drm/radeon/kms: add support for external tmds on legacy boards

This enables initialization of external tmds chips on pre-atom
and mac systems.  Macs are untested.  Also, some macs have single
link tmds chips while others have dual link tmds chips.  We need
to figure out which ones have which.

This gets external TMDS working on my RS485 and RV380.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 56 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_i2c.c b/drivers/gpu/drm/radeon/radeon_i2c.c
index e97a3912d99f..6c645fb4dad8 100644
--- a/drivers/gpu/drm/radeon/radeon_i2c.c
+++ b/drivers/gpu/drm/radeon/radeon_i2c.c
@@ -212,3 +212,59 @@ struct drm_encoder *radeon_best_encoder(struct drm_connector *connector)
 {
         return NULL;
 }
+
+void radeon_i2c_sw_get_byte(struct radeon_i2c_chan *i2c_bus,
+                            u8 slave_addr,
+                            u8 addr,
+                            u8 *val)
+{
+        u8 out_buf[2];
+        u8 in_buf[2];
+        struct i2c_msg msgs[] = {
+                {
+                        .addr = slave_addr,
+                        .flags = 0,
+                        .len = 1,
+                        .buf = out_buf,
+                },
+                {
+                        .addr = slave_addr,
+                        .flags = I2C_M_RD,
+                        .len = 1,
+                        .buf = in_buf,
+                }
+        };
+
+        out_buf[0] = addr;
+        out_buf[1] = 0;
+
+        if (i2c_transfer(&i2c_bus->adapter, msgs, 2) == 2) {
+                *val = in_buf[0];
+                DRM_DEBUG("val = 0x%02x\n", *val);
+        } else {
+                DRM_ERROR("i2c 0x%02x 0x%02x read failed\n",
+                          addr, *val);
+        }
+}
+
+void radeon_i2c_sw_put_byte(struct radeon_i2c_chan *i2c_bus,
+                            u8 slave_addr,
+                            u8 addr,
+                            u8 val)
+{
+        uint8_t out_buf[2];
+        struct i2c_msg msg = {
+                .addr = slave_addr,
+                .flags = 0,
+                .len = 2,
+                .buf = out_buf,
+        };
+
+        out_buf[0] = addr;
+        out_buf[1] = val;
+
+        if (i2c_transfer(&i2c_bus->adapter, &msg, 1) != 1)
+                DRM_ERROR("i2c 0x%02x 0x%02x write failed\n",
+                          addr, val);
+}
+