lib: add support for stmp-style devices

MX23/28 use IP cores which follow a register layout I have first seen on
STMP3xxx SoCs. In this layout, every register actually has four u32:

1.) to store a value directly
2.) a SET register where every 1-bit sets the corresponding bit,
others are unaffected
3.) same with a CLR register
4.) same with a TOG (toggle) register

Also, the 2 MSBs in register 0 are always the same and can be used to reset
the IP core.

All this is strictly speaking not mach-specific (but IP core specific) and,
thus, doesn't need to be in mach-mxs/include. At least mx6 also uses IP cores
following this stmp-style. So:

Introduce a stmp-style device, put the code and defines for that in a public
place (lib/), and let drivers for stmp-style devices select that code.
To avoid regressions and ease reviewing, the actual code is simply copied from
mach-mxs. It definately wants updates, but those need a seperate patch series.

Voila, mach dependency gone, reusable code introduced. Note that I didn't
remove the duplicated code from mach-mxs yet, first the drivers have to be
converted.

Signed-off-by: Wolfram Sang <[e-mail]>
Acked-by: Shawn Guo <[e-mail]>
Acked-by: Dong Aisheng <[e-mail]>

include/linux/stmp_device.h

···
+/*
+ * basic functions for devices following the "stmp" style register layout
+ *
+ * Copyright (C) 2011 Wolfram Sang, Pengutronix e.K.
+ *
+ * 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.
+ */
+
+#ifndef __STMP_DEVICE_H__
+#define __STMP_DEVICE_H__
+
+#define STMP_OFFSET_REG_SET	0x4
+#define STMP_OFFSET_REG_CLR	0x8
+#define STMP_OFFSET_REG_TOG	0xc
+
+extern int stmp_reset_block(void __iomem *);
+#endif /* __STMP_DEVICE_H__ */

lib/Kconfig

···
 	boolean
 	default n
 
+config STMP_DEVICE
+	bool
+
 config CRC_CCITT
 	tristate "CRC-CCITT functions"
 	help

lib/Makefile

···
 
 obj-$(CONFIG_CLZ_TAB) += clz_tab.o
 
+obj-$(CONFIG_STMP_DEVICE) += stmp_device.o
+
 hostprogs-y	:= gen_crc32table
 clean-files	:= crc32table.h
 

lib/stmp_device.c

···
+/*
+ * Copyright (C) 1999 ARM Limited
+ * Copyright (C) 2000 Deep Blue Solutions Ltd
+ * Copyright 2006-2007,2010 Freescale Semiconductor, Inc. All Rights Reserved.
+ * Copyright 2008 Juergen Beisert, [e-mail]
+ * Copyright 2009 Ilya Yanok, Emcraft Systems Ltd, [e-mail]
+ * Copyright (C) 2011 Wolfram Sang, Pengutronix e.K.
+ *
+ * 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.
+ */
+
+#include <linux/io.h>
+#include <linux/errno.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/stmp_device.h>
+
+#define STMP_MODULE_CLKGATE	(1 << 30)
+#define STMP_MODULE_SFTRST	(1 << 31)
+
+/*
+ * Clear the bit and poll it cleared.  This is usually called with
+ * a reset address and mask being either SFTRST(bit 31) or CLKGATE
+ * (bit 30).
+ */
+static int stmp_clear_poll_bit(void __iomem *addr, u32 mask)
+{
+	int timeout = 0x400;
+
+	writel(mask, addr + STMP_OFFSET_REG_CLR);
+	udelay(1);
+	while ((readl(addr) & mask) && --timeout)
+		/* nothing */;
+
+	return !timeout;
+}
+
+int stmp_reset_block(void __iomem *reset_addr)
+{
+	int ret;
+	int timeout = 0x400;
+
+	/* clear and poll SFTRST */
+	ret = stmp_clear_poll_bit(reset_addr, STMP_MODULE_SFTRST);
+	if (unlikely(ret))
+		goto error;
+
+	/* clear CLKGATE */
+	writel(STMP_MODULE_CLKGATE, reset_addr + STMP_OFFSET_REG_CLR);
+
+	/* set SFTRST to reset the block */
+	writel(STMP_MODULE_SFTRST, reset_addr + STMP_OFFSET_REG_SET);
+	udelay(1);
+
+	/* poll CLKGATE becoming set */
+	while ((!(readl(reset_addr) & STMP_MODULE_CLKGATE)) && --timeout)
+		/* nothing */;
+	if (unlikely(!timeout))
+		goto error;
+
+	/* clear and poll SFTRST */
+	ret = stmp_clear_poll_bit(reset_addr, STMP_MODULE_SFTRST);
+	if (unlikely(ret))
+		goto error;
+
+	/* clear and poll CLKGATE */
+	ret = stmp_clear_poll_bit(reset_addr, STMP_MODULE_CLKGATE);
+	if (unlikely(ret))
+		goto error;
+
+	return 0;
+
+error:
+	pr_err("%s(%p): module reset timeout\n", __func__, reset_addr);
+	return -ETIMEDOUT;
+}
+EXPORT_SYMBOL(stmp_reset_block);