On 9/23/2025 7:39 AM, Dmitry Baryshkov wrote: > On Mon, Sep 22, 2025 at 08:13:00AM -0700, Rob Clark wrote: >> On Fri, Sep 19, 2025 at 11:35 AM Dmitry Baryshkov >> <[email protected]> wrote: >>> 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 <[email protected]> >>>> --- >>>> 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. >> These days we can party like it's c99 and declare loop variables >> inside the for(), instead of at the top of the function. My >> preference is to do so, unless the loop variable is used after the >> loop. > Ack, works for me too. I think I'm not used for having theese parts of > C99 allowed in the kernel.
Got it. j is only used in that for loop, so I'll update it to use C99-style declaration as suggested.
