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>

3 files changed, 107 insertions, 17 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index bb794c784597..e41badbf9b50 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1340,6 +1340,7 @@ int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage)
 {
         struct mmc_command cmd = {0};
         int err = 0;
+        u32 clock;
 
         BUG_ON(!host);
 
@@ -1347,20 +1348,82 @@ int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage)
          * Send CMD11 only if the request is to switch the card to
          * 1.8V signalling.
          */
-        if (signal_voltage != MMC_SIGNAL_VOLTAGE_330) {
-                cmd.opcode = SD_SWITCH_VOLTAGE;
-                cmd.arg = 0;
-                cmd.flags = MMC_RSP_R1 | MMC_CMD_AC;
+        if (signal_voltage == MMC_SIGNAL_VOLTAGE_330)
+                return __mmc_set_signal_voltage(host, signal_voltage);
 
-                err = mmc_wait_for_cmd(host, &cmd, 0);
-                if (err)
-                        return err;
+        /*
+         * If we cannot switch voltages, return failure so the caller
+         * can continue without UHS mode
+         */
+        if (!host->ops->start_signal_voltage_switch)
+                return -EPERM;
+        if (!host->ops->card_busy)
+                pr_warning("%s: cannot verify signal voltage switch\n",
+                                mmc_hostname(host));
+
+        cmd.opcode = SD_SWITCH_VOLTAGE;
+        cmd.arg = 0;
+        cmd.flags = MMC_RSP_R1 | MMC_CMD_AC;
+
+        err = mmc_wait_for_cmd(host, &cmd, 0);
+        if (err)
+                return err;
 
-                if (!mmc_host_is_spi(host) && (cmd.resp[0] & R1_ERROR))
-                        return -EIO;
+        if (!mmc_host_is_spi(host) && (cmd.resp[0] & R1_ERROR))
+                return -EIO;
+
+        mmc_host_clk_hold(host);
+        /*
+         * The card should drive cmd and dat[0:3] low immediately
+         * after the response of cmd11, but wait 1 ms to be sure
+         */
+        mmc_delay(1);
+        if (host->ops->card_busy && !host->ops->card_busy(host)) {
+                err = -EAGAIN;
+                goto power_cycle;
         }
+        /*
+         * During a signal voltage level switch, the clock must be gated
+         * for 5 ms according to the SD spec
+         */
+        clock = host->ios.clock;
+        host->ios.clock = 0;
+        mmc_set_ios(host);
 
-        return __mmc_set_signal_voltage(host, signal_voltage);
+        if (__mmc_set_signal_voltage(host, signal_voltage)) {
+                /*
+                 * Voltages may not have been switched, but we've already
+                 * sent CMD11, so a power cycle is required anyway
+                 */
+                err = -EAGAIN;
+                goto power_cycle;
+        }
+
+        /* 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 && host->ops->card_busy(host))
+                err = -EAGAIN;
+
+power_cycle:
+        if (err) {
+                pr_debug("%s: Signal voltage switch failed, "
+                        "power cycling card\n", mmc_hostname(host));
+                mmc_power_cycle(host);
+        }
+
+        mmc_host_clk_release(host);
+
+        return err;
 }
 
 /*
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 9a59fcd55a75..03134b1e563c 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -712,6 +712,14 @@ 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
@@ -733,9 +741,10 @@ 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 (mmc_host_uhs(host))
+        if (retries && mmc_host_uhs(host))
                 ocr |= SD_OCR_S18R;
 
         /*
@@ -746,7 +755,6 @@ 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;
@@ -758,8 +766,11 @@ try_again:
         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;
                 }
         }
diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
index 1a726aef211d..aa0719a4dfd1 100644
--- a/drivers/mmc/core/sdio.c
+++ b/drivers/mmc/core/sdio.c
@@ -584,10 +584,19 @@ 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
          */
@@ -646,9 +655,16 @@ 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) && mmc_host_uhs(host)) {
+        if (!powered_resume && (ocr & R4_18V_PRESENT) && mmc_host_uhs(host)) {
                 err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180);
-                if (err) {
+                if (err == -EAGAIN) {
+                        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;
                 }