mmc: mmci: add explicit clk control

On Controllers like Qcom SD card controller where cclk is mclk and mclk should
be directly controlled by the driver.

This patch adds support to control mclk directly in the driver, and also
adds explicit_mclk_control flag in variant structure giving more flexibility
to the driver.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
[Ulf Hansson] Fixed checkpatch warning
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

2 files changed, 28 insertions, 3 deletions

diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index b588810fd1a4..2e6075fdce46 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -72,6 +72,7 @@ static unsigned int fmax = 515633;
  * @pwrreg_clkgate: MMCIPOWER register must be used to gate the clock
  * @busy_detect: true if busy detection on dat0 is supported
  * @pwrreg_nopower: bits in MMCIPOWER don't controls ext. power supply
+ * @explicit_mclk_control: enable explicit mclk control in driver.
  */
 struct variant_data {
         unsigned int            clkreg;
@@ -93,6 +94,7 @@ struct variant_data {
         bool                    pwrreg_clkgate;
         bool                    busy_detect;
         bool                    pwrreg_nopower;
+        bool                    explicit_mclk_control;
 };
 
 static struct variant_data variant_arm = {
@@ -286,7 +288,9 @@ static void mmci_set_clkreg(struct mmci_host *host, unsigned int desired)
         host->cclk = 0;
 
         if (desired) {
-                if (desired >= host->mclk) {
+                if (variant->explicit_mclk_control) {
+                        host->cclk = host->mclk;
+                } else if (desired >= host->mclk) {
                         clk = MCI_CLK_BYPASS;
                         if (variant->st_clkdiv)
                                 clk |= MCI_ST_UX500_NEG_EDGE;
@@ -1327,6 +1331,17 @@ static void mmci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
         if (!ios->clock && variant->pwrreg_clkgate)
                 pwr &= ~MCI_PWR_ON;
 
+        if (host->variant->explicit_mclk_control &&
+            ios->clock != host->clock_cache) {
+                ret = clk_set_rate(host->clk, ios->clock);
+                if (ret < 0)
+                        dev_err(mmc_dev(host->mmc),
+                                "Error setting clock rate (%d)\n", ret);
+                else
+                        host->mclk = clk_get_rate(host->clk);
+        }
+        host->clock_cache = ios->clock;
+
         spin_lock_irqsave(&host->lock, flags);
 
         mmci_set_clkreg(host, ios->clock);
@@ -1502,9 +1517,12 @@ static int mmci_probe(struct amba_device *dev,
          * The ARM and ST versions of the block have slightly different
          * clock divider equations which means that the minimum divider
          * differs too.
+         * on Qualcomm like controllers get the nearest minimum clock to 100Khz
          */
         if (variant->st_clkdiv)
                 mmc->f_min = DIV_ROUND_UP(host->mclk, 257);
+        else if (variant->explicit_mclk_control)
+                mmc->f_min = clk_round_rate(host->clk, 100000);
         else
                 mmc->f_min = DIV_ROUND_UP(host->mclk, 512);
         /*
@@ -1514,9 +1532,14 @@ static int mmci_probe(struct amba_device *dev,
          * the block, of course.
          */
         if (mmc->f_max)
-                mmc->f_max = min(host->mclk, mmc->f_max);
+                mmc->f_max = variant->explicit_mclk_control ?
+                                min(variant->f_max, mmc->f_max) :
+                                min(host->mclk, mmc->f_max);
         else
-                mmc->f_max = min(host->mclk, fmax);
+                mmc->f_max = variant->explicit_mclk_control ?
+                                fmax : min(host->mclk, fmax);
+
+
         dev_dbg(mmc_dev(mmc), "clocking block at %u Hz\n", mmc->f_max);
 
         /* Get regulators and the supported OCR mask */
diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
index d38a99df1820..ef346170b241 100644
--- a/drivers/mmc/host/mmci.h
+++ b/drivers/mmc/host/mmci.h
@@ -208,6 +208,8 @@ struct mmci_host {
         spinlock_t              lock;
 
         unsigned int            mclk;
+        /* cached value of requested clk in set_ios */
+        unsigned int            clock_cache;
         unsigned int            cclk;
         u32                     pwr_reg;
         u32                     pwr_reg_add;