[PATCH v2 2/2] clk: fsl-sai: new driver

[Michael Walle]

With this driver it is possible to use the BCLK pin of the SAI module as
a generic clock output. This is esp. useful if you want to drive a clock
to an audio codec. Because the output only allows integer divider values
the audio codec needs an integrated PLL.

Signed-off-by: Michael Walle <michael@xxxxxxxx>
---
changes since v1:
 - none

 drivers/clk/Kconfig       | 12 ++++++
 drivers/clk/Makefile      |  1 +
 drivers/clk/clk-fsl-sai.c | 84 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 97 insertions(+)
 create mode 100644 drivers/clk/clk-fsl-sai.c

diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 45653a0e6ecd..dd1a5abc4ce8 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -174,6 +174,18 @@ config COMMON_CLK_CS2000_CP
 	help
 	  If you say yes here you get support for the CS2000 clock multiplier.
 
+config COMMON_CLK_FSL_SAI
+	bool "Clock driver for BCLK of Freescale SAI cores"
+	depends on ARCH_LAYERSCAPE || COMPILE_TEST
+	help
+	  This driver supports the Freescale SAI (Synchronous Audio Interface)
+	  to be used as a generic clock output. Some SoCs have restrictions
+	  regarding the possible pin multiplexer settings. Eg. on some SoCs
+	  two SAI interfaces can only be enabled together. If just one is
+	  needed, the BCLK pin of the second one can be used as general
+	  purpose clock output. Ideally, it can be used to drive an audio
+	  codec (sometimes known as MCLK).
+
 config COMMON_CLK_GEMINI
 	bool "Clock driver for Cortina Systems Gemini SoC"
 	depends on ARCH_GEMINI || COMPILE_TEST
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 0696a0c1ab58..ec23fd956228 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_ARCH_CLPS711X)		+= clk-clps711x.o
 obj-$(CONFIG_COMMON_CLK_CS2000_CP)	+= clk-cs2000-cp.o
 obj-$(CONFIG_ARCH_EFM32)		+= clk-efm32gg.o
 obj-$(CONFIG_COMMON_CLK_FIXED_MMIO)	+= clk-fixed-mmio.o
+obj-$(CONFIG_COMMON_CLK_FSL_SAI)	+= clk-fsl-sai.o
 obj-$(CONFIG_COMMON_CLK_GEMINI)		+= clk-gemini.o
 obj-$(CONFIG_COMMON_CLK_ASPEED)		+= clk-aspeed.o
 obj-$(CONFIG_MACH_ASPEED_G6)		+= clk-ast2600.o
diff --git a/drivers/clk/clk-fsl-sai.c b/drivers/clk/clk-fsl-sai.c
new file mode 100644
index 000000000000..b92054d15ab1
--- /dev/null
+++ b/drivers/clk/clk-fsl-sai.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Freescale SAI BCLK as a generic clock driver
+ *
+ * Copyright 2019 Kontron Europe GmbH
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/slab.h>
+
+#define I2S_CSR		0x00
+#define I2S_CR2		0x08
+#define CSR_BCE_BIT	28
+#define CR2_BCD		BIT(24)
+#define CR2_DIV_SHIFT	0
+#define CR2_DIV_WIDTH	8
+
+struct fsl_sai_clk {
+	struct clk_divider div;
+	struct clk_gate gate;
+	spinlock_t lock;
+};
+
+static void __init fsl_sai_clk_setup(struct device_node *node)
+{
+	const char *clk_name = node->name;
+	struct fsl_sai_clk *sai_clk;
+	unsigned int num_parents;
+	const char *parent_name;
+	void __iomem *base;
+	struct clk_hw *hw;
+
+	num_parents = of_clk_get_parent_count(node);
+	if (!num_parents) {
+		pr_err("%s: no parent found", clk_name);
+		return;
+	}
+
+	parent_name = of_clk_get_parent_name(node, 0);
+
+	sai_clk = kzalloc(sizeof(*sai_clk), GFP_KERNEL);
+	if (!sai_clk)
+		return;
+
+	base = of_iomap(node, 0);
+	if (base == NULL) {
+		pr_err("%s: failed to map register space", clk_name);
+		goto err;
+	}
+
+	spin_lock_init(&sai_clk->lock);
+
+	sai_clk->gate.reg = base + I2S_CSR;
+	sai_clk->gate.bit_idx = CSR_BCE_BIT;
+	sai_clk->gate.lock = &sai_clk->lock;
+
+	sai_clk->div.reg = base + I2S_CR2;
+	sai_clk->div.shift = CR2_DIV_SHIFT;
+	sai_clk->div.width = CR2_DIV_WIDTH;
+	sai_clk->div.lock = &sai_clk->lock;
+
+	/* set clock direction, we are the BCLK master */
+	writel(CR2_BCD, base + I2S_CR2);
+
+	hw = clk_hw_register_composite(NULL, clk_name, &parent_name, 1,
+				       NULL, NULL,
+				       &sai_clk->div.hw, &clk_divider_ops,
+				       &sai_clk->gate.hw, &clk_gate_ops,
+				       CLK_SET_RATE_GATE);
+	if (IS_ERR(hw))
+		goto err;
+
+	of_clk_add_hw_provider(node, of_clk_hw_simple_get, hw);
+
+	return;
+
+err:
+	kfree(sai_clk);
+}
+
+CLK_OF_DECLARE(fsl_sai_clk, "fsl,vf610-sai-clock", fsl_sai_clk_setup);
-- 
2.20.1