clk: rockchip: rk3308: Support reading UART rate and clock registers

Add support to read RK3308 registers used to configure UART clocks, and
thus to get UART rate and baudrate. This fixes clock_get_rate returning
error on serial device probing. Moreover, there is no need anymore to
use 'clock-frequency' property for UART nodes in *-u-boot.dtsi files
for all cases where UART is not inited by U-Boot proper or by SPL o by
TPL code but by a preliminary external boot phase (for Rock PI S, UART
is inited by external TPL).

Signed-off-by: Massimo Pegorer <massimo.pegorer+oss@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

3 files changed, 74 insertions, 2 deletions

diff --git a/arch/arm/dts/rk3308-rock-pi-s-u-boot.dtsi b/arch/arm/dts/rk3308-rock-pi-s-u-boot.dtsi
index 09694b41e5..61415559b7 100644
--- a/arch/arm/dts/rk3308-rock-pi-s-u-boot.dtsi
+++ b/arch/arm/dts/rk3308-rock-pi-s-u-boot.dtsi
@@ -12,6 +12,4 @@
 
 &uart0 {
 	bootph-all;
-	clock-frequency = <24000000>;
-	status = "okay";
 };
diff --git a/arch/arm/include/asm/arch-rk3308/cru_rk3308.h b/arch/arm/include/asm/arch-rk3308/cru_rk3308.h
index 86c906bb0e..84b63e4d56 100644
--- a/arch/arm/include/asm/arch-rk3308/cru_rk3308.h
+++ b/arch/arm/include/asm/arch-rk3308/cru_rk3308.h
@@ -189,6 +189,21 @@ enum {
 	DCLK_VOP_DIV_SHIFT	= 0,
 	DCLK_VOP_DIV_MASK	= 0xff,
 
+	/* CRU_CLKSEL_CON10 */
+	/* CRU_CLKSEL_CON13 */
+	/* CRU_CLKSEL_CON16 */
+	/* CRU_CLKSEL_CON19 */
+	/* CRU_CLKSEL_CON22 */
+	CLK_UART_PLL_SEL_SHIFT		= 13,
+	CLK_UART_PLL_SEL_MASK		= 0x7 << CLK_UART_PLL_SEL_SHIFT,
+	CLK_UART_PLL_SEL_DPLL		= 0,
+	CLK_UART_PLL_SEL_VPLL0,
+	CLK_UART_PLL_SEL_VPLL1,
+	CLK_UART_PLL_SEL_480M,
+	CLK_UART_PLL_SEL_24M,
+	CLK_UART_DIV_CON_SHIFT		= 0,
+	CLK_UART_DIV_CON_MASK		= 0x1f << CLK_UART_DIV_CON_SHIFT,
+
 	/* CRU_CLK_SEL25_CON */
 	/* CRU_CLK_SEL26_CON */
 	/* CRU_CLK_SEL27_CON */
diff --git a/drivers/clk/rockchip/clk_rk3308.c b/drivers/clk/rockchip/clk_rk3308.c
index d27673c454..d0a3f65446 100644
--- a/drivers/clk/rockchip/clk_rk3308.c
+++ b/drivers/clk/rockchip/clk_rk3308.c
@@ -451,6 +451,58 @@ static ulong rk3308_pwm_set_clk(struct clk *clk, uint hz)
 	return rk3308_pwm_get_clk(clk);
 }
 
+static ulong rk3308_uart_get_clk(struct clk *clk)
+{
+	struct rk3308_clk_priv *priv = dev_get_priv(clk->dev);
+	struct rk3308_cru *cru = priv->cru;
+	u32 div, pll_sel, con, con_id, parent;
+
+	switch (clk->id) {
+	case SCLK_UART0:
+		con_id = 10;
+		break;
+	case SCLK_UART1:
+		con_id = 13;
+		break;
+	case SCLK_UART2:
+		con_id = 16;
+		break;
+	case SCLK_UART3:
+		con_id = 19;
+		break;
+	case SCLK_UART4:
+		con_id = 22;
+		break;
+	default:
+		printf("do not support this uart interface\n");
+		return -EINVAL;
+	}
+
+	con = readl(&cru->clksel_con[con_id]);
+	pll_sel = (con & CLK_UART_PLL_SEL_MASK) >> CLK_UART_PLL_SEL_SHIFT;
+	div = (con & CLK_UART_DIV_CON_MASK) >> CLK_UART_DIV_CON_SHIFT;
+
+	switch (pll_sel) {
+	case CLK_UART_PLL_SEL_DPLL:
+		parent = priv->dpll_hz;
+		break;
+	case CLK_UART_PLL_SEL_VPLL0:
+		parent = priv->vpll0_hz;
+		break;
+	case CLK_UART_PLL_SEL_VPLL1:
+		parent = priv->vpll0_hz;
+		break;
+	case CLK_UART_PLL_SEL_24M:
+		parent = OSC_HZ;
+		break;
+	default:
+		printf("do not support this uart pll sel\n");
+		return -EINVAL;
+	}
+
+	return DIV_TO_RATE(parent, div);
+}
+
 static ulong rk3308_vop_get_clk(struct clk *clk)
 {
 	struct rk3308_clk_priv *priv = dev_get_priv(clk->dev);
@@ -813,6 +865,13 @@ static ulong rk3308_clk_get_rate(struct clk *clk)
 	case SCLK_EMMC_SAMPLE:
 		rate = rk3308_mmc_get_clk(clk);
 		break;
+	case SCLK_UART0:
+	case SCLK_UART1:
+	case SCLK_UART2:
+	case SCLK_UART3:
+	case SCLK_UART4:
+		rate = rk3308_uart_get_clk(clk);
+		break;
 	case SCLK_I2C0:
 	case SCLK_I2C1:
 	case SCLK_I2C2: