mmc: core: Fixup signal voltage switch
When switching SD and SDIO cards from 3.3V to 1.8V signal levels, the
clock should be gated for 5 ms during the step. After enabling the
clock, the host should wait for at least 1 ms before checking for
failure. Failure by the card to switch is indicated by dat[0:3] being
pulled low. The host should check for this condition and power-cycle
the card if failure is indicated.
Add a retry mechanism for the SDIO case.
If the voltage switch fails repeatedly, give up and continue the
initialization using the original voltage.
This patch places a couple of requirements on the host driver:
1) mmc_set_ios with ios.clock = 0 must gate the clock
2) mmc_power_off must actually cut the power to the card
3) The card_busy host_ops member must be implemented
if these requirements are not fulfilled, the 1.8V signal voltage switch
will still be attempted but may not be successful.
Signed-off-by: Johan Rudholm <johan.rudholm@stericsson.com>
Signed-off-by: Kevin Liu <kliu5@marvell.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Wei WANG <wei_wang@realsil.com.cn>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 9a59fcd..03134b1 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -712,6 +712,14 @@
{
int err;
u32 max_current;
+ int retries = 10;
+
+try_again:
+ if (!retries) {
+ ocr &= ~SD_OCR_S18R;
+ pr_warning("%s: Skipping voltage switch\n",
+ mmc_hostname(host));
+ }
/*
* Since we're changing the OCR value, we seem to
@@ -733,9 +741,10 @@
/*
* If the host supports one of UHS-I modes, request the card
- * to switch to 1.8V signaling level.
+ * to switch to 1.8V signaling level. If the card has failed
+ * repeatedly to switch however, skip this.
*/
- if (mmc_host_uhs(host))
+ if (retries && mmc_host_uhs(host))
ocr |= SD_OCR_S18R;
/*
@@ -746,7 +755,6 @@
if (max_current > 150)
ocr |= SD_OCR_XPC;
-try_again:
err = mmc_send_app_op_cond(host, ocr, rocr);
if (err)
return err;
@@ -758,8 +766,11 @@
if (!mmc_host_is_spi(host) && rocr &&
((*rocr & 0x41000000) == 0x41000000)) {
err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180);
- if (err) {
- ocr &= ~SD_OCR_S18R;
+ if (err == -EAGAIN) {
+ retries--;
+ goto try_again;
+ } else if (err) {
+ retries = 0;
goto try_again;
}
}