[PATCH 5.19 019/717] iio: dac: ad5593r: Fix i2c read protocol requirements

Greg Kroah-Hartman
2022-10-22T07:35:27Z

From: Michael Hennerich <michael.hennerich@analog.com>

commit 558a25f903b4af6361b7fbeea08a6446a0745653 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iio/dac/ad5593r.c | 46 +++++++++++++++++++++++++++-------------------
1 file changed, 27 insertions(+), 19 deletions(-)

--- 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 ad559
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 ad55
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;