drivers/mmc/core/core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index 79ba3a5bbf17..d97dff5fab62 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -1537,8 +1537,13 @@ void mmc_power_up(struct mmc_host *host, u32 ocr) host->ios.timing = MMC_TIMING_LEGACY; mmc_set_ios(host); - /* Set signal voltage to 3.3V */ - __mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_330); + /* Try to set signal voltage to 3.3V but fall back to 1.8v or 1.2v */ + if (__mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_330) == 0) + dev_dbg(mmc_dev(host), "Initial signal voltage of 3.3v\n"); + else if (__mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180) == 0) + dev_dbg(mmc_dev(host), "Initial signal voltage of 1.8v\n"); + else if (__mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_120) == 0) + dev_dbg(mmc_dev(host), "Initial signal voltage of 1.2v\n"); /* * This delay should be sufficient to allow the power supply -- 2.11.0