[PATCH] spi: meson-spicc: add a linear clock divider support

[Sunny Luo]

The SPICC controller in Meson-AXG SoC is capable of using
a linear clock divider to reach a much fine tuned range of clocks,
while the old controller only use a power of two clock divider,
result at a more coarse clock range.

Also convert the clock registration into Common Clock Framework.

Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
Signed-off-by: Yixun Lan <yixun.lan@xxxxxxxxxxx>
Signed-off-by: Sunny Luo <sunny.luo@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200312133131.26430-4-narmstrong@xxxxxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
 drivers/spi/Kconfig           |   1 +
 drivers/spi/spi-meson-spicc.c | 204 +++++++++++++++++++++++++++-------
 2 files changed, 165 insertions(+), 40 deletions(-)

diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index c33ca96b44de..efce98e9844e 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -428,6 +428,7 @@ config SPI_FSL_ESPI
 
 config SPI_MESON_SPICC
 	tristate "Amlogic Meson SPICC controller"
+	depends on COMMON_CLK
 	depends on ARCH_MESON || COMPILE_TEST
 	help
 	  This enables master mode support for the SPICC (SPI communication
diff --git a/drivers/spi/spi-meson-spicc.c b/drivers/spi/spi-meson-spicc.c
index ba70ef94a82a..bd434d9055d9 100644
--- a/drivers/spi/spi-meson-spicc.c
+++ b/drivers/spi/spi-meson-spicc.c
@@ -116,6 +116,9 @@
 #define SPICC_DWADDR	0x24	/* Write Address of DMA */
 
 #define SPICC_ENH_CTL0	0x38	/* Enhanced Feature */
+#define SPICC_ENH_CLK_CS_DELAY_MASK	GENMASK(15, 0)
+#define SPICC_ENH_DATARATE_MASK		GENMASK(23, 16)
+#define SPICC_ENH_DATARATE_EN		BIT(24)
 #define SPICC_ENH_MOSI_OEN		BIT(25)
 #define SPICC_ENH_CLK_OEN		BIT(26)
 #define SPICC_ENH_CS_OEN		BIT(27)
@@ -130,6 +133,7 @@
 
 struct meson_spicc_data {
 	bool				has_oen;
+	bool				has_enhance_clk_div;
 };
 
 struct meson_spicc_device {
@@ -137,6 +141,7 @@ struct meson_spicc_device {
 	struct platform_device		*pdev;
 	void __iomem			*base;
 	struct clk			*core;
+	struct clk			*clk;
 	struct spi_message		*message;
 	struct spi_transfer		*xfer;
 	const struct meson_spicc_data	*data;
@@ -322,40 +327,6 @@ static irqreturn_t meson_spicc_irq(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
-static u32 meson_spicc_setup_speed(struct meson_spicc_device *spicc, u32 conf,
-				   u32 speed)
-{
-	unsigned long parent, value;
-	unsigned int i, div;
-
-	parent = clk_get_rate(spicc->core);
-
-	/* Find closest inferior/equal possible speed */
-	for (i = 0 ; i < 7 ; ++i) {
-		/* 2^(data_rate+2) */
-		value = parent >> (i + 2);
-
-		if (value <= speed)
-			break;
-	}
-
-	/* If provided speed it lower than max divider, use max divider */
-	if (i > 7) {
-		div = 7;
-		dev_warn_once(&spicc->pdev->dev, "unable to get close to speed %u\n",
-			      speed);
-	} else
-		div = i;
-
-	dev_dbg(&spicc->pdev->dev, "parent %lu, speed %u -> %lu (%u)\n",
-		parent, speed, value, div);
-
-	conf &= ~SPICC_DATARATE_MASK;
-	conf |= FIELD_PREP(SPICC_DATARATE_MASK, div);
-
-	return conf;
-}
-
 static void meson_spicc_setup_xfer(struct meson_spicc_device *spicc,
 				   struct spi_transfer *xfer)
 {
@@ -364,9 +335,6 @@ static void meson_spicc_setup_xfer(struct meson_spicc_device *spicc,
 	/* Read original configuration */
 	conf = conf_orig = readl_relaxed(spicc->base + SPICC_CONREG);
 
-	/* Select closest divider */
-	conf = meson_spicc_setup_speed(spicc, conf, xfer->speed_hz);
-
 	/* Setup word width */
 	conf &= ~SPICC_BITLENGTH_MASK;
 	conf |= FIELD_PREP(SPICC_BITLENGTH_MASK,
@@ -375,6 +343,8 @@ static void meson_spicc_setup_xfer(struct meson_spicc_device *spicc,
 	/* Ignore if unchanged */
 	if (conf != conf_orig)
 		writel_relaxed(conf, spicc->base + SPICC_CONREG);
+
+	clk_set_rate(spicc->clk, xfer->speed_hz);
 }
 
 static int meson_spicc_transfer_one(struct spi_master *master,
@@ -481,9 +451,6 @@ static int meson_spicc_unprepare_transfer(struct spi_master *master)
 	/* Disable all IRQs */
 	writel(0, spicc->base + SPICC_INTREG);
 
-	/* Disable controller */
-	writel_bits_relaxed(SPICC_ENABLE, 0, spicc->base + SPICC_CONREG);
-
 	device_reset_optional(&spicc->pdev->dev);
 
 	return 0;
@@ -502,6 +469,152 @@ static void meson_spicc_cleanup(struct spi_device *spi)
 	spi->controller_state = NULL;
 }
 
+/*
+ * The Clock Mux
+ *            x-----------------x   x------------x    x------\
+ *        |---| pow2 fixed div  |---| pow2 div   |----|      |
+ *        |   x-----------------x   x------------x    |      |
+ * src ---|                                           | mux  |-- out
+ *        |   x-----------------x   x------------x    |      |
+ *        |---| enh fixed div   |---| enh div    |0---|      |
+ *            x-----------------x   x------------x    x------/
+ *
+ * Clk path for GX series:
+ *    src -> pow2 fixed div -> pow2 div -> out
+ *
+ * Clk path for AXG series:
+ *    src -> pow2 fixed div -> pow2 div -> mux -> out
+ *    src -> enh fixed div -> enh div -> mux -> out
+ */
+
+static int meson_spicc_clk_init(struct meson_spicc_device *spicc)
+{
+	struct device *dev = &spicc->pdev->dev;
+	struct clk_fixed_factor *pow2_fixed_div, *enh_fixed_div;
+	struct clk_divider *pow2_div, *enh_div;
+	struct clk_mux *mux;
+	struct clk_init_data init;
+	struct clk *clk;
+	struct clk_parent_data parent_data[2];
+	char name[64];
+
+	memset(&init, 0, sizeof(init));
+	memset(&parent_data, 0, sizeof(parent_data));
+
+	init.parent_data = parent_data;
+
+	/* algorithm for pow2 div: rate = freq / 4 / (2 ^ N) */
+
+	pow2_fixed_div = devm_kzalloc(dev, sizeof(*pow2_fixed_div), GFP_KERNEL);
+	if (!pow2_fixed_div)
+		return -ENOMEM;
+
+	snprintf(name, sizeof(name), "%s#pow2_fixed_div", dev_name(dev));
+	init.name = name;
+	init.ops = &clk_fixed_factor_ops;
+	init.flags = 0;
+	parent_data[0].hw = __clk_get_hw(spicc->core);
+	init.num_parents = 1;
+
+	pow2_fixed_div->mult = 1,
+	pow2_fixed_div->div = 4,
+	pow2_fixed_div->hw.init = &init;
+
+	clk = devm_clk_register(dev, &pow2_fixed_div->hw);
+	if (WARN_ON(IS_ERR(clk)))
+		return PTR_ERR(clk);
+
+	pow2_div = devm_kzalloc(dev, sizeof(*pow2_div), GFP_KERNEL);
+	if (!pow2_div)
+		return -ENOMEM;
+
+	snprintf(name, sizeof(name), "%s#pow2_div", dev_name(dev));
+	init.name = name;
+	init.ops = &clk_divider_ops;
+	init.flags = CLK_SET_RATE_PARENT;
+	parent_data[0].hw = &pow2_fixed_div->hw;
+	init.num_parents = 1;
+
+	pow2_div->shift = 16,
+	pow2_div->width = 3,
+	pow2_div->flags = CLK_DIVIDER_POWER_OF_TWO,
+	pow2_div->reg = spicc->base + SPICC_CONREG;
+	pow2_div->hw.init = &init;
+
+	clk = devm_clk_register(dev, &pow2_div->hw);
+	if (WARN_ON(IS_ERR(clk)))
+		return PTR_ERR(clk);
+
+	if (!spicc->data->has_enhance_clk_div) {
+		spicc->clk = clk;
+		return 0;
+	}
+
+	/* algorithm for enh div: rate = freq / 2 / (N + 1) */
+
+	enh_fixed_div = devm_kzalloc(dev, sizeof(*enh_fixed_div), GFP_KERNEL);
+	if (!enh_fixed_div)
+		return -ENOMEM;
+
+	snprintf(name, sizeof(name), "%s#enh_fixed_div", dev_name(dev));
+	init.name = name;
+	init.ops = &clk_fixed_factor_ops;
+	init.flags = 0;
+	parent_data[0].hw = __clk_get_hw(spicc->core);
+	init.num_parents = 1;
+
+	enh_fixed_div->mult = 1,
+	enh_fixed_div->div = 2,
+	enh_fixed_div->hw.init = &init;
+
+	clk = devm_clk_register(dev, &enh_fixed_div->hw);
+	if (WARN_ON(IS_ERR(clk)))
+		return PTR_ERR(clk);
+
+	enh_div = devm_kzalloc(dev, sizeof(*enh_div), GFP_KERNEL);
+	if (!enh_div)
+		return -ENOMEM;
+
+	snprintf(name, sizeof(name), "%s#enh_div", dev_name(dev));
+	init.name = name;
+	init.ops = &clk_divider_ops;
+	init.flags = CLK_SET_RATE_PARENT;
+	parent_data[0].hw = &enh_fixed_div->hw;
+	init.num_parents = 1;
+
+	enh_div->shift	= 16,
+	enh_div->width	= 8,
+	enh_div->reg = spicc->base + SPICC_ENH_CTL0;
+	enh_div->hw.init = &init;
+
+	clk = devm_clk_register(dev, &enh_div->hw);
+	if (WARN_ON(IS_ERR(clk)))
+		return PTR_ERR(clk);
+
+	mux = devm_kzalloc(dev, sizeof(*mux), GFP_KERNEL);
+	if (!mux)
+		return -ENOMEM;
+
+	snprintf(name, sizeof(name), "%s#sel", dev_name(dev));
+	init.name = name;
+	init.ops = &clk_mux_ops;
+	parent_data[0].hw = &pow2_div->hw;
+	parent_data[1].hw = &enh_div->hw;
+	init.num_parents = 2;
+	init.flags = CLK_SET_RATE_PARENT;
+
+	mux->mask = 0x1,
+	mux->shift = 24,
+	mux->reg = spicc->base + SPICC_ENH_CTL0;
+	mux->hw.init = &init;
+
+	spicc->clk = devm_clk_register(dev, &mux->hw);
+	if (WARN_ON(IS_ERR(spicc->clk)))
+		return PTR_ERR(spicc->clk);
+
+	return 0;
+}
+
 static int meson_spicc_probe(struct platform_device *pdev)
 {
 	struct spi_master *master;
@@ -533,6 +646,10 @@ static int meson_spicc_probe(struct platform_device *pdev)
 		goto out_master;
 	}
 
+	/* Set master mode and enable controller */
+	writel_relaxed(SPICC_ENABLE | SPICC_MODE_MASTER,
+		       spicc->base + SPICC_CONREG);
+
 	/* Disable all IRQs */
 	writel_relaxed(0, spicc->base + SPICC_INTREG);
 
@@ -584,6 +701,12 @@ static int meson_spicc_probe(struct platform_device *pdev)
 
 	meson_spicc_oen_enable(spicc);
 
+	ret = meson_spicc_clk_init(spicc);
+	if (ret) {
+		dev_err(&pdev->dev, "clock registration failed\n");
+		goto out_master;
+	}
+
 	ret = devm_spi_register_master(&pdev->dev, master);
 	if (ret) {
 		dev_err(&pdev->dev, "spi master registration failed\n");
@@ -618,6 +741,7 @@ static const struct meson_spicc_data meson_spicc_gx_data = {
 
 static const struct meson_spicc_data meson_spicc_axg_data = {
 	.has_oen		= true,
+	.has_enhance_clk_div	= true,
 };
 
 static const struct of_device_id meson_spicc_of_match[] = {
-- 
2.20.1