drm/amdgpu: The I2C IP doesn't support 0 writes/reads

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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>

...

This commit is contained in:

Luben Tuikov 2021-07-02 19:58:42 -04:00 • committed by Alex Deucher

parent ae87df0775

commit c0838d3a93

5 changed files with 9 additions and 4 deletions

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5

drivers/gpu/drm/amd/amdgpu/smu_v11_0_i2c.c

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2

drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c

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2

drivers/gpu/drm/amd/pm/swsmu/smu11/navi10_ppt.c

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2

drivers/gpu/drm/amd/pm/swsmu/smu11/sienna_cichlid_ppt.c

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2

drivers/gpu/drm/amd/pm/swsmu/smu13/aldebaran_ppt.c

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