mmc: exynos_dw_mmc: Obtain and use CIU clock via CCF API

New Exynos chips should implement clock drivers using CCF framework. In
that case corresponding CCF functions can be used to get/set the clock
rates. Moreover, already existing get_mmc_clk() and set_mmc_clk() calls
are only implemented for CONFIG_CPU_V7A (i.e. ARM32 chips). In case of
ARM64 chips that config option is not defined, so build will crash on
linking stage, with errors like these:

    ld: drivers/mmc/exynos_dw_mmc.o:
      in function `exynos_dwmci_get_sclk':
      undefined reference to `get_mmc_clk'
    ld: drivers/mmc/exynos_dw_mmc.o:
      in function `exynos_dwmci_set_sclk':
      undefined reference to `set_mmc_clk'

Fix that issue by using CCF clocks API on ARM64 platforms for getting
and setting the source clock (sclk = SDCLKIN = CIU) rate. To implement
this, first extract the existing ARM32 clock control code into helper
functions with more generic signatures to abstract getting/setting the
sclk rate. Then add CCF clock support to those functions for ARM64
platforms.

Fixes: a082a2dde0 ("EXYNOS5: DWMMC: Added FDT support for DWMMC")
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>

drivers/mmc/exynos_dw_mmc.c

@@ -4,6 +4,7 @@
  * Jaehoon Chung <jh80.chung@samsung.com>
  */
 
+#include <clk.h>
 #include <dwmmc.h>
 #include <fdtdec.h>
 #include <asm/global_data.h>
@@ -15,6 +16,7 @@
 #include <asm/arch/pinmux.h>
 #include <asm/arch/power.h>
 #include <asm/gpio.h>
+#include <linux/err.h>
 #include <linux/printk.h>
 
 #define	DWMMC_MAX_CH_NUM		4
@@ -38,6 +40,7 @@ struct dwmci_exynos_priv_data {
 #ifdef CONFIG_DM_MMC
 	struct dwmci_host host;
 #endif
+	struct clk clk;
 	u32 sdr_timing;
 };
 
@@ -51,6 +54,61 @@ static struct dwmci_exynos_priv_data *exynos_dwmmc_get_priv(
 #endif
 }
 
+/**
+ * exynos_dwmmc_get_sclk - Get source clock (SDCLKIN) rate
+ * @host: MMC controller object
+ * @rate: Will contain clock rate, Hz
+ *
+ * Return: 0 on success or negative value on error
+ */
+static int exynos_dwmmc_get_sclk(struct dwmci_host *host, unsigned long *rate)
+{
+#ifdef CONFIG_CPU_V7A
+	*rate = get_mmc_clk(host->dev_index);
+#else
+	struct dwmci_exynos_priv_data *priv = exynos_dwmmc_get_priv(host);
+
+	*rate = clk_get_rate(&priv->clk);
+#endif
+
+	if (IS_ERR_VALUE(*rate))
+		return *rate;
+
+	return 0;
+}
+
+/**
+ * exynos_dwmmc_set_sclk - Set source clock (SDCLKIN) rate
+ * @host: MMC controller object
+ * @rate: Desired clock rate, Hz
+ *
+ * Return: 0 on success or negative value on error
+ */
+static int exynos_dwmmc_set_sclk(struct dwmci_host *host, unsigned long rate)
+{
+	int err;
+
+#ifdef CONFIG_CPU_V7A
+	unsigned long sclk;
+	unsigned int div;
+
+	err = exynos_dwmmc_get_sclk(host, &sclk);
+	if (err)
+		return err;
+
+	div = DIV_ROUND_UP(sclk, rate);
+	set_mmc_clk(host->dev_index, div);
+#else
+	struct dwmci_exynos_priv_data *priv = exynos_dwmmc_get_priv(host);
+
+	err = clk_set_rate(&priv->clk, rate);
+	if (err < 0)
+		return err;
+#endif
+
+	return 0;
+}
+
 /*
  * Function used as callback function to initialise the
  * CLKSEL register for every mmc channel.
@@ -68,6 +126,7 @@ unsigned int exynos_dwmci_get_clk(struct dwmci_host *host, uint freq)
 {
 	unsigned long sclk;
 	int8_t clk_div;
+	int err;
 
 	/*
 	 * Since SDCLKIN is divided inside controller by the DIVRATIO
@@ -77,7 +136,13 @@ unsigned int exynos_dwmci_get_clk(struct dwmci_host *host, uint freq)
 	 */
 	clk_div = ((dwmci_readl(host, DWMCI_CLKSEL) >> DWMCI_DIVRATIO_BIT)
 			& DWMCI_DIVRATIO_MASK) + 1;
-	sclk = get_mmc_clk(host->dev_index);
+
+	err = exynos_dwmmc_get_sclk(host, &sclk);
+	if (err) {
+		printf("DWMMC%d: failed to get clock rate (%d)\n",
+		       host->dev_index, err);
+		return 0;
+	}
 
 	/*
 	 * Assume to know divider value.
@@ -107,19 +172,19 @@ static void exynos_dwmci_board_init(struct dwmci_host *host)
 
 static int exynos_dwmci_core_init(struct dwmci_host *host)
 {
-	unsigned int div;
-	unsigned long freq, sclk;
+	unsigned long freq;
+	int err;
 
 	if (host->bus_hz)
 		freq = host->bus_hz;
 	else
 		freq = DWMMC_MAX_FREQ;
 
-	/* request mmc clock vlaue of 52MHz.  */
-	sclk = get_mmc_clk(host->dev_index);
-	div = DIV_ROUND_UP(sclk, freq);
-	/* set the clock divisor for mmc */
-	set_mmc_clk(host->dev_index, div);
+	err = exynos_dwmmc_set_sclk(host, freq);
+	if (err) {
+		printf("DWMMC%d: failed to set clock rate on probe (%d); "
+		       "continue anyway\n", host->dev_index, err);
+	}
 
 	host->name = "EXYNOS DWMMC";
 #ifdef CONFIG_EXYNOS5420
@@ -230,6 +295,12 @@ static int exynos_dwmmc_probe(struct udevice *dev)
 	struct dwmci_host *host = &priv->host;
 	int err;
 
+#ifndef CONFIG_CPU_V7A
+	err = clk_get_by_index(dev, 1, &priv->clk); /* ciu */
+	if (err)
+		return err;
+#endif
+
 	err = exynos_dwmci_get_config(dev, gd->fdt_blob, dev_of_offset(dev),
 				      host, priv);
 	if (err)