ARM: bcm2835: add stub clock driver

This patch adds a minimal stub clock driver for the BCM2835. Its sole
purpose is to allow the PL011 AMBA clk_get() API calls to provide
something that looks enough like a clock that the driver probes and
operates correctly.

This patch was extracted from git://github.com/lp0/linux.git branch
rpi-split as of 2012/09/08, and modified as follows:

* Reworked to call clk_register_fixed_rate(), and clk_register_clkdev()
rather than using static data to represent the clocks.
* Moved implementation to drivers/clk/.
* Modified .dev_id for UART clocks to match UART DT node names.
* s/bcm2708/bcm2835/.
* Modified device tree vendor prefix.

Signed-off-by: Chris Boot <[e-mail]>
Signed-off-by: Simon Arlott <[e-mail]>
Signed-off-by: Dom Cobley <[e-mail]>
Signed-off-by: Dom Cobley <[e-mail]>
Signed-off-by: Stephen Warren <[e-mail]>
Acked-by: Mike Turquette <[e-mail]>

arch/arm/mach-bcm2835/bcm2835.c

···
 #include <linux/irqchip/bcm2835.h>
 #include <linux/of_platform.h>
 #include <linux/bcm2835_timer.h>
+#include <linux/clk/bcm2835.h>
 
 #include <asm/mach/arch.h>
 #include <asm/mach/map.h>
···
 void __init bcm2835_init(void)
 {
 	int ret;
+
+	bcm2835_init_clocks();
 
 	ret = of_platform_populate(NULL, of_default_bus_match_table, NULL,
 				   NULL);

drivers/clk/Makefile

···
 obj-$(CONFIG_COMMON_CLK)	+= clk.o clk-fixed-rate.o clk-gate.o \
 				   clk-mux.o clk-divider.o clk-fixed-factor.o
 # SoCs specific
+obj-$(CONFIG_ARCH_BCM2835)	+= clk-bcm2835.o
 obj-$(CONFIG_ARCH_NOMADIK)	+= clk-nomadik.o
 obj-$(CONFIG_ARCH_HIGHBANK)	+= clk-highbank.o
 obj-$(CONFIG_ARCH_MXS)		+= mxs/

drivers/clk/clk-bcm2835.c

···
+/*
+ * Copyright (C) 2010 Broadcom
+ * Copyright (C) 2012 Stephen Warren
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/clkdev.h>
+#include <linux/clk/bcm2835.h>
+
+/*
+ * These are fixed clocks. They're probably not all root clocks and it may
+ * be possible to turn them on and off but until this is mapped out better
+ * it's the only way they can be used.
+ */
+void __init bcm2835_init_clocks(void)
+{
+	struct clk *clk;
+	int ret;
+
+	clk = clk_register_fixed_rate(NULL, "sys_pclk", NULL, CLK_IS_ROOT,
+					250000000);
+	if (!clk)
+		pr_err("sys_pclk not registered\n");
+
+	clk = clk_register_fixed_rate(NULL, "apb_pclk", NULL, CLK_IS_ROOT,
+					126000000);
+	if (!clk)
+		pr_err("apb_pclk not registered\n");
+
+	clk = clk_register_fixed_rate(NULL, "uart0_pclk", NULL, CLK_IS_ROOT,
+					3000000);
+	if (!clk)
+		pr_err("uart0_pclk not registered\n");
+	ret = clk_register_clkdev(clk, NULL, "20201000.uart");
+	if (ret)
+		pr_err("uart0_pclk alias not registered\n");
+
+	clk = clk_register_fixed_rate(NULL, "uart1_pclk", NULL, CLK_IS_ROOT,
+					125000000);
+	if (!clk)
+		pr_err("uart1_pclk not registered\n");
+	ret = clk_register_clkdev(clk, NULL, "20215000.uart");
+	if (ret)
+		pr_err("uart0_pclk alias not registered\n");
+}

include/linux/clk/bcm2835.h

···
+/*
+ * Copyright (C) 2010 Broadcom
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef __LINUX_CLK_BCM2835_H_
+#define __LINUX_CLK_BCM2835_H_
+
+void __init bcm2835_init_clocks(void);
+
+#endif