On Fri, Sep 19, 2025 at 10:24:31PM +0800, Xiangxu Yin wrote:
> QCS615 platform requires non-default logical-to-physical lane mapping due
> to its unique hardware routing. Unlike the standard mapping sequence
> <0 1 2 3>, QCS615 uses <3 2 0 1>, which necessitates explicit
> configuration via the data-lanes property in the device tree. This ensures
> correct signal routing between the DP controller and PHY.
>
> For partial definitions, fill remaining lanes with unused physical lanes
> in ascending order.
>
> Signed-off-by: Xiangxu Yin <xiangxu....@oss.qualcomm.com>
> ---
> drivers/gpu/drm/msm/dp/dp_ctrl.c | 10 +++----
> drivers/gpu/drm/msm/dp/dp_link.c | 60
> ++++++++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/msm/dp/dp_link.h | 1 +
> 3 files changed, 66 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_link.c
> b/drivers/gpu/drm/msm/dp/dp_link.c
> index
> 2aeb3ecf76fab2ee6a9512b785ca5dceebfc3964..34a91e194a124ef5372f13352f7b3513aa88da2a
> 100644
> --- a/drivers/gpu/drm/msm/dp/dp_link.c
> +++ b/drivers/gpu/drm/msm/dp/dp_link.c
> @@ -1236,6 +1236,61 @@ static u32 msm_dp_link_link_frequencies(struct
> device_node *of_node)
> return frequency;
> }
>
> +/*
> + * Always populate msm_dp_link->lane_map with 4 lanes.
> + * - Use DTS "data-lanes" if present; otherwise fall back to default mapping.
> + * - For partial definitions, fill remaining entries with unused lanes in
> + * ascending order.
> + */
> +static int msm_dp_link_lane_map(struct device *dev, struct msm_dp_link
> *msm_dp_link)
> +{
> + struct device_node *of_node = dev->of_node;
> + struct device_node *endpoint;
> + int cnt = msm_dp_link->max_dp_lanes;
> + u32 tmp[DP_MAX_NUM_DP_LANES];
> + u32 map[DP_MAX_NUM_DP_LANES] = {0, 1, 2, 3}; /* default 1:1 mapping */
> + bool used[DP_MAX_NUM_DP_LANES] = {false};
> + int i, j = 0, ret = -EINVAL;
> +
> + endpoint = of_graph_get_endpoint_by_regs(of_node, 1, -1);
> + if (endpoint) {
> + ret = of_property_read_u32_array(endpoint, "data-lanes", tmp,
> cnt);
> + if (ret)
> + dev_dbg(dev, "endpoint data-lanes read failed
> (ret=%d)\n", ret);
> + }
> +
> + if (ret) {
> + ret = of_property_read_u32_array(of_node, "data-lanes", tmp,
> cnt);
> + if (ret) {
> + dev_info(dev, "data-lanes not defined, set to
> default\n");
> + goto out;
> + }
> + }
> +
> + for (i = 0; i < cnt; i++) {
> + if (tmp[i] >= DP_MAX_NUM_DP_LANES) {
> + dev_err(dev, "data-lanes[%d]=%u out of range\n", i,
> tmp[i]);
> + return -EINVAL;
> + }
> + used[tmp[i]] = true;
> + map[i] = tmp[i];
> + }
> +
> + /* Fill the remaining entries with unused physical lanes (ascending) */
> + for (i = cnt; i < DP_MAX_NUM_DP_LANES && j < DP_MAX_NUM_DP_LANES; j++) {
Nit: i = cnt, j = 0; Don't init loop variables at the top of the
function.
Other than that:
Reviewed-by: Dmitry Baryshkov <dmitry.barysh...@oss.qualcomm.com>
> + if (!used[j])
> + map[i++] = j;
> + }
> +
> +out:
> + if (endpoint)
> + of_node_put(endpoint);
> +
> + dev_dbg(dev, "data-lanes count %d <%d %d %d %d>\n", cnt, map[0],
> map[1], map[2], map[3]);
> + memcpy(msm_dp_link->lane_map, map, sizeof(map));
> + return 0;
> +}
> +
> static int msm_dp_link_parse_dt(struct device *dev, struct msm_dp_link
> *msm_dp_link)
> {
> struct device_node *of_node = dev->of_node;
--
With best wishes
Dmitry
