[PATCH v2 3/4] clk: stm32: Add clock driver for STM32F4[23]xxx devices

[Daniel Thompson <daniel.thompson@linaro.org>]

The driver supports decoding and statically modelling PLL state (i.e.
we inherit state from bootloader) and provides support for all
peripherals that support simple one-bit gated clocks. The covers all
peripherals whose clocks come from the AHB, APB1 or APB2 buses.

It has been tested (for non-regression only) on an STM32F429I-Discovery
boards. The clock counts for TIM2, USART1 and SYSTICK are all set correctly
and time and the wall clock looks OK when checked with a stopwatch.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
---
 drivers/clk/Makefile      |   1 +
 drivers/clk/clk-stm32f4.c | 364 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 365 insertions(+)
 create mode 100644 drivers/clk/clk-stm32f4.c

diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index d2d5e6c..79cd0d4 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -38,6 +38,7 @@ obj-$(CONFIG_COMMON_CLK_RK808)		+= clk-rk808.o
 obj-$(CONFIG_COMMON_CLK_S2MPS11)	+= clk-s2mps11.o
 obj-$(CONFIG_COMMON_CLK_SI5351)		+= clk-si5351.o
 obj-$(CONFIG_COMMON_CLK_SI570)		+= clk-si570.o
+obj-$(CONFIG_ARCH_STM32)		+= clk-stm32f4.o
 obj-$(CONFIG_CLK_TWL6040)		+= clk-twl6040.o
 obj-$(CONFIG_ARCH_U300)			+= clk-u300.o
 obj-$(CONFIG_ARCH_VT8500)		+= clk-vt8500.o
diff --git a/drivers/clk/clk-stm32f4.c b/drivers/clk/clk-stm32f4.c
new file mode 100644
index 0000000..68f9962
--- /dev/null
+++ b/drivers/clk/clk-stm32f4.c
@@ -0,0 +1,364 @@
+/*
+ * Author: Daniel Thompson <daniel.thompson@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/clk.h>
+#include <linux/clkdev.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/clk-provider.h>
+#include <linux/spinlock.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+
+#include <linux/debugfs.h>
+
+#define STM32F4_RCC_PLLCFGR		0x04
+#define STM32F4_RCC_CFGR		0x08
+#define STM32F4_RCC_AHB1ENR		0x30
+#define STM32F4_RCC_AHB2ENR		0x34
+#define STM32F4_RCC_AHB3ENR		0x38
+#define STM32F4_RCC_APB1ENR		0x40
+#define STM32F4_RCC_APB2ENR		0x44
+
+struct stm32f4_gate_data {
+	u8	offset;
+	u8	bit_idx;
+	const char *name;
+	const char *parent_name;
+	unsigned long flags;
+};
+
+static const struct stm32f4_gate_data stm32f4_gates[] __initconst = {
+	{ STM32F4_RCC_AHB1ENR,  0,	"gpioa",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR,  1,	"gpiob",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR,  2,	"gpioc",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR,  3,	"gpiod",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR,  4,	"gpioe",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR,  5,	"gpiof",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR,  6,	"gpiog",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR,  7,	"gpioh",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR,  8,	"gpioi",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR,  9,	"gpioj",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 10,	"gpiok",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 12,	"crc",		"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 18,	"bkpsra",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 20,	"ccmdatam",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 21,	"dma1",		"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 22,	"dma2",		"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 23,	"dma2d",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 25,	"ethmac",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 26,	"ethmactx",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 27,	"ethmacrx",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 28,	"ethmacptp",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 29,	"otghs",	"ahb_div" },
+	{ STM32F4_RCC_AHB1ENR, 30,	"otghsulpi",	"ahb_div" },
+
+	{ STM32F4_RCC_AHB2ENR,  0,	"dcmi",		"ahb_div" },
+	{ STM32F4_RCC_AHB2ENR,  4,	"cryp",		"ahb_div" },
+	{ STM32F4_RCC_AHB2ENR,  5,	"hash",		"ahb_div" },
+	{ STM32F4_RCC_AHB2ENR,  6,	"rng",		"pll48" },
+	{ STM32F4_RCC_AHB2ENR,  7,	"otgfs",	"pll48" },
+
+	{ STM32F4_RCC_AHB3ENR,  0,	"fmc",		"ahb_div",
+		CLK_IGNORE_UNUSED },
+
+	{ STM32F4_RCC_APB1ENR,  0,	"tim2",		"apb1_mul" },
+	{ STM32F4_RCC_APB1ENR,  1,	"tim3",		"apb1_mul" },
+	{ STM32F4_RCC_APB1ENR,  2,	"tim4",		"apb1_mul" },
+	{ STM32F4_RCC_APB1ENR,  3,	"tim5",		"apb1_mul" },
+	{ STM32F4_RCC_APB1ENR,  4,	"tim6",		"apb1_mul" },
+	{ STM32F4_RCC_APB1ENR,  5,	"tim7",		"apb1_mul" },
+	{ STM32F4_RCC_APB1ENR,  6,	"tim12",	"apb1_mul" },
+	{ STM32F4_RCC_APB1ENR,  7,	"tim13",	"apb1_mul" },
+	{ STM32F4_RCC_APB1ENR,  8,	"tim14",	"apb1_mul" },
+	{ STM32F4_RCC_APB1ENR, 11,	"wwdg",		"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 14,	"spi2",		"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 15,	"spi3",		"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 17,	"uart2",	"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 18,	"uart3",	"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 19,	"uart4",	"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 20,	"uart5",	"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 21,	"i2c1",		"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 22,	"i2c2",		"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 23,	"i2c3",		"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 25,	"can1",		"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 26,	"can2",		"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 28,	"pwr",		"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 29,	"dac",		"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 30,	"uart7",	"apb1_div" },
+	{ STM32F4_RCC_APB1ENR, 31,	"uart8",	"apb1_div" },
+
+	{ STM32F4_RCC_APB2ENR,  0,	"tim1",		"apb2_mul" },
+	{ STM32F4_RCC_APB2ENR,  1,	"tim8",		"apb2_mul" },
+	{ STM32F4_RCC_APB2ENR,  4,	"usart1",	"apb2_div" },
+	{ STM32F4_RCC_APB2ENR,  5,	"usart6",	"apb2_div" },
+	{ STM32F4_RCC_APB2ENR,  8,	"adc1",		"apb2_div" },
+	{ STM32F4_RCC_APB2ENR,  9,	"adc2",		"apb2_div" },
+	{ STM32F4_RCC_APB2ENR, 10,	"adc3",		"apb2_div" },
+	{ STM32F4_RCC_APB2ENR, 11,	"sdio",		"pll48" },
+	{ STM32F4_RCC_APB2ENR, 12,	"spi1",		"apb2_div" },
+	{ STM32F4_RCC_APB2ENR, 13,	"spi4",		"apb2_div" },
+	{ STM32F4_RCC_APB2ENR, 14,	"syscfg",	"apb2_div" },
+	{ STM32F4_RCC_APB2ENR, 16,	"tim9",		"apb2_mul" },
+	{ STM32F4_RCC_APB2ENR, 17,	"tim10",	"apb2_mul" },
+	{ STM32F4_RCC_APB2ENR, 18,	"tim11",	"apb2_mul" },
+	{ STM32F4_RCC_APB2ENR, 20,	"spi5",		"apb2_div" },
+	{ STM32F4_RCC_APB2ENR, 21,	"spi6",		"apb2_div" },
+	{ STM32F4_RCC_APB2ENR, 22,	"sai1",		"apb2_div" },
+	{ STM32F4_RCC_APB2ENR, 26,	"ltdc",		"apb2_div" },
+};
+
+/*
+ * MAX_CLKS is the maximum value in the enumeration below plus the combined
+ * hweight of stm32f42xx_gate_map (plus one).
+ */
+#define MAX_CLKS 74
+
+enum { SYSTICK, FCLK };
+
+/*
+ * This bitmask tells us which bit offsets (0..192) on STM32F4[23]xxx
+ * have gate bits associated with them. Its combined hweight is 71.
+ */
+static const u64 stm32f42xx_gate_map[] = { 0x000000f17ef417ff,
+					   0x0000000000000001,
+					   0x04777f33f6fec9ff };
+
+static struct clk *clks[MAX_CLKS];
+static DEFINE_SPINLOCK(stm32f4_clk_lock);
+static void __iomem *base;
+
+/*
+ * "Multiplier" device for APBx clocks.
+ *
+ * The APBx dividers are power-of-two dividers and, if *not* running in 1:1
+ * mode, they also tap out the one of the low order state bits to run the
+ * timers. ST datasheets represent this feature as a (conditional) clock
+ * multiplier.
+ */
+struct clk_apb_mul {
+	struct clk_hw hw;
+	u8 bit_idx;
+};
+
+#define to_clk_apb_mul(_hw) container_of(_hw, struct clk_apb_mul, hw)
+
+static unsigned long clk_apb_mul_recalc_rate(struct clk_hw *hw,
+					     unsigned long parent_rate)
+{
+	struct clk_apb_mul *am = to_clk_apb_mul(hw);
+
+	if (readl(base + STM32F4_RCC_CFGR) & BIT(am->bit_idx))
+		return parent_rate * 2;
+
+	return parent_rate;
+}
+
+static long clk_apb_mul_round_rate(struct clk_hw *hw, unsigned long rate,
+				   unsigned long *prate)
+{
+	struct clk_apb_mul *am = to_clk_apb_mul(hw);
+	unsigned long mult = 1;
+
+	if (readl(base + STM32F4_RCC_CFGR) & BIT(am->bit_idx))
+		mult *= 2;
+
+	if (__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT) {
+		unsigned long best_parent = rate / mult;
+
+		*prate =
+		    __clk_round_rate(__clk_get_parent(hw->clk), best_parent);
+	}
+
+	return *prate * mult;
+}
+
+static int clk_apb_mul_set_rate(struct clk_hw *hw, unsigned long rate,
+				 unsigned long parent_rate)
+{
+	return 0;
+}
+
+static struct clk_ops clk_apb_mul_factor_ops = {
+	.round_rate = clk_apb_mul_round_rate,
+	.set_rate = clk_apb_mul_set_rate,
+	.recalc_rate = clk_apb_mul_recalc_rate,
+};
+
+struct clk *clk_register_apb_mul(struct device *dev, const char *name,
+				 const char *parent_name, unsigned long flags,
+				 u8 bit_idx)
+{
+	struct clk_apb_mul *am;
+	struct clk_init_data init;
+	struct clk *clk;
+
+	am = kzalloc(sizeof(*am), GFP_KERNEL);
+	if (!am)
+		return ERR_PTR(-ENOMEM);
+
+	am->bit_idx = bit_idx;
+	am->hw.init = &init;
+
+	init.name = name;
+	init.ops = &clk_apb_mul_factor_ops;
+	init.flags = flags | CLK_IS_BASIC;
+	init.parent_names = &parent_name;
+	init.num_parents = 1;
+
+	clk = clk_register(dev, &am->hw);
+
+	if (IS_ERR(clk))
+		kfree(am);
+
+	return clk;
+}
+
+/*
+ * Decode current PLL state and (statically) model the state we inherit from
+ * the bootloader.
+ */
+static void stm32f4_rcc_register_pll(const char *hse_clk, const char *hsi_clk)
+{
+	unsigned long pllcfgr = readl(base + STM32F4_RCC_PLLCFGR);
+
+	unsigned long pllm   = pllcfgr & 0x3f;
+	unsigned long plln   = (pllcfgr >> 6) & 0x1ff;
+	unsigned long pllp   = BIT(((pllcfgr >> 16) & 3) + 1);
+	const char   *pllsrc = pllcfgr & BIT(22) ? hse_clk : hsi_clk;
+	unsigned long pllq   = (pllcfgr >> 24) & 0xf;
+
+	clk_register_fixed_factor(NULL, "vco", pllsrc, 0, plln, pllm);
+	clk_register_fixed_factor(NULL, "pll", "vco", 0, 1, pllp);
+	clk_register_fixed_factor(NULL, "pll48", "vco", 0, 1, pllq);
+}
+
+/*
+ * Converts the primary and secondary indices (as they appear in DT) to an
+ * offset into our struct clock array.
+ */
+static unsigned int stm32f4_rcc_lookup_clk_idx(u8 primary, u8 secondary)
+{
+	u64 table[ARRAY_SIZE(stm32f42xx_gate_map)];
+
+	if (primary == 1) {
+		BUG_ON(secondary > FCLK);
+		return secondary;
+	}
+
+	memcpy(table, stm32f42xx_gate_map, sizeof(table));
+
+	/* only bits set in table can be used as indices */
+	BUG_ON(secondary > 8 * sizeof(table) ||
+	       0 == (table[BIT_ULL_WORD(secondary)] & BIT_ULL_MASK(secondary)));
+
+	/* mask out bits above our current index */
+	table[BIT_ULL_WORD(secondary)] &=
+	    GENMASK_ULL(secondary % BITS_PER_LONG_LONG, 0);
+
+	return FCLK + hweight64(table[0]) +
+	       (BIT_ULL_WORD(secondary) >= 1 ? hweight64(table[1]) : 0) +
+	       (BIT_ULL_WORD(secondary) >= 2 ? hweight64(table[2]) : 0);
+}
+
+struct clk *stm32f4_rcc_lookup_clk(struct of_phandle_args *clkspec, void *data)
+{
+	return clks[stm32f4_rcc_lookup_clk_idx(clkspec->args[0],
+					       clkspec->args[1])];
+}
+
+static const char __initdata *sys_parents[] =   { "hsi", NULL, "pll" };
+
+static struct clk_div_table ahb_div_table[] = {
+	{ 0x0,   1 }, { 0x1,   1 }, { 0x2,   1 }, { 0x3,   1 },
+	{ 0x4,   1 }, { 0x5,   1 }, { 0x6,   1 }, { 0x7,   1 },
+	{ 0x8,   2 }, { 0x9,   4 }, { 0xa,   8 }, { 0xb,  16 },
+	{ 0xc,  64 }, { 0xd, 128 }, { 0xe, 256 }, { 0xf, 512 },
+	{ 0 },
+};
+
+static struct clk_div_table apb_div_table[] = {
+	{ 0,  1 }, { 0,  1 }, { 0,  1 }, { 0,  1 },
+	{ 4,  2 }, { 5,  4 }, { 6,  8 }, { 7, 16 },
+	{ 0 },
+};
+
+static void __init stm32f4_rcc_init(struct device_node *np)
+{
+	const char *hse_clk;
+	int n;
+
+	base = of_iomap(np, 0);
+	if (!base) {
+		pr_err("%s: unable to map resource", np->name);
+		return;
+	}
+
+	hse_clk = of_clk_get_parent_name(np, 0);
+
+	clk_register_fixed_rate_with_accuracy(NULL, "hsi", NULL, 0,
+			16000000, 160000);
+	stm32f4_rcc_register_pll(hse_clk, "hsi");
+
+	sys_parents[1] = hse_clk;
+	clk_register_mux_table(
+	    NULL, "sys", sys_parents, ARRAY_SIZE(sys_parents), 0,
+	    base + STM32F4_RCC_CFGR, 0, 3, 0, NULL, &stm32f4_clk_lock);
+
+	clk_register_divider_table(NULL, "ahb_div", "sys",
+				   CLK_SET_RATE_PARENT, base + STM32F4_RCC_CFGR,
+				   4, 4, 0, ahb_div_table, &stm32f4_clk_lock);
+
+	clk_register_divider_table(NULL, "apb1_div", "ahb_div",
+				   CLK_SET_RATE_PARENT, base + STM32F4_RCC_CFGR,
+				   10, 3, 0, apb_div_table, &stm32f4_clk_lock);
+	clk_register_apb_mul(NULL, "apb1_mul", "apb1_div",
+			     CLK_SET_RATE_PARENT, 12);
+
+	clk_register_divider_table(NULL, "apb2_div", "ahb_div",
+				   CLK_SET_RATE_PARENT, base + STM32F4_RCC_CFGR,
+				   13, 3, 0, apb_div_table, &stm32f4_clk_lock);
+	clk_register_apb_mul(NULL, "apb2_mul", "apb2_div",
+			     CLK_SET_RATE_PARENT, 15);
+
+	clks[SYSTICK] = clk_register_fixed_factor(NULL, "systick", "ahb_div",
+						  0, 1, 8);
+	clks[FCLK] = clk_register_fixed_factor(NULL, "fclk", "ahb_div",
+					       0, 1, 1);
+
+	for (n = 0; n < ARRAY_SIZE(stm32f4_gates); n++) {
+		const struct stm32f4_gate_data *gd = &stm32f4_gates[n];
+		unsigned int secondary =
+		    8 * (gd->offset - STM32F4_RCC_AHB1ENR) + gd->bit_idx;
+		unsigned int idx = stm32f4_rcc_lookup_clk_idx(0, secondary);
+
+		clks[idx] = clk_register_gate(
+		    NULL, gd->name, gd->parent_name, gd->flags,
+		    base + gd->offset, gd->bit_idx, 0, &stm32f4_clk_lock);
+
+		if (IS_ERR(clks[n])) {
+			pr_err("%s: Unable to register leaf clock %s\n",
+			       np->full_name, gd->name);
+			goto fail;
+		}
+	}
+
+	of_clk_add_provider(np, stm32f4_rcc_lookup_clk, NULL);
+	return;
+fail:
+	iounmap(base);
+}
+CLK_OF_DECLARE(stm32f4_rcc, "st,stm32f42xx-rcc", stm32f4_rcc_init);
-- 
2.1.0