[PATCH 27/42] mmc: exynos_dw_mmc: Refactor fixed CIU clock divider

[Sam Protsenko]

Some chips like Exynos4412 have fixed internal CIU clock divider.
Instead of reading it from non-standard "div" dts property, store its
value in the driver internally, in static chip data associated with
corresponding compatible. This makes it possible to avoid using
host->div for storing it, so the latter can be removed safely. Also
create a helper function called exynos_dwmmc_get_ciu_div() for getting
the current div value: in case the fixed div is provided in the chip
data it will be used, otherwise the current div value is being read from
CLKSEL register.

The insights for this change were taken from dw_mmc-exynos.c driver in
Linux kernel.

No functional change.

Signed-off-by: Sam Protsenko <semen.protsenko at linaro.org>
---
 drivers/mmc/ca_dw_mmc.c     |  2 +-
 drivers/mmc/exynos_dw_mmc.c | 43 +++++++++++++++++++++++++------------
 include/dwmmc.h             |  2 --
 3 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/drivers/mmc/ca_dw_mmc.c b/drivers/mmc/ca_dw_mmc.c
index a17ed8c11cbe..342e09d02306 100644
--- a/drivers/mmc/ca_dw_mmc.c
+++ b/drivers/mmc/ca_dw_mmc.c
@@ -87,7 +87,7 @@ unsigned int ca_dwmci_get_mmc_clock(struct dwmci_host *host, uint freq)
 		clk_div = 1;
 	}
 
-	return SD_SCLK_MAX / clk_div / (host->div + 1);
+	return SD_SCLK_MAX / clk_div;
 }
 
 static int ca_dwmmc_of_to_plat(struct udevice *dev)
diff --git a/drivers/mmc/exynos_dw_mmc.c b/drivers/mmc/exynos_dw_mmc.c
index edf8fbc7d734..646302f54ae6 100644
--- a/drivers/mmc/exynos_dw_mmc.c
+++ b/drivers/mmc/exynos_dw_mmc.c
@@ -24,6 +24,8 @@
 #define	DWMMC_MMC0_SDR_TIMING_VAL	0x03030001
 #define	DWMMC_MMC2_SDR_TIMING_VAL	0x03020001
 
+#define EXYNOS4412_FIXED_CIU_CLK_DIV	4
+
 #ifdef CONFIG_DM_MMC
 #include <dm.h>
 DECLARE_GLOBAL_DATA_PTR;
@@ -37,6 +39,7 @@ struct exynos_mmc_plat {
 /* Chip specific data */
 struct exynos_dwmmc_variant {
 	u32 clksel;		/* CLKSEL register offset */
+	u8 div;			/* (optional) fixed clock divider value: 0..7 */
 };
 
 /* Exynos implmentation specific drver private data */
@@ -127,12 +130,18 @@ static int exynos_dwmci_clksel(struct dwmci_host *host)
 	return 0;
 }
 
-unsigned int exynos_dwmci_get_clk(struct dwmci_host *host, uint freq)
+/**
+ * exynos_dwmmc_get_ciu_div - Get internal clock divider value
+ * @host: MMC controller object
+ *
+ * Returns: Divider value, in range of 1..8
+ */
+static u8 exynos_dwmmc_get_ciu_div(struct dwmci_host *host)
 {
 	struct dwmci_exynos_priv_data *priv = exynos_dwmmc_get_priv(host);
-	unsigned long sclk;
-	int8_t clk_div;
-	int err;
+
+	if (priv->chip->div)
+		return priv->chip->div + 1;
 
 	/*
 	 * Since SDCLKIN is divided inside controller by the DIVRATIO
@@ -140,9 +149,17 @@ unsigned int exynos_dwmci_get_clk(struct dwmci_host *host, uint freq)
 	 * clock value to calculate the CLKDIV value.
 	 * as per user manual:cclk_in = SDCLKIN / (DIVRATIO + 1)
 	 */
-	clk_div = ((dwmci_readl(host, priv->chip->clksel) >> DWMCI_DIVRATIO_BIT)
-			& DWMCI_DIVRATIO_MASK) + 1;
+	return ((dwmci_readl(host, priv->chip->clksel) >> DWMCI_DIVRATIO_BIT)
+				& DWMCI_DIVRATIO_MASK) + 1;
+}
 
+unsigned int exynos_dwmci_get_clk(struct dwmci_host *host, uint freq)
+{
+	unsigned long sclk;
+	u8 clk_div;
+	int err;
+
+	clk_div = exynos_dwmmc_get_ciu_div(host);
 	err = exynos_dwmmc_get_sclk(host, &sclk);
 	if (err) {
 		printf("DWMMC%d: failed to get clock rate (%d)\n",
@@ -150,11 +167,7 @@ unsigned int exynos_dwmci_get_clk(struct dwmci_host *host, uint freq)
 		return 0;
 	}
 
-	/*
-	 * Assume to know divider value.
-	 * When clock unit is broken, need to set "host->div"
-	 */
-	return sclk / clk_div / (host->div + 1);
+	return sclk / clk_div;
 }
 
 static void exynos_dwmci_board_init(struct dwmci_host *host)
@@ -270,8 +283,10 @@ static int exynos_dwmmc_of_to_plat(struct udevice *dev)
 		return -EINVAL;
 	}
 
-	/* Extract the timing info from the node */
-	div = dev_read_u32_default(dev, "samsung,dw-mshc-ciu-div", 0);
+	if (priv->chip->div)
+		div = priv->chip->div;
+	else
+		div = dev_read_u32_default(dev, "samsung,dw-mshc-ciu-div", 0);
 	err = dev_read_u32_array(dev, "samsung,dw-mshc-sdr-timing", timing, 2);
 	if (err) {
 		printf("DWMMC%d: Can't get sdr-timings\n", host->dev_index);
@@ -292,7 +307,6 @@ static int exynos_dwmmc_of_to_plat(struct udevice *dev)
 
 	host->fifo_depth = dev_read_u32_default(dev, "fifo-depth", 0);
 	host->bus_hz = dev_read_u32_default(dev, "bus_hz", 0);
-	host->div = dev_read_u32_default(dev, "div", 0);
 
 	return 0;
 }
@@ -334,6 +348,7 @@ static int exynos_dwmmc_bind(struct udevice *dev)
 
 static const struct exynos_dwmmc_variant exynos4_drv_data = {
 	.clksel	= DWMCI_CLKSEL,
+	.div	= EXYNOS4412_FIXED_CIU_CLK_DIV - 1,
 };
 
 static const struct exynos_dwmmc_variant exynos5_drv_data = {
diff --git a/include/dwmmc.h b/include/dwmmc.h
index e17884ade7e6..c69c7952b930 100644
--- a/include/dwmmc.h
+++ b/include/dwmmc.h
@@ -184,7 +184,6 @@ struct dwmci_idmac_regs {
  * @caps:	Capabilities - see MMC_MODE_...
  * @clock:	Current clock frequency (after internal divider), Hz
  * @bus_hz:	Bus speed in Hz, if @get_mmc_clk() is NULL
- * @div:	Arbitrary clock divider value for use by controller
  * @dev_index:	Arbitrary device index for use by controller
  * @dev_id:	Arbitrary device ID for use by controller
  * @buswidth:	Bus width in bits (8 or 4)
@@ -205,7 +204,6 @@ struct dwmci_host {
 	unsigned int caps;
 	unsigned int clock;
 	unsigned int bus_hz;
-	unsigned int div;
 	int dev_index;
 	int dev_id;
 	int buswidth;
-- 
2.39.2