mmc: core: Prevent violation of specs while initializing cards

According to eMMC/SD/SDIO specs, the VDD (VCC) voltage level must be
maintained during the initialization sequence. If we want/need to tune
the voltage level, a complete power cycle of the card must be executed.

Most host drivers conforms to the specifications by only allowing to
change VDD voltage level at the MMC_POWER_UP state, but some also cares
about MMC_POWER_ON state, which they should'nt. This patch will not
break those drivers, but they could clean up code to better reflect
what is expected from the protocol layer.

A big re-work of the mmc_select_voltage function is done to only change
VDD voltage level if the host supports MMC_CAP2_FULL_PWR_CYCLE.
Otherwise only validation of the host and card ocr mask will be done.

A very nice side-effect of this patch is that we now don't need to
reset the negotiated ocr mask at the mmc_power_off function, since now
it will actually reflect the present voltage level, which safely can be
used at the next power up and re-initialization. Moreover, we then only
need to execute mmc_select_voltage from the attach sequence.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

4 files changed, 13 insertions, 37 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 529d2eff6095..63672aba0e98 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1358,21 +1358,20 @@ u32 mmc_select_voltage(struct mmc_host *host, u32 ocr)
         int bit;
 
         ocr &= host->ocr_avail;
+        if (!ocr) {
+                dev_warn(mmc_dev(host), "no support for card's volts\n");
+                return 0;
+        }
 
-        bit = ffs(ocr);
-        if (bit) {
-                bit -= 1;
-
+        if (host->caps2 & MMC_CAP2_FULL_PWR_CYCLE) {
+                bit = ffs(ocr) - 1;
                 ocr &= 3 << bit;
-
-                mmc_host_clk_hold(host);
-                host->ios.vdd = bit;
-                mmc_set_ios(host);
-                mmc_host_clk_release(host);
+                mmc_power_cycle(host, ocr);
         } else {
-                pr_warning("%s: host doesn't support card's voltages\n",
-                                mmc_hostname(host));
-                ocr = 0;
+                bit = fls(ocr) - 1;
+                ocr &= 3 << bit;
+                if (bit != host->ios.vdd)
+                        dev_warn(mmc_dev(host), "exceeding card's volts\n");
         }
 
         return ocr;
@@ -1571,14 +1570,6 @@ void mmc_power_off(struct mmc_host *host)
         host->ios.clock = 0;
         host->ios.vdd = 0;
 
-
-        /*
-         * Reset ocr mask to be the highest possible voltage supported for
-         * this card. This value will be used at next power up.
-         */
-        if (host->card)
-                host->card->ocr = 1 << (fls(host->ocr_avail) - 1);
-
         if (!mmc_host_is_spi(host)) {
                 host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
                 host->ios.chip_select = MMC_CS_DONTCARE;
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index eb7161c11587..18ce81a85c9b 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -1535,7 +1535,6 @@ static int mmc_resume(struct mmc_host *host)
 
         mmc_claim_host(host);
         mmc_power_up(host, host->card->ocr);
-        mmc_select_voltage(host, host->card->ocr);
         err = mmc_init_card(host, host->card->ocr, host->card);
         mmc_release_host(host);
 
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 398065c57edf..53db60a76dae 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -1103,7 +1103,6 @@ static int mmc_sd_resume(struct mmc_host *host)
 
         mmc_claim_host(host);
         mmc_power_up(host, host->card->ocr);
-        mmc_select_voltage(host, host->card->ocr);
         err = mmc_sd_init_card(host, host->card->ocr, host->card);
         mmc_release_host(host);
 
diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
index e0a135a635f5..b7c19e894dd3 100644
--- a/drivers/mmc/core/sdio.c
+++ b/drivers/mmc/core/sdio.c
@@ -987,7 +987,6 @@ static int mmc_sdio_resume(struct mmc_host *host)
         /* Restore power if needed */
         if (!mmc_card_keep_power(host)) {
                 mmc_power_up(host, host->card->ocr);
-                mmc_select_voltage(host, host->card->ocr);
                 /*
                  * Tell runtime PM core we just powered up the card,
                  * since it still believes the card is powered off.
@@ -1045,7 +1044,6 @@ static int mmc_sdio_resume(struct mmc_host *host)
 static int mmc_sdio_power_restore(struct mmc_host *host)
 {
         int ret;
-        u32 ocr, rocr;
 
         BUG_ON(!host);
         BUG_ON(!host->card);
@@ -1067,28 +1065,17 @@ static int mmc_sdio_power_restore(struct mmc_host *host)
          * for OLPC SD8686 (which expects a [CMD5,5,3,7] init sequence), and
          * harmless in other situations.
          *
-         * With these steps taken, mmc_select_voltage() is also required to
-         * restore the correct voltage setting of the card.
          */
 
         sdio_reset(host);
         mmc_go_idle(host);
         mmc_send_if_cond(host, host->ocr_avail);
 
-        ret = mmc_send_io_op_cond(host, 0, &ocr);
+        ret = mmc_send_io_op_cond(host, 0, NULL);
         if (ret)
                 goto out;
 
-        if (host->ocr_avail_sdio)
-                host->ocr_avail = host->ocr_avail_sdio;
-
-        rocr = mmc_select_voltage(host, ocr & ~0x7F);
-        if (!rocr) {
-                ret = -EINVAL;
-                goto out;
-        }
-
-        ret = mmc_sdio_init_card(host, rocr, host->card,
+        ret = mmc_sdio_init_card(host, host->card->ocr, host->card,
                                 mmc_card_keep_power(host));
         if (!ret && host->sdio_irqs)
                 mmc_signal_sdio_irq(host);