iio:ad5791: Do not store transfer buffers on the stack

Some SPI controllers may not be able to handle transfer buffers that are placed
on the stack.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 21 insertions, 25 deletions

diff --git a/drivers/iio/dac/ad5791.c b/drivers/iio/dac/ad5791.c
index 1e7f4cd7db83..79bf19945747 100644
--- a/drivers/iio/dac/ad5791.c
+++ b/drivers/iio/dac/ad5791.c
@@ -91,6 +91,11 @@ struct ad5791_state {
         unsigned                        ctrl;
         unsigned                        pwr_down_mode;
         bool                            pwr_down;
+
+        union {
+                __be32 d32;
+                u8 d8[4];
+        } data[3] ____cacheline_aligned;
 };
 
 /**
@@ -104,48 +109,39 @@ enum ad5791_supported_device_ids {
         ID_AD5791,
 };
 
-static int ad5791_spi_write(struct spi_device *spi, u8 addr, u32 val)
+static int ad5791_spi_write(struct ad5791_state *st, u8 addr, u32 val)
 {
-        union {
-                __be32 d32;
-                u8 d8[4];
-        } data;
-
-        data.d32 = cpu_to_be32(AD5791_CMD_WRITE |
+        st->data[0].d32 = cpu_to_be32(AD5791_CMD_WRITE |
                               AD5791_ADDR(addr) |
                               (val & AD5791_DAC_MASK));
 
-        return spi_write(spi, &data.d8[1], 3);
+        return spi_write(st->spi, &st->data[0].d8[1], 3);
 }
 
-static int ad5791_spi_read(struct spi_device *spi, u8 addr, u32 *val)
+static int ad5791_spi_read(struct ad5791_state *st, u8 addr, u32 *val)
 {
-        union {
-                __be32 d32;
-                u8 d8[4];
-        } data[3];
         int ret;
         struct spi_transfer xfers[] = {
                 {
-                        .tx_buf = &data[0].d8[1],
+                        .tx_buf = &st->data[0].d8[1],
                         .bits_per_word = 8,
                         .len = 3,
                         .cs_change = 1,
                 }, {
-                        .tx_buf = &data[1].d8[1],
-                        .rx_buf = &data[2].d8[1],
+                        .tx_buf = &st->data[1].d8[1],
+                        .rx_buf = &st->data[2].d8[1],
                         .bits_per_word = 8,
                         .len = 3,
                 },
         };
 
-        data[0].d32 = cpu_to_be32(AD5791_CMD_READ |
+        st->data[0].d32 = cpu_to_be32(AD5791_CMD_READ |
                               AD5791_ADDR(addr));
-        data[1].d32 = cpu_to_be32(AD5791_ADDR(AD5791_ADDR_NOOP));
+        st->data[1].d32 = cpu_to_be32(AD5791_ADDR(AD5791_ADDR_NOOP));
 
-        ret = spi_sync_transfer(spi, xfers, ARRAY_SIZE(xfers));
+        ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
 
-        *val = be32_to_cpu(data[2].d32);
+        *val = be32_to_cpu(st->data[2].d32);
 
         return ret;
 }
@@ -210,7 +206,7 @@ static ssize_t ad5791_write_dac_powerdown(struct iio_dev *indio_dev,
         }
         st->pwr_down = pwr_down;
 
-        ret = ad5791_spi_write(st->spi, AD5791_ADDR_CTRL, st->ctrl);
+        ret = ad5791_spi_write(st, AD5791_ADDR_CTRL, st->ctrl);
 
         return ret ? ret : len;
 }
@@ -263,7 +259,7 @@ static int ad5791_read_raw(struct iio_dev *indio_dev,
 
         switch (m) {
         case IIO_CHAN_INFO_RAW:
-                ret = ad5791_spi_read(st->spi, chan->address, val);
+                ret = ad5791_spi_read(st, chan->address, val);
                 if (ret)
                         return ret;
                 *val &= AD5791_DAC_MASK;
@@ -330,7 +326,7 @@ static int ad5791_write_raw(struct iio_dev *indio_dev,
                 val &= AD5791_RES_MASK(chan->scan_type.realbits);
                 val <<= chan->scan_type.shift;
 
-                return ad5791_spi_write(st->spi, chan->address, val);
+                return ad5791_spi_write(st, chan->address, val);
 
         default:
                 return -EINVAL;
@@ -393,7 +389,7 @@ static int ad5791_probe(struct spi_device *spi)
                 dev_warn(&spi->dev, "reference voltage unspecified\n");
         }
 
-        ret = ad5791_spi_write(spi, AD5791_ADDR_SW_CTRL, AD5791_SWCTRL_RESET);
+        ret = ad5791_spi_write(st, AD5791_ADDR_SW_CTRL, AD5791_SWCTRL_RESET);
         if (ret)
                 goto error_disable_reg_neg;
 
@@ -405,7 +401,7 @@ static int ad5791_probe(struct spi_device *spi)
                   | ((pdata && pdata->use_rbuf_gain2) ? 0 : AD5791_CTRL_RBUF) |
                   AD5791_CTRL_BIN2SC;
 
-        ret = ad5791_spi_write(spi, AD5791_ADDR_CTRL, st->ctrl |
+        ret = ad5791_spi_write(st, AD5791_ADDR_CTRL, st->ctrl |
                 AD5791_CTRL_OPGND | AD5791_CTRL_DACTRI);
         if (ret)
                 goto error_disable_reg_neg;