[PATCH 1/1] clk: meson: meson8b: add support for the NAND clocks

[Martin Blumenstingl <martin.blumenstingl@googlemail.com>]

This adds the NAND clocks (from the HHI_NAND_CLK_CNTL register) to the
Meson8b clock driver. There are three NAND clocks: a gate which enables
or disables the NAND clock, a mux and a divider (which divides the mux
output).
Unfortunately the public S805 datasheet does not document the mux
parents. However, the vendor kernel has a few hints for us which allows
us to make an educated guess about the clock parents. To do this we need
to have a look at set_nand_core_clk() from the vendor's NAND driver (see
[0]):
- XTAL = (4<<9) | (1<<8) | 0
- 160MHz = (0<<9) | (1<<8) | 3)
- 182MHz = (3<<9) | (1<<8) | 1)
- 212MHz = (1<<9) | (1<<8) | 3)
- 255MHz = (2<<9) | (1<<8) | 1)

While there is a comment for the XTAL parent (which indicates that it
should only be used for debugging) we have to do a bit of math for the
other parents: target_freq * divider = rate of parent clock
Bit 8 above is the enable bit, so we can ignore it here. Bits 11:9 are
the mux index and bits 6:0 are the 0-based divider (so we need to add
1). This gives us:
- mux 0 (160MHz * 4) = fclk_div4 (actual rate = 637.5MHz, off by 2.5MHz)
- mux 1 (212MHz * 4) = fclk_div3 (actual rate = 850MHz, off by 2MHz)
- mux 2 (255MHz * 2) = fclk_div5 (matches exactly 510MHz)
- mux 3 (182MHz * 2) = fclk_div7 (actual rate = 346.3MHz, off by 0.3MHz)

[0] https://github.com/khadas/linux/blob/9587681285cb/drivers/amlogic/amlnf/dev/amlnf_ctrl.c#L314

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
---
 drivers/clk/meson/meson8b.c | 53 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/clk/meson/meson8b.h |  6 ++++-
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c
index e9985503165c..b7f3cf8ed386 100644
--- a/drivers/clk/meson/meson8b.c
+++ b/drivers/clk/meson/meson8b.c
@@ -403,6 +403,53 @@ struct clk_gate meson8b_clk81 = {
 	},
 };
 
+static u32 mux_table_nand[]	= { 0, 1, 2, 3, 4 };
+
+struct clk_mux meson8b_nand_clk_sel = {
+	.reg = (void *)HHI_NAND_CLK_CNTL,
+	.mask = 0x7,
+	.shift = 9,
+	.table = mux_table_nand,
+	.flags = CLK_MUX_ROUND_CLOSEST,
+	.lock = &clk_lock,
+	.hw.init = &(struct clk_init_data){
+		.name = "nand_clk_sel",
+		.ops = &clk_mux_ops,
+		/* FIXME all other parents are unknown: */
+		.parent_names = (const char *[]){ "fclk_div4", "fclk_div3",
+			"fclk_div5", "fclk_div7", "xtal" },
+		.num_parents = 5,
+		.flags = CLK_SET_RATE_NO_REPARENT,
+	},
+};
+
+struct clk_divider meson8b_nand_clk_div = {
+	.reg = (void *)HHI_NAND_CLK_CNTL,
+	.shift = 0,
+	.width = 6,
+	.flags = CLK_DIVIDER_ROUND_CLOSEST,
+	.lock = &clk_lock,
+	.hw.init = &(struct clk_init_data){
+		.name = "nand_clk_div",
+		.ops = &clk_divider_ops,
+		.parent_names = (const char *[]){ "nand_clk_sel" },
+		.num_parents = 1,
+	},
+};
+
+struct clk_gate meson8b_nand_clk_gate = {
+	.reg = (void *)HHI_NAND_CLK_CNTL,
+	.bit_idx = 8,
+	.lock = &clk_lock,
+	.hw.init = &(struct clk_init_data){
+		.name = "nand_clk_gate",
+		.ops = &clk_gate_ops,
+		.parent_names = (const char *[]){ "nand_clk_div" },
+		.num_parents = 1,
+		.flags = CLK_SET_RATE_PARENT,
+	},
+};
+
 /* Everything Else (EE) domain gates */
 
 static MESON_GATE(meson8b_ddr, HHI_GCLK_MPEG0, 0);
@@ -584,6 +631,9 @@ static struct clk_hw_onecell_data meson8b_hw_onecell_data = {
 		[CLKID_MPLL0]		    = &meson8b_mpll0.hw,
 		[CLKID_MPLL1]		    = &meson8b_mpll1.hw,
 		[CLKID_MPLL2]		    = &meson8b_mpll2.hw,
+		[CLKID_NAND_SEL]	    = &meson8b_nand_clk_sel.hw,
+		[CLKID_NAND_DIV]	    = &meson8b_nand_clk_div.hw,
+		[CLKID_NAND_CLK]	    = &meson8b_nand_clk_gate.hw,
 	},
 	.num = CLK_NR_CLKS,
 };
@@ -679,14 +729,17 @@ static struct clk_gate *const meson8b_clk_gates[] = {
 	&meson8b_ao_ahb_sram,
 	&meson8b_ao_ahb_bus,
 	&meson8b_ao_iface,
+	&meson8b_nand_clk_gate,
 };
 
 static struct clk_mux *const meson8b_clk_muxes[] = {
 	&meson8b_mpeg_clk_sel,
+	&meson8b_nand_clk_sel,
 };
 
 static struct clk_divider *const meson8b_clk_dividers[] = {
 	&meson8b_mpeg_clk_div,
+	&meson8b_nand_clk_div,
 };
 
 static int meson8b_clkc_probe(struct platform_device *pdev)
diff --git a/drivers/clk/meson/meson8b.h b/drivers/clk/meson/meson8b.h
index 3881defc8644..cbb8001b5fe8 100644
--- a/drivers/clk/meson/meson8b.h
+++ b/drivers/clk/meson/meson8b.h
@@ -37,6 +37,7 @@
 #define HHI_GCLK_AO			0x154 /* 0x55 offset in data sheet */
 #define HHI_SYS_CPU_CLK_CNTL1		0x15c /* 0x57 offset in data sheet */
 #define HHI_MPEG_CLK_CNTL		0x174 /* 0x5d offset in data sheet */
+#define HHI_NAND_CLK_CNTL		0x25c /* 0x97 offset in data sheet */
 #define HHI_MPLL_CNTL			0x280 /* 0xa0 offset in data sheet */
 #define HHI_SYS_PLL_CNTL		0x300 /* 0xc0 offset in data sheet */
 #define HHI_VID_PLL_CNTL		0x320 /* 0xc8 offset in data sheet */
@@ -160,8 +161,11 @@
 #define CLKID_MPLL0		93
 #define CLKID_MPLL1		94
 #define CLKID_MPLL2		95
+#define CLKID_NAND_SEL		96
+#define CLKID_NAND_DIV		97
+#define CLKID_NAND_CLK		98
 
-#define CLK_NR_CLKS		96
+#define CLK_NR_CLKS		99
 
 /* include the CLKIDs that have been made part of the stable DT binding */
 #include <dt-bindings/clock/meson8b-clkc.h>
-- 
2.12.1