Re: [PATCH 0/8] media: qcom: camss: add V4L2 subdev streams API support

[Hitesh Patel]

Hi Gjorgji,

I tested this series on RB3 Gen2 (QCS6490 / SC7280) with two GMSL
cameras behind a MAX9296A deserializer, one camera per CSI-2 port, so
that the deserializer subdev heads two independent camss pipelines.
That is the case my own series [1] patches 6-8 tried to handle in
camss-video; with your series enabled on SC7280 they are not needed,
and I have dropped them from v2 of that series.

Results with streams_enable set on the SC7280 CSIPHY/CSID/VFE
resources (patch below):

- each camera alone, repeated start/stop: 5/5 and 5/5
- both cameras streaming at the same time: works
- the second camera started and stopped 8 times while the first one
  keeps streaming: 7/8, the first camera never disturbed. The one miss
  is a sensor/serializer settling issue we see on every kernel when
  the second camera is started within ~2 s of the first, unrelated to
  camss.
- CSID test pattern generator still works.

One problem found, fixed by the first patch below: with the streams
API a non-lite CSID registers 4 pads, but camss_link_entities() still
links CSID source pad MSM_CSID_PAD_FIRST_SRC + j to line j of every
VFE. On SC7280 the non-lite csid0 is linked to vfe_lite0, which has
four lines, so it asks for source pad 4 and the driver fails to probe:

  WARNING: drivers/media/mc/mc-entity.c:1150 media_create_pad_link
  qcom-camss acb3000.isp: Failed to link msm_csid0->msm_vfe3_rdi3 entities: -22

SM8250 does not see it because of csid_vfe_fixed_pairing. You may
prefer to fold the guard into patch 4, or keep all MSM_CSID_PADS_NUM
pads for the non-lite CSID; either works for me.

A note on the test tree: the series applies cleanly to next-20260911,
but our board runs the qualcomm-linux qcom-next branch (v7.2), whose
camss-csiphy.c has a legacy/generic-PHY ops split that yours does not
know about. I ported the CSIPHY part by hand there (a second
csiphy_streams_v4l2_ops carrying the legacy core ops, and the
enable/disable_streams helpers calling csiphy_set_stream_legacy() when
csiphy->phy is not available). Worth keeping in mind if this series
is meant to land in qcom-next as well.

The three VFE fixes in [1] (buffer done gating, write master
selection on 17x, VFE reset with another line streaming) are needed
on top of your series too for two RDI lines on one VFE; they are
independent and I have kept them in v2.

[1] https://lore.kernel.org/linux-media/20260914133416.1030231-1-hitesh@xxxxxxxxxxxxxx/

Tested-by: Hitesh Patel <hitesh@xxxxxxxxxxxxxx>

Hitesh Patel (2):
  media: qcom: camss: Do not link CSID source pads the CSID does not have
  media: qcom: camss: Enable the streams API on SC7280

(the two patches follow as replies to this mail)