[RFC PATCH 14/16] clk: hifiberry-dacpro: toggle GPIOs on prepare/unprepare

[Pierre-Louis Bossart]

Now that the PCM512x driver exposes GPIOs, we can set their values as
needed in this clk driver (instead of doing nothing).

This clk driver does not have access to the codec regmap, so it only
toggles GPIOs. The user (typically a machine driver) should verify
that the clocks are present by testing the PCM512x_RATE4_DET register
(reports if the sclk is seen by the codec).

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 drivers/clk/clk-hifiberry-dacpro.c | 110 +++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)

diff --git a/drivers/clk/clk-hifiberry-dacpro.c b/drivers/clk/clk-hifiberry-dacpro.c
index 36210f52c624..f1f5af260083 100644
--- a/drivers/clk/clk-hifiberry-dacpro.c
+++ b/drivers/clk/clk-hifiberry-dacpro.c
@@ -9,6 +9,8 @@
 
 #include <linux/clk-provider.h>
 #include <linux/clkdev.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/machine.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -20,16 +22,35 @@
 /* Clock rate of CLK48EN attached to GPIO3 pin */
 #define CLK_48EN_RATE 24576000UL
 
+static struct gpiod_lookup_table pcm512x_gpios_table = {
+	/* .dev_id set during probe */
+	.table = {
+		GPIO_LOOKUP("pcm512x-gpio", 2, "PCM512x-GPIO3", GPIO_ACTIVE_HIGH),
+		GPIO_LOOKUP("pcm512x-gpio", 5, "PCM512x-GPIO6", GPIO_ACTIVE_HIGH),
+		{ },
+	},
+};
+
 /**
  * struct clk_hifiberry_hw - Common struct to the HiFiBerry DAC Pro
+ * @dev: device
  * @hw: clk_hw for the common clk framework
  * @mode: 0 => CLK44EN, 1 => CLK48EN
  * @sclk_lookup: handle for "sclk"
+ * @gpio_44: gpiod desc for 44.1kHz support
+ * @gpio_48: gpiod desc for 48 kHz support
+ * @prepared: boolean caching clock state
+ * @gpio_initialized: boolean flag used to take gpio references.
  */
 struct clk_hifiberry_hw {
+	struct device *dev;
 	struct clk_hw hw;
 	u8 mode;
 	struct clk_lookup *sclk_lookup;
+	struct gpio_desc *gpio_44;
+	struct gpio_desc *gpio_48;
+	bool prepared;
+	bool gpio_initialized;
 };
 
 #define to_hifiberry_clk(_hw) container_of(_hw, struct clk_hifiberry_hw, hw)
@@ -69,6 +90,88 @@ static long clk_hifiberry_dacpro_round_rate(struct clk_hw *hw,
 	return actual_rate;
 }
 
+static int clk_hifiberry_dacpro_is_prepared(struct clk_hw *hw)
+{
+	struct clk_hifiberry_hw *clk = to_hifiberry_clk(hw);
+
+	return clk->prepared;
+}
+
+static int clk_hifiberry_dacpro_prepare(struct clk_hw *hw)
+{
+	struct clk_hifiberry_hw *clk = to_hifiberry_clk(hw);
+
+	/*
+	 * The gpios are handled here to avoid any dependencies on
+	 * probe.
+	 *
+	 * The user of the clock should verify with the PCM512
+	 * registers that the clock are actually present and stable.
+	 * This driver only toggles the relevant GPIOs.
+	 */
+	if (!clk->gpio_initialized) {
+
+		clk->gpio_44 = devm_gpiod_get(clk->dev,
+					      "PCM512x-GPIO6",
+					      GPIOD_OUT_LOW);
+		if (IS_ERR(clk->gpio_44)) {
+			dev_err(clk->dev, "gpio44 not found\n");
+			return PTR_ERR(clk->gpio_44);
+		}
+
+		clk->gpio_48 = devm_gpiod_get(clk->dev,
+					      "PCM512x-GPIO3",
+					      GPIOD_OUT_LOW);
+		if (IS_ERR(clk->gpio_48)) {
+			dev_err(clk->dev, "gpio48 not found\n");
+			return PTR_ERR(clk->gpio_48);
+		}
+
+		clk->gpio_initialized = true;
+	}
+
+	if (clk->prepared)
+		return 0;
+
+	switch (clk->mode) {
+	case 0:
+		/* 44.1 kHz */
+		gpiod_set_value(clk->gpio_44, 1);
+		break;
+	case 1:
+		/* 48 kHz */
+		gpiod_set_value(clk->gpio_48, 1);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	clk->prepared = 1;
+
+	return 0;
+}
+
+static void clk_hifiberry_dacpro_unprepare(struct clk_hw *hw)
+{
+	struct clk_hifiberry_hw *clk = to_hifiberry_clk(hw);
+
+	if (!clk->prepared)
+		return;
+
+	switch (clk->mode) {
+	case 0:
+		gpiod_set_value(clk->gpio_44, 0);
+		break;
+	case 1:
+		gpiod_set_value(clk->gpio_48, 0);
+		break;
+	default:
+		return;
+	}
+
+	clk->prepared = false;
+}
+
 static int clk_hifiberry_dacpro_set_rate(struct clk_hw *hw,
 					 unsigned long rate,
 					 unsigned long parent_rate)
@@ -83,6 +186,9 @@ static int clk_hifiberry_dacpro_set_rate(struct clk_hw *hw,
 }
 
 static const struct clk_ops clk_hifiberry_dacpro_rate_ops = {
+	.is_prepared = clk_hifiberry_dacpro_is_prepared,
+	.prepare = clk_hifiberry_dacpro_prepare,
+	.unprepare = clk_hifiberry_dacpro_unprepare,
 	.recalc_rate = clk_hifiberry_dacpro_recalc_rate,
 	.round_rate = clk_hifiberry_dacpro_round_rate,
 	.set_rate = clk_hifiberry_dacpro_set_rate,
@@ -97,6 +203,9 @@ static int clk_hifiberry_dacpro_probe(struct platform_device *pdev)
 
 	dev = &pdev->dev;
 
+	pcm512x_gpios_table.dev_id = dev_name(dev);
+	gpiod_add_lookup_table(&pcm512x_gpios_table);
+
 	proclk = devm_kzalloc(dev, sizeof(*proclk), GFP_KERNEL);
 	if (!proclk)
 		return -ENOMEM;
@@ -107,6 +216,7 @@ static int clk_hifiberry_dacpro_probe(struct platform_device *pdev)
 	init.parent_names = NULL;
 	init.num_parents = 0;
 
+	proclk->dev = dev;
 	proclk->mode = 0;
 	proclk->hw.init = &init;
 
-- 
2.20.1