Re: [PATCH v3 2/4] arm64: dts: sc7180: Specify "data-lanes" for DSI host output

Hi,

On Sun, Oct 31, 2021 at 7:52 PM Abhinav Kumar [off-list ref] wrote:

On 10/31/2021 2:01 PM, Abhinav Kumar wrote:

Hi Philip

On 10/29/2021 4:24 PM, Philip Chen wrote:

Hi Stephen,

On Fri, Oct 29, 2021 at 4:16 PM Stephen Boyd [off-list ref] wrote:

Quoting Philip Chen (2021-10-29 15:27:41)

MSM DSI host driver actually parses "data-lanes" in DT and compare
it with the number of DSI lanes the bridge driver sets for
mipi_dsi_device. So we need to always specify "data-lanes" for the
DSI host output. As of now, "data-lanes" is added to ti-sn65dsi86 dts
fragment, but missing in parade-ps8640 dts fragment, which requires
a fixup.

I don't see data-lanes required in the schema, and
dsi_host_parse_lane_data() seems happy to continue without it. I do see
that num_data_lanes isn't set though. Does this patch fix it?

The problem I see is from dsi_host_attach().
If there is no "data-lanes" in DT, num_data_lanes would be 0.
Then dsi_host_attach() would return -EINVAL.

Let me know if i am missing something here. the dsi_host_attach returns an error if

dsi->lanes is > than msm_host->num_data_lanes. That shouldnt happen even if

num_data_lanes will be 0

static int dsi_host_attach(struct mipi_dsi_host *host,
                    struct mipi_dsi_device *dsi)
{
    struct msm_dsi_host *msm_host = to_msm_dsi_host(host);
    int ret;

    if (dsi->lanes > msm_host->num_data_lanes)
        return -EINVAL;

Thanks

Abhinav

Please ignore this comment, I understood now. The fix you had posted to default to 4 lanes seems fine.

Will ack that one.

Thanks!
For the other folks: the fix I posted for dsi_host is here:
https://patchwork.kernel.org/project/linux-arm-msm/patch/20211030100812.1.I6cd9af36b723fed277d34539d3b2ba4ca233ad2d@changeid/