drm/radeon/atom: fix bus probes when hw_i2c is set (v2)

When probing the bus, we need to set the byte count
to 0 rather than 1.

v2: Don't count the first byte.

bug:
https://bugzilla.kernel.org/show_bug.cgi?id=66241

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

1 files changed, 9 insertions, 6 deletions

diff --git a/drivers/gpu/drm/radeon/atombios_i2c.c b/drivers/gpu/drm/radeon/atombios_i2c.c
index 0652ee0a2098..f685035dbe39 100644
--- a/drivers/gpu/drm/radeon/atombios_i2c.c
+++ b/drivers/gpu/drm/radeon/atombios_i2c.c
@@ -44,7 +44,7 @@ static int radeon_process_i2c_ch(struct radeon_i2c_chan *chan,
         PROCESS_I2C_CHANNEL_TRANSACTION_PS_ALLOCATION args;
         int index = GetIndexIntoMasterTable(COMMAND, ProcessI2cChannelTransaction);
         unsigned char *base;
-        u16 out;
+        u16 out = cpu_to_le16(0);
 
         memset(&args, 0, sizeof(args));
 
@@ -55,11 +55,14 @@ static int radeon_process_i2c_ch(struct radeon_i2c_chan *chan,
                         DRM_ERROR("hw i2c: tried to write too many bytes (%d vs 3)\n", num);
                         return -EINVAL;
                 }
-                args.ucRegIndex = buf[0];
-                if (num > 1) {
+                if (buf == NULL)
+                        args.ucRegIndex = 0;
+                else
+                        args.ucRegIndex = buf[0];
+                if (num)
                         num--;
+                if (num)
                         memcpy(&out, &buf[1], num);
-                }
                 args.lpI2CDataOut = cpu_to_le16(out);
         } else {
                 if (num > ATOM_MAX_HW_I2C_READ) {
@@ -96,14 +99,14 @@ int radeon_atom_hw_i2c_xfer(struct i2c_adapter *i2c_adap,
         struct radeon_i2c_chan *i2c = i2c_get_adapdata(i2c_adap);
         struct i2c_msg *p;
         int i, remaining, current_count, buffer_offset, max_bytes, ret;
-        u8 buf = 0, flags;
+        u8 flags;
 
         /* check for bus probe */
         p = &msgs[0];
         if ((num == 1) && (p->len == 0)) {
                 ret = radeon_process_i2c_ch(i2c,
                                             p->addr, HW_I2C_WRITE,
-                                            &buf, 1);
+                                            NULL, 0);
                 if (ret)
                         return ret;
                 else