drm/amdgpu: The I2C IP doesn't support 0 writes/reads
authorLuben Tuikov <luben.tuikov@amd.com>
Fri, 2 Jul 2021 23:58:42 +0000 (19:58 -0400)
committerAlex Deucher <alexander.deucher@amd.com>
Thu, 8 Jul 2021 19:12:51 +0000 (15:12 -0400)
commitc0838d3a93fc5e51b4a9654f53f499da1778dad8
treec768cb17e118cf6651a08e19bd75e515e83acd77
parentae87df077554347e89d39a7383e74547401c7f5d
drm/amdgpu: The I2C IP doesn't support 0 writes/reads

The I2C IP doesn't support writes or reads of 0 bytes.

In order for a START/STOP transaction to take
place on the bus, the data written/read has to be
at least one byte.

That is, you cannot generate a write with 0 bytes,
just to get the ACK from a device, just so you can
probe that device if it is on the bus and so to
discover all devices on the bus--you'll have to
read at least one byte. Writes of 0 bytes generate
no START/STOP on this I2C IP--the bus is not
engaged at all.

Set the I2C_AQ_NO_ZERO_LEN to the existing I2C
quirk tables for Aldebaran, Arcturus, Navi10 and
Sienna Cichlid, and add a quirk table to the I2C
driver which drives the bus when the SMU
doesn't--for instance on Vega20.

Cc: Alexander Deucher <Alexander.Deucher@amd.com>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Cc: Lijo Lazar <Lijo.Lazar@amd.com>
Cc: John Clements <john.clements@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Lijo Lazar <Lijo.Lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drivers/gpu/drm/amd/amdgpu/smu_v11_0_i2c.c
drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c
drivers/gpu/drm/amd/pm/swsmu/smu11/navi10_ppt.c
drivers/gpu/drm/amd/pm/swsmu/smu11/sienna_cichlid_ppt.c
drivers/gpu/drm/amd/pm/swsmu/smu13/aldebaran_ppt.c