ASoC: Add spi hw read function for 16 addr 8 data mode for ad193x fix

[This will be used by the ad193x driver to fix the fact that the
original author of the driver put a bodge for their particular chip into
a the generic ASoC register I/O abstraction layer which looked like an
obvious bug which ended up getting fixed in 3.0.  Sadly there were no
comments documenting what was going on.  A minimally invasive correction
to the driver is to remove the register cache support and go direct to
the hardware all the time so we're adding a new feature -- broonie]

Signed-off-by: Scott Jiang <scott.jiang.linux@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/sound/soc/soc-io.c b/sound/soc/soc-io.c
index cca490c80589..a62f7dd4ba96 100644
--- a/sound/soc/soc-io.c
+++ b/sound/soc/soc-io.c
@@ -205,6 +205,25 @@ static unsigned int snd_soc_16_8_read_i2c(struct snd_soc_codec *codec,
 #define snd_soc_16_8_read_i2c NULL
 #endif
 
+#if defined(CONFIG_SPI_MASTER)
+static unsigned int snd_soc_16_8_read_spi(struct snd_soc_codec *codec,
+                                          unsigned int r)
+{
+        struct spi_device *spi = codec->control_data;
+
+        const u16 reg = cpu_to_be16(r | 0x100);
+        u8 data;
+        int ret;
+
+        ret = spi_write_then_read(spi, &reg, 2, &data, 1);
+        if (ret < 0)
+                return 0;
+        return data;
+}
+#else
+#define snd_soc_16_8_read_spi NULL
+#endif
+
 static int snd_soc_16_8_write(struct snd_soc_codec *codec, unsigned int reg,
                               unsigned int value)
 {
@@ -295,6 +314,7 @@ static struct {
         int (*write)(struct snd_soc_codec *codec, unsigned int, unsigned int);
         unsigned int (*read)(struct snd_soc_codec *, unsigned int);
         unsigned int (*i2c_read)(struct snd_soc_codec *, unsigned int);
+        unsigned int (*spi_read)(struct snd_soc_codec *, unsigned int);
 } io_types[] = {
         {
                 .addr_bits = 4, .data_bits = 12,
@@ -318,6 +338,7 @@ static struct {
                 .addr_bits = 16, .data_bits = 8,
                 .write = snd_soc_16_8_write,
                 .i2c_read = snd_soc_16_8_read_i2c,
+                .spi_read = snd_soc_16_8_read_spi,
         },
         {
                 .addr_bits = 16, .data_bits = 16,
@@ -383,6 +404,8 @@ int snd_soc_codec_set_cache_io(struct snd_soc_codec *codec,
 #ifdef CONFIG_SPI_MASTER
                 codec->hw_write = do_spi_write;
 #endif
+                if (io_types[i].spi_read)
+                        codec->hw_read = io_types[i].spi_read;
 
                 codec->control_data = container_of(codec->dev,
                                                    struct spi_device,