clk: thead: support changing DPU pixel clock rate

The DPU pixel clock rate corresponds to the required dot clock of the
display mode, so it needs to be tweakable.

Add support to change it, by adding generic divider setting code,
arming the code to the dpu0/dpu1 clocks, and setting the pixel clock
connected to the DPU (after a gate) to CLK_SET_RATE_PARENT to propagate
it to the dividers.

Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
Reviewed-by: Drew Fustini <fustini@kernel.org>
Signed-off-by: Drew Fustini <fustini@kernel.org>

Author: Icenowy

drivers/clk/thead/clk-th1520-ap.c

@@ -56,6 +56,7 @@ struct ccu_gate {
 
 struct ccu_div {
 	u32			enable;
+	u32			div_en;
 	struct ccu_div_internal	div;
 	struct ccu_internal	mux;
 	struct ccu_common	common;
@@ -192,6 +193,55 @@ static unsigned long ccu_div_recalc_rate(struct clk_hw *hw,
 	return rate;
 }
 
+static int ccu_div_determine_rate(struct clk_hw *hw,
+				  struct clk_rate_request *req)
+{
+	struct ccu_div *cd = hw_to_ccu_div(hw);
+	unsigned int val;
+
+	if (cd->div_en)
+		return divider_determine_rate(hw, req, NULL,
+					      cd->div.width, cd->div.flags);
+
+	regmap_read(cd->common.map, cd->common.cfg0, &val);
+	val = val >> cd->div.shift;
+	val &= GENMASK(cd->div.width - 1, 0);
+	return divider_ro_determine_rate(hw, req, NULL, cd->div.width,
+					 cd->div.flags, val);
+}
+
+static int ccu_div_set_rate(struct clk_hw *hw, unsigned long rate,
+			    unsigned long parent_rate)
+{
+	struct ccu_div *cd = hw_to_ccu_div(hw);
+	int val = divider_get_val(rate, parent_rate, NULL,
+				  cd->div.width, cd->div.flags);
+	unsigned int curr_val, reg_val;
+
+	if (val < 0)
+		return val;
+
+	regmap_read(cd->common.map, cd->common.cfg0, &reg_val);
+	curr_val = reg_val >> cd->div.shift;
+	curr_val &= GENMASK(cd->div.width - 1, 0);
+
+	if (!cd->div_en && curr_val != val)
+		return -EINVAL;
+
+	reg_val &= ~cd->div_en;
+	regmap_write(cd->common.map, cd->common.cfg0, reg_val);
+	udelay(1);
+
+	reg_val &= ~GENMASK(cd->div.width + cd->div.shift - 1, cd->div.shift);
+	reg_val |= val << cd->div.shift;
+	regmap_write(cd->common.map, cd->common.cfg0, reg_val);
+
+	reg_val |= cd->div_en;
+	regmap_write(cd->common.map, cd->common.cfg0, reg_val);
+
+	return 0;
+}
+
 static u8 ccu_div_get_parent(struct clk_hw *hw)
 {
 	struct ccu_div *cd = hw_to_ccu_div(hw);
@@ -234,7 +284,8 @@ static const struct clk_ops ccu_div_ops = {
 	.get_parent	= ccu_div_get_parent,
 	.set_parent	= ccu_div_set_parent,
 	.recalc_rate	= ccu_div_recalc_rate,
-	.determine_rate	= clk_hw_determine_rate_no_reparent,
+	.set_rate	= ccu_div_set_rate,
+	.determine_rate = ccu_div_determine_rate,
 };
 
 static void ccu_pll_disable(struct clk_hw *hw)
@@ -778,14 +829,15 @@ static struct ccu_div venc_clk = {
 };
 
 static struct ccu_div dpu0_clk = {
+	.div_en		= BIT(8),
 	.div		= TH_CCU_DIV_FLAGS(0, 8, CLK_DIVIDER_ONE_BASED),
 	.common		= {
 		.clkid          = CLK_DPU0,
 		.cfg0		= 0x1e8,
 		.hw.init	= CLK_HW_INIT_PARENTS_HW("dpu0",
 					      dpu0_pll_clk_parent,
 					      &ccu_div_ops,
-					      0),
+					      CLK_SET_RATE_UNGATE),
 	},
 };
 
@@ -794,14 +846,15 @@ static const struct clk_parent_data dpu0_clk_pd[] = {
 };
 
 static struct ccu_div dpu1_clk = {
+	.div_en		= BIT(8),
 	.div		= TH_CCU_DIV_FLAGS(0, 8, CLK_DIVIDER_ONE_BASED),
 	.common		= {
 		.clkid          = CLK_DPU1,
 		.cfg0		= 0x1ec,
 		.hw.init	= CLK_HW_INIT_PARENTS_HW("dpu1",
 					      dpu1_pll_clk_parent,
 					      &ccu_div_ops,
-					      0),
+					      CLK_SET_RATE_UNGATE),
 	},
 };
 
@@ -889,9 +942,9 @@ static CCU_GATE(CLK_GPU_CORE, gpu_core_clk, "gpu-core-clk", video_pll_clk_pd,
 static CCU_GATE(CLK_GPU_CFG_ACLK, gpu_cfg_aclk, "gpu-cfg-aclk",
 		video_pll_clk_pd, 0x0, 4, 0);
 static CCU_GATE(CLK_DPU_PIXELCLK0, dpu0_pixelclk, "dpu0-pixelclk",
-		dpu0_clk_pd, 0x0, 5, 0);
+		dpu0_clk_pd, 0x0, 5, CLK_SET_RATE_PARENT);
 static CCU_GATE(CLK_DPU_PIXELCLK1, dpu1_pixelclk, "dpu1-pixelclk",
-		dpu1_clk_pd, 0x0, 6, 0);
+		dpu1_clk_pd, 0x0, 6, CLK_SET_RATE_PARENT);
 static CCU_GATE(CLK_DPU_HCLK, dpu_hclk, "dpu-hclk", video_pll_clk_pd, 0x0,
 		7, 0);
 static CCU_GATE(CLK_DPU_ACLK, dpu_aclk, "dpu-aclk", video_pll_clk_pd, 0x0,