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.
v2: switch to WARN_ON_ONCE
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
---
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..8d74de8 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_ONCE(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].
*/
--
1.8.3.1
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