linux-kernel - [PATCH 2/2] clk: sunxi-ng: sun50i: a64: Add 2x fixed post-divider to MMC module clocks

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Date:   Mon,  4 Dec 2017 13:19:12 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>
Cc:     Chen-Yu Tsai <wens@...e.org>, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: [PATCH 2/2] clk: sunxi-ng: sun50i: a64: Add 2x fixed post-divider to MMC module clocks

On the A64, the MMC module clocks are fixed in the new timing mode,
i.e. they do not have a bit to select the mode. These clocks have
a 2x divider somewhere between the clock and the MMC module.

To be consistent with other SoCs supporting the new timing mode,
we model the 2x divider as a fixed post-divider on the MMC module
clocks.

This patch adds the post-dividers to the MMC clocks.

Signed-off-by: Chen-Yu Tsai <wens@...e.org>
---
 drivers/clk/sunxi-ng/ccu-sun50i-a64.c | 57 +++++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 20 deletions(-)

diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
index 2bb4cabf802f..ee9c12cf3f08 100644
--- a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
+++ b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
@@ -400,28 +400,45 @@ static SUNXI_CCU_MP_WITH_MUX_GATE(nand_clk, "nand", mod0_default_parents, 0x080,
 				  BIT(31),	/* gate */
 				  0);
 
+/*
+ * MMC clocks are the new timing mode (see A83T & H3) variety, but without
+ * the mode switch. This means they have a 2x post divider between the clock
+ * and the MMC module. This is not documented in the manual, but is taken
+ * into consideration when setting the mmc module clocks in the BSP kernel.
+ * Without it, MMC performance is degraded.
+ *
+ * We model it here to be consistent with other SoCs supporting this mode.
+ * The alternative would be to add the 2x multiplier when setting the MMC
+ * module clock in the MMC driver, just for the A64.
+ */
 static const char * const mmc_default_parents[] = { "osc24M", "pll-periph0-2x",
 						    "pll-periph1-2x" };
-static SUNXI_CCU_MP_WITH_MUX_GATE(mmc0_clk, "mmc0", mmc_default_parents, 0x088,
-				  0, 4,		/* M */
-				  16, 2,	/* P */
-				  24, 2,	/* mux */
-				  BIT(31),	/* gate */
-				  0);
-
-static SUNXI_CCU_MP_WITH_MUX_GATE(mmc1_clk, "mmc1", mmc_default_parents, 0x08c,
-				  0, 4,		/* M */
-				  16, 2,	/* P */
-				  24, 2,	/* mux */
-				  BIT(31),	/* gate */
-				  0);
-
-static SUNXI_CCU_MP_WITH_MUX_GATE(mmc2_clk, "mmc2", mmc_default_parents, 0x090,
-				  0, 4,		/* M */
-				  16, 2,	/* P */
-				  24, 2,	/* mux */
-				  BIT(31),	/* gate */
-				  0);
+static SUNXI_CCU_MP_WITH_MUX_GATE_POSTDIV(mmc0_clk, "mmc0",
+					  mmc_default_parents, 0x088,
+					  0, 4,		/* M */
+					  16, 2,	/* P */
+					  24, 2,	/* mux */
+					  BIT(31),	/* gate */
+					  2,		/* post-div */
+					  0);
+
+static SUNXI_CCU_MP_WITH_MUX_GATE_POSTDIV(mmc1_clk, "mmc1",
+					  mmc_default_parents, 0x08c,
+					  0, 4,		/* M */
+					  16, 2,	/* P */
+					  24, 2,	/* mux */
+					  BIT(31),	/* gate */
+					  2,		/* post-div */
+					  0);
+
+static SUNXI_CCU_MP_WITH_MUX_GATE_POSTDIV(mmc2_clk, "mmc2",
+					  mmc_default_parents, 0x090,
+					  0, 4,		/* M */
+					  16, 2,	/* P */
+					  24, 2,	/* mux */
+					  BIT(31),	/* gate */
+					  2,		/* post-div */
+					  0);
 
 static const char * const ts_parents[] = { "osc24M", "pll-periph0", };
 static SUNXI_CCU_MP_WITH_MUX_GATE(ts_clk, "ts", ts_parents, 0x098,
-- 
2.15.0