linux-kernel - [PATCH] clk: sunxi-ng: h3/h5: Model H3 CLK

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Date:   Wed, 28 Dec 2022 22:22:30 -0600
From:   Samuel Holland <samuel@...lland.org>
To:     Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>
Cc:     Samuel Holland <samuel@...lland.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...ts.linux.dev
Subject: [PATCH] clk: sunxi-ng: h3/h5: Model H3 CLK_DRAM as a fixed clock

The DRAM controller clock is only allowed to change frequency while the
DRAM chips are in self-refresh. To support this, changes to the CLK_DRAM
mux and divider have no effect until acknowledged by the memory dynamic
frequency scaling (MDFS) hardware inside the DRAM controller. (There is
a SDRCLK_UPD bit in DRAM_CFG_REG which should serve a similar purpose,
but this bit actually does nothing.)

However, the MDFS hardware in H3 appears to be broken. Triggering a
frequency change using the procedure from similar SoCs (A64/H5) hangs
the hardware. Additionally, the vendor BSP specifically avoids using the
MDFS hardware on H3, instead performing all DRAM PHY parameter updates
and resets in software.

Thus, it is effectively impossible to change the CLK_DRAM mux/divider,
so those features should not be modeled. Add CLK_SET_RATE_PARENT so
frequency changes apply to PLL_DDR instead.

Signed-off-by: Samuel Holland <samuel@...lland.org>
---

 drivers/clk/sunxi-ng/ccu-sun8i-h3.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/sunxi-ng/ccu-sun8i-h3.c b/drivers/clk/sunxi-ng/ccu-sun8i-h3.c
index d3fcb983c17c..bfebe8dbbe65 100644
--- a/drivers/clk/sunxi-ng/ccu-sun8i-h3.c
+++ b/drivers/clk/sunxi-ng/ccu-sun8i-h3.c
@@ -434,8 +434,13 @@ static SUNXI_CCU_GATE(usb_ohci2_clk,	"usb-ohci2",	"osc24M",
 static SUNXI_CCU_GATE(usb_ohci3_clk,	"usb-ohci3",	"osc24M",
 		      0x0cc, BIT(19), 0);
 
-static const char * const dram_parents[] = { "pll-ddr", "pll-periph0-2x" };
-static SUNXI_CCU_M_WITH_MUX(dram_clk, "dram", dram_parents,
+/* H3 has broken MDFS hardware, so the mux/divider cannot be changed. */
+static CLK_FIXED_FACTOR_HW(h3_dram_clk, "dram",
+			   &pll_ddr_clk.common.hw,
+			   1, 1, CLK_SET_RATE_PARENT | CLK_IS_CRITICAL);
+
+static const char * const h5_dram_parents[] = { "pll-ddr", "pll-periph0-2x" };
+static SUNXI_CCU_M_WITH_MUX(h5_dram_clk, "dram", h5_dram_parents,
 			    0x0f4, 0, 4, 20, 2, CLK_IS_CRITICAL);
 
 static SUNXI_CCU_GATE(dram_ve_clk,	"dram-ve",	"dram",
@@ -592,7 +597,7 @@ static struct ccu_common *sun8i_h3_ccu_clks[] = {
 	&usb_ohci1_clk.common,
 	&usb_ohci2_clk.common,
 	&usb_ohci3_clk.common,
-	&dram_clk.common,
+	&h5_dram_clk.common,
 	&dram_ve_clk.common,
 	&dram_csi_clk.common,
 	&dram_deinterlace_clk.common,
@@ -732,7 +737,7 @@ static struct clk_hw_onecell_data sun8i_h3_hw_clks = {
 		[CLK_USB_OHCI1]		= &usb_ohci1_clk.common.hw,
 		[CLK_USB_OHCI2]		= &usb_ohci2_clk.common.hw,
 		[CLK_USB_OHCI3]		= &usb_ohci3_clk.common.hw,
-		[CLK_DRAM]		= &dram_clk.common.hw,
+		[CLK_DRAM]		= &h3_dram_clk.hw,
 		[CLK_DRAM_VE]		= &dram_ve_clk.common.hw,
 		[CLK_DRAM_CSI]		= &dram_csi_clk.common.hw,
 		[CLK_DRAM_DEINTERLACE]	= &dram_deinterlace_clk.common.hw,
@@ -848,7 +853,7 @@ static struct clk_hw_onecell_data sun50i_h5_hw_clks = {
 		[CLK_USB_OHCI1]		= &usb_ohci1_clk.common.hw,
 		[CLK_USB_OHCI2]		= &usb_ohci2_clk.common.hw,
 		[CLK_USB_OHCI3]		= &usb_ohci3_clk.common.hw,
-		[CLK_DRAM]		= &dram_clk.common.hw,
+		[CLK_DRAM]		= &h5_dram_clk.common.hw,
 		[CLK_DRAM_VE]		= &dram_ve_clk.common.hw,
 		[CLK_DRAM_CSI]		= &dram_csi_clk.common.hw,
 		[CLK_DRAM_DEINTERLACE]	= &dram_deinterlace_clk.common.hw,
-- 
2.37.4