On 12/7/2012 9:49 PM, Johan Rudholm wrote:
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
if these requirements are not fulfilled, the 1.8V signal voltage switch
may not be successful.
Signed-off-by: Johan Rudholm <johan.rudholm@xxxxxxxxxxxxxx>
---
drivers/mmc/core/core.c | 35 +++++++++++++++++++++++++++++++++++
drivers/mmc/core/sd.c | 26 +++++++++++++++++++++-----
drivers/mmc/core/sdio.c | 25 +++++++++++++++++++++++--
3 files changed, 79 insertions(+), 7 deletions(-)
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 285f064..c9a7a8a 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1246,8 +1246,43 @@ int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage, bool cmd11
host->ios.signal_voltage = signal_voltage;
if (host->ops->start_signal_voltage_switch) {
+ u32 clock;
+
mmc_host_clk_hold(host);
+ /*
+ * During a signal voltage level switch, the clock must be gated
+ * for a certain period of time according to the SD spec
+ */
+ if (cmd11) {
+ clock = host->ios.clock;
+ host->ios.clock = 0;
+ mmc_set_ios(host);
+ }
+
err = host->ops->start_signal_voltage_switch(host, &host->ios);
Shouldn't you fix all the existing host drivers who have already
implemented start_signal_voltage_switch host ops? If you don't change
them as part of this patch then
i afraid UHS functionality would be broken on those platforms. Also,
it's not just changing the start_signal_voltage_switch hot op
implementation, you may also need to add card_busy() host op
implementation for those drivers.
+
+ if (err && cmd11) {
+ host->ios.clock = clock;
+ mmc_set_ios(host);
+ } else if (cmd11) {
+ /* Keep clock gated for at least 5 ms */
+ mmc_delay(5);
+ host->ios.clock = clock;
+ mmc_set_ios(host);
+
+ /* Wait for at least 1 ms according to spec */
+ mmc_delay(1);
+
+ /*
+ * Failure to switch is indicated by the card holding
+ * dat[0:3] low
+ */
+ if (!host->ops->card_busy)
+ pr_warning("%s: cannot verify signal voltage switch\n",
+ mmc_hostname(host));
+ else if (host->ops->card_busy(host))
+ err = -EAGAIN;
+ }
mmc_host_clk_release(host);
}
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 74972c2..eb299bc 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -713,6 +713,14 @@ int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid, u32 *rocr)
{
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
@@ -734,9 +742,10 @@ int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid, u32 *rocr)
/*
* 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 (host->caps & (MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25 |
+ if (retries && host->caps & (MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25 |
MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR104 | MMC_CAP_UHS_DDR50))
ocr |= SD_OCR_S18R;
@@ -748,7 +757,6 @@ int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid, u32 *rocr)
if (max_current > 150)
ocr |= SD_OCR_XPC;
-try_again:
err = mmc_send_app_op_cond(host, ocr, rocr);
if (err)
return err;
@@ -760,8 +768,16 @@ try_again:
if (!mmc_host_is_spi(host) && rocr &&
((*rocr & 0x41000000) == 0x41000000)) {
err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180, true);
- if (err) {
- ocr &= ~SD_OCR_S18R;
+ if (err == -EAGAIN) {
+ /* Power cycle card */
+ pr_debug("%s: Signal voltage switch failed, "
+ "power cycling card (retries = %d)\n",
+ mmc_hostname(host), retries);
+ mmc_power_cycle(host);
+ retries--;
+ goto try_again;
+ } else if (err) {
+ retries = 0;
goto try_again;
}
}
diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
index 2273ce6..573ab06 100644
--- a/drivers/mmc/core/sdio.c
+++ b/drivers/mmc/core/sdio.c
@@ -583,10 +583,19 @@ static int mmc_sdio_init_card(struct mmc_host *host, u32 ocr,
{
struct mmc_card *card;
int err;
+ int retries = 10;
BUG_ON(!host);
WARN_ON(!host->claimed);
+try_again:
+ if (!retries) {
+ pr_warning("%s: Skipping voltage switch\n",
+ mmc_hostname(host));
+ ocr &= ~R4_18V_PRESENT;
+ host->ocr &= ~R4_18V_PRESENT;
+ }
+
/*
* Inform the card of the voltage
*/
@@ -645,14 +654,26 @@ static int mmc_sdio_init_card(struct mmc_host *host, u32 ocr,
* systems that claim 1.8v signalling in fact do not support
* it.
*/
- if ((ocr & R4_18V_PRESENT) &&
+ if (!powered_resume && (ocr & R4_18V_PRESENT) &&
(host->caps &
(MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25 |
MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR104 |
MMC_CAP_UHS_DDR50))) {
err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180,
true);
- if (err) {
+ if (err == -EAGAIN) {
+ /* Power cycle card */
+ pr_debug("%s: Signal voltage switch failed, "
+ "power cycling card (retries = %d)\n",
+ mmc_hostname(host), retries);
+ mmc_power_cycle(host);
+ sdio_reset(host);
+ mmc_go_idle(host);
+ mmc_send_if_cond(host, host->ocr_avail);
+ mmc_remove_card(card);
+ retries--;
+ goto try_again;
+ } else if (err) {
ocr &= ~R4_18V_PRESENT;
host->ocr &= ~R4_18V_PRESENT;
}
--
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