patch "iio: dac: ad5593r: Fix i2c read protocol requirements" added to char-misc-testing

patch "iio: dac: ad5593r: Fix i2c read protocol requirements" added to char-misc-testing

[gregkh]

This is a note to let you know that I've just added the patch titled

    iio: dac: ad5593r: Fix i2c read protocol requirements

to my char-misc git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-testing branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will be merged to the char-misc-next branch sometime soon,
after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.


From 558a25f903b4af6361b7fbeea08a6446a0745653 Mon Sep 17 00:00:00 2001
From: Michael Hennerich <michael.hennerich@analog.com>
Date: Tue, 13 Sep 2022 09:34:12 +0200
Subject: iio: dac: ad5593r: Fix i2c read protocol requirements
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

For reliable operation across the full range of supported
interface rates, the AD5593R needs a STOP condition between
address write, and data read (like show in the datasheet Figure 40)
so in turn i2c_smbus_read_word_swapped cannot be used.

While at it, a simple helper was added to make the code simpler.

Fixes: 56ca9db862bf ("iio: dac: Add support for the AD5592R/AD5593R ADCs/DACs")
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220913073413.140475-2-nuno.sa@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/dac/ad5593r.c | 46 +++++++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/drivers/iio/dac/ad5593r.c b/drivers/iio/dac/ad5593r.c
index 34e1319a9712..356dc0bab115 100644
--- a/drivers/iio/dac/ad5593r.c
+++ b/drivers/iio/dac/ad5593r.c
@@ -13,6 +13,8 @@
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 
+#include <asm/unaligned.h>
+
 #define AD5593R_MODE_CONF		(0 << 4)
 #define AD5593R_MODE_DAC_WRITE		(1 << 4)
 #define AD5593R_MODE_ADC_READBACK	(4 << 4)
@@ -20,6 +22,24 @@
 #define AD5593R_MODE_GPIO_READBACK	(6 << 4)
 #define AD5593R_MODE_REG_READBACK	(7 << 4)
 
+static int ad5593r_read_word(struct i2c_client *i2c, u8 reg, u16 *value)
+{
+	int ret;
+	u8 buf[2];
+
+	ret = i2c_smbus_write_byte(i2c, reg);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_master_recv(i2c, buf, sizeof(buf));
+	if (ret < 0)
+		return ret;
+
+	*value = get_unaligned_be16(buf);
+
+	return 0;
+}
+
 static int ad5593r_write_dac(struct ad5592r_state *st, unsigned chan, u16 value)
 {
 	struct i2c_client *i2c = to_i2c_client(st->dev);
@@ -38,13 +58,7 @@ static int ad5593r_read_adc(struct ad5592r_state *st, unsigned chan, u16 *value)
 	if (val < 0)
 		return (int) val;
 
-	val = i2c_smbus_read_word_swapped(i2c, AD5593R_MODE_ADC_READBACK);
-	if (val < 0)
-		return (int) val;
-
-	*value = (u16) val;
-
-	return 0;
+	return ad5593r_read_word(i2c, AD5593R_MODE_ADC_READBACK, value);
 }
 
 static int ad5593r_reg_write(struct ad5592r_state *st, u8 reg, u16 value)
@@ -58,25 +72,19 @@ static int ad5593r_reg_write(struct ad5592r_state *st, u8 reg, u16 value)
 static int ad5593r_reg_read(struct ad5592r_state *st, u8 reg, u16 *value)
 {
 	struct i2c_client *i2c = to_i2c_client(st->dev);
-	s32 val;
-
-	val = i2c_smbus_read_word_swapped(i2c, AD5593R_MODE_REG_READBACK | reg);
-	if (val < 0)
-		return (int) val;
 
-	*value = (u16) val;
-
-	return 0;
+	return ad5593r_read_word(i2c, AD5593R_MODE_REG_READBACK | reg, value);
 }
 
 static int ad5593r_gpio_read(struct ad5592r_state *st, u8 *value)
 {
 	struct i2c_client *i2c = to_i2c_client(st->dev);
-	s32 val;
+	u16 val;
+	int ret;
 
-	val = i2c_smbus_read_word_swapped(i2c, AD5593R_MODE_GPIO_READBACK);
-	if (val < 0)
-		return (int) val;
+	ret = ad5593r_read_word(i2c, AD5593R_MODE_GPIO_READBACK, &val);
+	if (ret)
+		return ret;
 
 	*value = (u8) val;
 
-- 
2.37.3