On 21.02.2015 01:56, Alex Deucher wrote:

The atom aux param interface only supports 4 bits for the total write transfer size (header + payload). This limits us to 12 bytes of payload rather than 16. Add a check for this. Reads are not affected.

Signed-off-by: Alex Deucher alexander.deucher@amd.com

drivers/gpu/drm/radeon/atombios_dp.c | 7 +++++++ 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/radeon/atombios_dp.c b/drivers/gpu/drm/radeon/atombios_dp.c index 5bf825d..c57706e6 100644 --- a/drivers/gpu/drm/radeon/atombios_dp.c +++ b/drivers/gpu/drm/radeon/atombios_dp.c @@ -178,6 +178,13 @@ radeon_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) switch (msg->request & ~DP_AUX_I2C_MOT) { case DP_AUX_NATIVE_WRITE: case DP_AUX_I2C_WRITE:

• /* The atom implementation only supports writes with a max payload of
  

•  * 12 bytes since it uses 4 bits for the total count (header + payload)
  

•  * in the parameter space.  The atom interface supports 16 byte
  

•  * payloads for reads. The hw itself supports up to 16 bytes of payload.
  

•  */
  

• if (WARN_ON(msg->size > 12))
  

• 	return -E2BIG;
  

  /* tx_size needs to be 4 even for bare address packets since the atom
  • table needs the info in tx_buf[3].
  */

Might be safer to use WARN_ON_ONCE to avoid spamming dmesg if the warning ever gets triggered.