Re: [PATCH v7 3/8] media: qcom: camss: Prepare CSID for C-PHY support

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] CSID PHY selection state (`phy_sel`) is not reset when switching the link to the Test Pattern Generator (TPG), potentially leaving the hardware in C-PHY mode for TPG data.
--

commit 79ab3be6b44125cac8b0fb89e7dbad51a804a8bf
Author: David Heidelberg <david@ixit.cz>

media: qcom: camss: Prepare CSID for C-PHY support

This commit updates the CSID configuration to inherit C-PHY information
from CSIPHY, ensuring the CSI2_RX_CFG0_PHY_TYPE_SEL register is properly
set when C-PHY mode is used.

> diff --git a/drivers/media/platform/qcom/camss/camss-csid.c b/drivers/media/platform/qcom/camss/camss-csid.c
> index 48459b46a981b..bcc34ac9dd212 100644
> --- a/drivers/media/platform/qcom/camss/camss-csid.c
> +++ b/drivers/media/platform/qcom/camss/camss-csid.c
[ ... ]
> @@ -1291,6 +1291,11 @@ static int csid_link_setup(struct media_entity *entity,
>  
>  			lane_cfg = &csiphy->cfg.csi2->lane_cfg;
>  			csid->phy.lane_cnt = lane_cfg->num_data;
> +			if (lane_cfg->phy_cfg == V4L2_MBUS_CSI2_CPHY)
> +				csid->phy.phy_sel = CSID_PHY_SEL_CPHY;
> +			else
> +				csid->phy.phy_sel = CSID_PHY_SEL_DPHY;
> +

[Severity: Medium]
Does this leave the phy_sel state uninitialized when the link is switched
to the Test Pattern Generator (TPG)?

In csid_link_setup(), when switching the link to the internal TPG, the newly
added phy_sel field is not updated:

csid_link_setup() {
    ...
    if (sd->grp_id == TPG_GRP_ID) {
        tpg = v4l2_get_subdevdata(sd);

        csid->phy.lane_cnt = tpg->res->lane_cnt;
        csid->phy.csiphy_id = tpg->id;
        csid->phy.lane_assign = csid_get_lane_assign(NULL, csid->phy.lane_cnt);
        csid->tpg_linked = true;
        /* csid->phy.phy_sel is not reset here */
    } else {
    ...

If a C-PHY sensor was previously linked, phy_sel will retain the stale value
CSID_PHY_SEL_CPHY.

When streaming starts, __csid_configure_rx() writes this stale phy_sel value
into the CSI2_RX_CFG0_PHY_TYPE_SEL register, even for TPG streams.

Because the TPG bypasses the C-PHY 3-phase encoding, applying C-PHY decoding
rules to TPG data might cause the hardware to misinterpret the stream and
break the test pattern generator.

>  			csid->phy.lane_assign = csid_get_lane_assign(lane_cfg, lane_cfg->num_data);
>  			csid->tpg_linked = false;
>  		}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260605-qcom-cphy-v7-0-426c37e9008f@ixit.cz?part=3