linux-kernel - [PATCH v4 2/5] w1: ds1wm: make endian clean and use standard io memory accessors

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Date:   Tue, 25 Jul 2017 13:27:12 +0200
From:   Johannes Poehlmann <johannes.poehlmann@...-labs.de>
To:     linux-kernel@...r.kernel.org
Cc:     Johannes Poehlmann <johannes.poehlmann@...-labs.de>,
        Evgeniy Polyakov <zbr@...emap.net>,
        Greg Kroah-Hartman <greg@...ah.com>
Subject: [PATCH v4 2/5] w1: ds1wm: make endian clean and use standard io memory accessors

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.

Both changes are tightly coupled, so I do them in one patch

Signed-off-by: Johannes Poehlmann <johannes.poehlmann@...-labs.de>
Acked-by: Evgeniy Polyakov <zbr@...emap.net>
---
 drivers/w1/masters/ds1wm.c | 60 ++++++++++++++++++++++++++++++++++++++++++++--
 include/linux/mfd/ds1wm.h  |  5 ++++
 2 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/drivers/w1/masters/ds1wm.c b/drivers/w1/masters/ds1wm.c
index 401e53e..d15575d 100644
--- a/drivers/w1/masters/ds1wm.c
+++ b/drivers/w1/masters/ds1wm.c
@@ -96,6 +96,7 @@ static struct {
 struct ds1wm_data {
 	void     __iomem *map;
 	unsigned int      bus_shift; /* # of shifts to calc register offsets */
+	bool      is_hw_big_endian;
 	struct platform_device *pdev;
 	const struct mfd_cell   *cell;
 	int      irq;
@@ -115,12 +116,65 @@ 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;
 }
 
 
@@ -499,6 +553,8 @@ static int ds1wm_probe(struct platform_device *pdev)
 		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 79a01e8..2227c6a 100644
--- a/include/linux/mfd/ds1wm.h
+++ b/include/linux/mfd/ds1wm.h
@@ -16,6 +16,11 @@ struct ds1wm_driver_data {
 	 */
 	unsigned int reset_recover_delay;
 
+	/* Say 1 here for big endian Hardware
+	 * (only relevant with bus-shift > 0
+	 */
+	bool 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
 	 */
-- 
2.1.4