mmc: sdhci: add support for programmable clock mode

Host Controller v3.00 supports programmable clock mode as an optional
feature. The support for this mode is indicated by non-zero value in
bits 48-55 of the Capabilities register. If supported, the actual
value of Clock Multiplier is one more than the value provided in the
bit fields. We only set Clock Generator Select (bit 5) and SDCLK
Frequency Select (bits 8-15) of the Clock Control register in case
Preset Value Enable is not set, otherwise these fields are automatically
set by the Host Controller based on the UHS mode selected. Also, since
the maximum and minimum clock frequency in this mode can be
(Base Clock * Clock Mul) and (Base Clock * Clock Mul)/1024 respectively,
f_max and f_min have been recalculated to reflect this change.

Tested by Zhangfei Gao with a Toshiba uhs card and general hs card,
on mmp2 in SDMA mode.

Signed-off-by: Arindam Nath <arindam.nath@amd.com>
Reviewed-by: Philip Rakity <prakity@marvell.com>
Tested-by: Philip Rakity <prakity@marvell.com>
Acked-by: Zhangfei Gao <zhangfei.gao@marvell.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 66 insertions, 15 deletions

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index a1ab22415883..07cca557c4b5 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1013,8 +1013,8 @@ static void sdhci_finish_command(struct sdhci_host *host)
 
 static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
 {
-        int div;
-        u16 clk;
+        int div = 0; /* Initialized for compiler warning */
+        u16 clk = 0;
         unsigned long timeout;
 
         if (clock == host->clock)
@@ -1032,14 +1032,45 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
                 goto out;
 
         if (host->version >= SDHCI_SPEC_300) {
-                /* Version 3.00 divisors must be a multiple of 2. */
-                if (host->max_clk <= clock)
-                        div = 1;
-                else {
-                        for (div = 2; div < SDHCI_MAX_DIV_SPEC_300; div += 2) {
-                                if ((host->max_clk / div) <= clock)
-                                        break;
+                /*
+                 * Check if the Host Controller supports Programmable Clock
+                 * Mode.
+                 */
+                if (host->clk_mul) {
+                        u16 ctrl;
+
+                        /*
+                         * We need to figure out whether the Host Driver needs
+                         * to select Programmable Clock Mode, or the value can
+                         * be set automatically by the Host Controller based on
+                         * the Preset Value registers.
+                         */
+                        ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
+                        if (!(ctrl & SDHCI_CTRL_PRESET_VAL_ENABLE)) {
+                                for (div = 1; div <= 1024; div++) {
+                                        if (((host->max_clk * host->clk_mul) /
+                                              div) <= clock)
+                                                break;
+                                }
+                                /*
+                                 * Set Programmable Clock Mode in the Clock
+                                 * Control register.
+                                 */
+                                clk = SDHCI_PROG_CLOCK_MODE;
+                                div--;
+                        }
+                } else {
+                        /* Version 3.00 divisors must be a multiple of 2. */
+                        if (host->max_clk <= clock)
+                                div = 1;
+                        else {
+                                for (div = 2; div < SDHCI_MAX_DIV_SPEC_300;
+                                     div += 2) {
+                                        if ((host->max_clk / div) <= clock)
+                                                break;
+                                }
                         }
+                        div >>= 1;
                 }
         } else {
                 /* Version 2.00 divisors must be a power of 2. */
@@ -1047,10 +1078,10 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
                         if ((host->max_clk / div) <= clock)
                                 break;
                 }
+                div >>= 1;
         }
-        div >>= 1;
 
-        clk = (div & SDHCI_DIV_MASK) << SDHCI_DIVIDER_SHIFT;
+        clk |= (div & SDHCI_DIV_MASK) << SDHCI_DIVIDER_SHIFT;
         clk |= ((div & SDHCI_DIV_HI_MASK) >> SDHCI_DIV_MASK_LEN)
                 << SDHCI_DIVIDER_HI_SHIFT;
         clk |= SDHCI_CLOCK_INT_EN;
@@ -2308,17 +2339,37 @@ int sdhci_add_host(struct sdhci_host *host)
                 host->timeout_clk *= 1000;
 
         /*
+         * In case of Host Controller v3.00, find out whether clock
+         * multiplier is supported.
+         */
+        host->clk_mul = (caps[1] & SDHCI_CLOCK_MUL_MASK) >>
+                        SDHCI_CLOCK_MUL_SHIFT;
+
+        /*
+         * In case the value in Clock Multiplier is 0, then programmable
+         * clock mode is not supported, otherwise the actual clock
+         * multiplier is one more than the value of Clock Multiplier
+         * in the Capabilities Register.
+         */
+        if (host->clk_mul)
+                host->clk_mul += 1;
+
+        /*
          * Set host parameters.
          */
         mmc->ops = &sdhci_ops;
+        mmc->f_max = host->max_clk;
         if (host->ops->get_min_clock)
                 mmc->f_min = host->ops->get_min_clock(host);
-        else if (host->version >= SDHCI_SPEC_300)
-                mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_300;
-        else
+        else if (host->version >= SDHCI_SPEC_300) {
+                if (host->clk_mul) {
+                        mmc->f_min = (host->max_clk * host->clk_mul) / 1024;
+                        mmc->f_max = host->max_clk * host->clk_mul;
+                } else
+                        mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_300;
+        } else
                 mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_200;
 
-        mmc->f_max = host->max_clk;
         mmc->caps |= MMC_CAP_SDIO_IRQ | MMC_CAP_ERASE;
 
         /*