mfd: add basic Super I/O chip helpers

Super I/O chips are ICs common to x86 that are used for interfacing
to low-bandwidth peripherals. They often contain serial ports, watchdog
timers and hardware monitoring units.

They are usually addressable via one of two I/O port pairs, either
0x2e-0x2f or 0x4e-0x4f, but they don't typically respond to reads from
their range unless a device-specific 'password' has been poked in.
After this is done, they are read and written in the same manner however.

On Linux, these devices aren't subject to any device/driver model.
Each driver for some function (e.g. watchdog or GPIO) duplicates the
device probe in the module_init and board-specific configuration
is handled via module parameters.

Lets do it a bit fancier in barebox and add a helper to register chips
and a regmap for the control and configuration registers as well as a
helper to register child devices for each function contained within the
Super I/O chip.
Board-specific configuration, e.g. which pin to use as a watchdog reset,
can then be realized using barebox device-specific parameters.

The regmap will be more of a debugging aid, however.
For ease of porting from Linux, it's expected that access to the
I/O ports won't happen via the regmap. For this reason, the new
<superio.h> header offers functions to read/write these chips' registers
as well.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 64 insertions, 0 deletions

diff --git a/include/superio.h b/include/superio.h
new file mode 100644
index 0000000000..12bff58b6b
--- /dev/null
+++ b/include/superio.h
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Ahmad Fatoum, Pengutronix
+ */
+
+#ifndef _SUPERIO_H_
+#define _SUPERIO_H_
+
+#include <asm/io.h>
+#include <linux/bitops.h>
+#include <driver.h>
+#include <linux/types.h>
+
+#define SIO_REG_DEVID		0x20	/* Device ID (2 bytes) */
+#define SIO_REG_DEVREV		0x22	/* Device revision */
+#define SIO_REG_MANID		0x23	/* Vendor ID (2 bytes) */
+
+static inline u8 superio_inb(u16 base, u8 reg)
+{
+	outb(reg, base);
+	return inb(base + 1);
+}
+
+static inline u16 superio_inw(u16 base, u8 reg)
+{
+	u16 val;
+	val  = superio_inb(base, reg) << 8;
+	val |= superio_inb(base, reg + 1);
+	return val;
+}
+
+static inline void superio_outb(u16 base, u8 reg, u8 val)
+{
+	outb(reg, base);
+	outb(val, base + 1);
+}
+
+static inline void superio_set_bit(u16 base, u8 reg, unsigned bit)
+{
+	unsigned long val = superio_inb(base, reg);
+	__set_bit(bit, &val);
+	superio_outb(base, reg, val);
+}
+
+static inline void superio_clear_bit(u16 base, u8 reg, unsigned bit)
+{
+	unsigned long val = superio_inb(base, reg);
+	__clear_bit(bit, &val);
+	superio_outb(base, reg, val);
+}
+
+struct superio_chip {
+	struct device_d *dev;
+	u16 vid;
+	u16 devid;
+	u16 sioaddr;
+	void (*enter)(u16 sioaddr);
+	void (*exit)(u16 sioaddr);
+};
+
+void superio_chip_add(struct superio_chip *chip);
+struct device_d *superio_func_add(struct superio_chip *chip, const char *name);
+
+#endif