[PATCH v3 1/4] w1: ds1wm: fix and simplify register access

[Johannes Poehlmann]

o Replace incorrect register offsett calculation by
direct configuration of bus_shift in mfd-cell.
Indirect definition of address-shift by resource size
was unobvious and should have used a binary log.
o Make endian clean, make HW-endianness configurable.
o Use ioread*, iowrite* instead of __raw_readb,__raw_writeb
to also use memory-barriers when accessing HW-registers.
We do not want reordering to happen here.

Signed-off-by: Johannes Poehlmann <johannes.poehlmann@xxxxxxxxxxx>
Acked-by: Evgeniy Polyakov <zbr@xxxxxxxxxxx>
---
 drivers/w1/masters/ds1wm.c | 84 ++++++++++++++++++++++++++++++++++++++++++----
 include/linux/mfd/ds1wm.h  |  9 +++++
 2 files changed, 87 insertions(+), 6 deletions(-)

diff --git a/drivers/w1/masters/ds1wm.c b/drivers/w1/masters/ds1wm.c
index fd2e9da..6bba2fe 100644
--- a/drivers/w1/masters/ds1wm.c
+++ b/drivers/w1/masters/ds1wm.c
@@ -95,7 +95,8 @@ static struct {
 
 struct ds1wm_data {
 	void     __iomem *map;
-	int      bus_shift; /* # of shifts to calc register offsets */
+	unsigned int      bus_shift; /* # of shifts to calc register offsets */
+	int      is_hw_big_endian;
 	struct platform_device *pdev;
 	const struct mfd_cell   *cell;
 	int      irq;
@@ -115,12 +116,66 @@ struct ds1wm_data {
 static inline void ds1wm_write_register(struct ds1wm_data *ds1wm_data, u32 reg,
 					u8 val)
 {
-	__raw_writeb(val, ds1wm_data->map + (reg << ds1wm_data->bus_shift));
+	if (ds1wm_data->is_hw_big_endian) {
+		switch (ds1wm_data->bus_shift) {
+		case 0:
+			iowrite8(val, ds1wm_data->map + (reg << 0));
+			break;
+		case 1:
+			iowrite16be((u16)val, ds1wm_data->map+(reg<<1));
+			break;
+		case 2:
+			iowrite32be((u32)val, ds1wm_data->map+(reg<<2));
+			break;
+		}
+	} else {
+		switch (ds1wm_data->bus_shift) {
+		case 0:
+			iowrite8(val, ds1wm_data->map + (reg << 0));
+			break;
+		case 1:
+			iowrite16((u16) val, ds1wm_data->map+(reg << 1));
+			break;
+		case 2:
+			iowrite32((u32) val, ds1wm_data->map+(reg << 2));
+			break;
+		}
+	}
 }
 
 static inline u8 ds1wm_read_register(struct ds1wm_data *ds1wm_data, u32 reg)
 {
-	return __raw_readb(ds1wm_data->map + (reg << ds1wm_data->bus_shift));
+
+	u32 val = 0;
+
+	if (ds1wm_data->is_hw_big_endian) {
+		switch (ds1wm_data->bus_shift) {
+		case 0:
+			val = ioread8(ds1wm_data->map + (reg << 0));
+			break;
+		case 1:
+			val = ioread16be(ds1wm_data->map + (reg << 1));
+			break;
+		case 2:
+			val = ioread32be(ds1wm_data->map + (reg << 2));
+			break;
+		}
+	} else {
+		switch (ds1wm_data->bus_shift) {
+		case 0:
+			val = ioread8(ds1wm_data->map + (reg << 0));
+			break;
+		case 1:
+			val = ioread16(ds1wm_data->map + (reg << 1));
+			break;
+		case 2:
+			val = ioread32(ds1wm_data->map + (reg << 2));
+			break;
+		}
+	}
+	dev_dbg(&ds1wm_data->pdev->dev,
+		"ds1wm_read_register reg: %d, 32 bit val:%x\n", reg, val);
+	return (u8) val;
 }
 
 
@@ -473,9 +528,6 @@ static int ds1wm_probe(struct platform_device *pdev)
 	if (!ds1wm_data->map)
 		return -ENOMEM;
 
-	/* calculate bus shift from mem resource */
-	ds1wm_data->bus_shift = resource_size(res) >> 3;
-
 	ds1wm_data->pdev = pdev;
 	ds1wm_data->cell = mfd_get_cell(pdev);
 	if (!ds1wm_data->cell)
@@ -484,6 +536,26 @@ static int ds1wm_probe(struct platform_device *pdev)
 	if (!plat)
 		return -ENODEV;
 
+	/* how many bits to shift register number to get register offset */
+	if (plat->bus_shift > 2) {
+		dev_err(&ds1wm_data->pdev->dev,
+			"illegal bus shift %d, not written",
+			ds1wm_data->bus_shift);
+		return -EINVAL;
+	}
+
+	ds1wm_data->bus_shift = plat->bus_shift;
+	/* make sure resource has space for 8 registers */
+	if ((8 << ds1wm_data->bus_shift) > resource_size(res)) {
+		dev_err(&ds1wm_data->pdev->dev,
+			"memory resource size %d to small, should be %d\n",
+			(int) resource_size(res),
+			8 << ds1wm_data->bus_shift);
+		return -EINVAL;
+	}
+
+	ds1wm_data->is_hw_big_endian = plat->is_hw_big_endian;
+
 	res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 	if (!res)
 		return -ENXIO;
diff --git a/include/linux/mfd/ds1wm.h b/include/linux/mfd/ds1wm.h
index 38a372a..4efd626 100644
--- a/include/linux/mfd/ds1wm.h
+++ b/include/linux/mfd/ds1wm.h
@@ -3,6 +3,7 @@
 struct ds1wm_driver_data {
 	int active_high;
 	int clock_rate;
+
 	/* in milliseconds, the amount of time to */
 	/* sleep following a reset pulse. Zero    */
 	/* should work if your bus devices recover*/
@@ -10,4 +11,12 @@ struct ds1wm_driver_data {
 	/* ds1wm implements the precise timings of*/
 	/* a reset pulse/presence detect sequence.*/
 	unsigned int reset_recover_delay;
+
+	/* Say 1 here for big endian Hardware */
+	/* (only relevant with bus-shift > 0 */
+	int is_hw_big_endian;
+
+	/* left shift of register number to get register address offsett */
+	/* only 0,1,2 allowed for 8,16 or 32 bit bus width respectively */
+	unsigned int bus_shift;
 };
-- 
2.1.4