[v4 01/12] clk: aspeed: Get HCLK frequency support

[Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>]

User can get correct HCLK frequency during driver probe stage
by adding the following configuration in the device tree.
"clocks = <&scu ASPEED_CLK_AHB>".

Signed-off-by: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
---
v3: Get AHB bus clock frequency from the function parameter.

 drivers/clk/aspeed/clk_ast2500.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/clk/aspeed/clk_ast2500.c b/drivers/clk/aspeed/clk_ast2500.c
index a1b4496ca2..d99964fcd7 100644
--- a/drivers/clk/aspeed/clk_ast2500.c
+++ b/drivers/clk/aspeed/clk_ast2500.c
@@ -29,6 +29,12 @@
 
 #define D2PLL_DEFAULT_RATE	(250 * 1000 * 1000)
 
+/*
+ * AXI/AHB clock selection, taken from Aspeed SDK
+ */
+#define SCU_HWSTRAP_AXIAHB_DIV_SHIFT    9
+#define SCU_HWSTRAP_AXIAHB_DIV_MASK     (0x7 << SCU_HWSTRAP_AXIAHB_DIV_SHIFT)
+
 DECLARE_GLOBAL_DATA_PTR;
 
 /*
@@ -85,6 +91,20 @@ static ulong ast2500_get_clkin(struct ast2500_scu *scu)
 			? 25 * 1000 * 1000 : 24 * 1000 * 1000;
 }
 
+static u32 ast2500_get_hclk(ulong clkin, struct ast2500_scu *scu)
+{
+	u32 hpll_reg = readl(&scu->h_pll_param);
+	ulong axi_div = 2;
+	u32 rate;
+	ulong ahb_div = 1 + ((readl(&scu->hwstrap)
+			      & SCU_HWSTRAP_AXIAHB_DIV_MASK)
+			     >> SCU_HWSTRAP_AXIAHB_DIV_SHIFT);
+
+	rate = ast2500_get_hpll_rate(clkin, hpll_reg);
+
+	return (rate / axi_div / ahb_div);
+}
+
 /**
  * Get current rate or uart clock
  *
@@ -146,6 +166,9 @@ static ulong ast2500_clk_get_rate(struct clk *clk)
 			rate = rate / apb_div;
 		}
 		break;
+	case ASPEED_CLK_AHB:
+		rate = ast2500_get_hclk(clkin, priv->scu);
+		break;
 	case ASPEED_CLK_SDIO:
 		{
 			ulong apb_div = 4 + 4 * ((readl(&priv->scu->clk_sel1)
-- 
2.25.1