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>

diff --git a/drivers/iio/dac/ad5791.c b/drivers/iio/dac/ad5791.c
index 1e7f4cd..79bf199 100644 (file)
--- 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;