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Date: Wed, 19 Nov 2014 23:15:42 +0000
From: James Hogan <james.hogan@...tec.com>
To: Mike Turquette <mturquette@...aro.org>,
linux-metag@...r.kernel.org, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org
Cc: James Hogan <james.hogan@...tec.com>
Subject: [PATCH 14/15] clk: tz1090: add divider clock driver
Add driver for TZ1090 clock divider, which divides an input clock by an
integer.
Two policy decisions are made depending on the MMIO address of the
divider:
- The UART clock divider sets CLK_SET_RATE_PARENT so that clock changes
can propagate up to the CLK_UART_SW mux which allows more precision to
be achieved.
- The Meta clock divider sets CLK_DIVIDER_READ_ONLY to prevent it being
changed dynamically. This is normally set by the bootloader along with
the system PLL and has a whole bunch of derivative peripheral clocks.
Signed-off-by: James Hogan <james.hogan@...tec.com>
Cc: Mike Turquette <mturquette@...aro.org>
Cc: linux-metag@...r.kernel.org
---
drivers/clk/tz1090/Makefile | 1 +
drivers/clk/tz1090/clk-tz1090-divider.c | 96 +++++++++++++++++++++++++++++++++
2 files changed, 97 insertions(+)
create mode 100644 drivers/clk/tz1090/clk-tz1090-divider.c
diff --git a/drivers/clk/tz1090/Makefile b/drivers/clk/tz1090/Makefile
index 92e38a8..529c79c 100644
--- a/drivers/clk/tz1090/Makefile
+++ b/drivers/clk/tz1090/Makefile
@@ -1,5 +1,6 @@
# Makefile for TZ1090-specific clocks
obj-y += clk-tz1090-deleter.o
+obj-y += clk-tz1090-divider.o
obj-y += clk-tz1090-gate-bank.o
obj-y += clk-tz1090-mux-bank.o
obj-y += clk-tz1090-pdc.o
diff --git a/drivers/clk/tz1090/clk-tz1090-divider.c b/drivers/clk/tz1090/clk-tz1090-divider.c
new file mode 100644
index 0000000..92788f1
--- /dev/null
+++ b/drivers/clk/tz1090/clk-tz1090-divider.c
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2011 Sascha Hauer, Pengutronix <s.hauer@...gutronix.de>
+ * Copyright (C) 2011 Richard Zhao, Linaro <richard.zhao@...aro.org>
+ * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette@...aro.org>
+ * Copyright (C) 2014 Imagination Technologies Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Basic clock divider in TZ1090 SoC.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+
+#define CR_TOP_UARTCLK_DIV 0x02005928
+#define CR_TOP_META_CLKDIV 0x02005918
+
+/**
+ * tz1090_divider_policy() - Apply policy based on the specific divider.
+ * @res: MMIO resource.
+ * @flags: Clock flags to be modified depending on the divider.
+ * @divider_flags: Divider flags to be modified depending on the divider.
+ */
+static void tz1090_divider_policy(const struct resource *res,
+ unsigned long *flags, u8 *divider_flags)
+{
+ switch (res->start) {
+ case CR_TOP_UARTCLK_DIV:
+ /*
+ * UART clock changes must propagate up to CLK_UART_SW, which
+ * muxes between XTAL1 and sys_clk_undeleted, in order to get
+ * enough precision.
+ */
+ *flags |= CLK_SET_RATE_PARENT;
+ break;
+ case CR_TOP_META_CLKDIV:
+ /*
+ * The output of this divider is sys_clk_undeleted. It is set up
+ * by the bootloader along with the system PLL, and has a whole
+ * bunch of derivative peripheral clocks. It would be a really
+ * bad idea to allow it to change on the fly.
+ */
+ *divider_flags |= CLK_DIVIDER_READ_ONLY;
+ break;
+ }
+}
+
+/**
+ * tz1090_divider_clk_setup() - Setup function for TZ1090 divider clock.
+ * @node: DT node.
+ */
+static void tz1090_divider_clk_setup(struct device_node *node)
+{
+ struct clk *clk;
+ const char *clk_name = node->name;
+ void __iomem *reg;
+ const char *parent_name;
+ unsigned long flags = 0;
+ u8 divider_flags = 0;
+ u32 mask = 0;
+ u32 shift = 0;
+ struct resource res;
+
+ of_property_read_string(node, "clock-output-names", &clk_name);
+
+ parent_name = of_clk_get_parent_name(node, 0);
+
+ reg = of_iomap(node, 0);
+ if (!reg) {
+ pr_err("%s: no memory mapped for property reg\n", __func__);
+ return;
+ }
+
+ if (of_property_read_u32(node, "bit-mask", &mask)) {
+ pr_err("%s: missing bit-mask property for %s\n",
+ __func__, node->name);
+ return;
+ }
+
+ /* Apply policy decisions depending on which divider this is */
+ if (of_address_to_resource(node, 0, &res))
+ return;
+ tz1090_divider_policy(&res, &flags, ÷r_flags);
+
+ clk = clk_register_divider_mask(NULL, clk_name, parent_name, flags, reg,
+ shift, mask, divider_flags, NULL, NULL);
+
+ if (!IS_ERR(clk))
+ of_clk_add_provider(node, of_clk_src_simple_get, clk);
+}
+CLK_OF_DECLARE(divider_clk, "img,tz1090-divider", tz1090_divider_clk_setup);
--
2.0.4
--
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