Hi Hyun,
Thank you for the patch.
On Wed, Jul 29, 2020 at 04:30:45PM -0700, Hyun Kwon wrote:
> Use switch - case to downshift from the current link rate. It's a small
> loop now, so fine to be replaced with switch - case. With a loop, it is
> confusing and hard to follow as reported below.
>
> The patch d76271d22694: "drm: xlnx: DRM/KMS driver for Xilinx ZynqMP
> DisplayPort Subsystem" from Jul 7, 2018, leads to the following
> static checker warning:
>
> drivers/gpu/drm/xlnx/zynqmp_dp.c:594 zynqmp_dp_mode_configure()
> error: iterator underflow 'bws' (-1)-2
>
> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Signed-off-by: Hyun Kwon <hyun.kwon@xxxxxxxxxx>
> ---
> v2
> - Convert the for loop into switch - case
> ---
> ---
> drivers/gpu/drm/xlnx/zynqmp_dp.c | 29 ++++++++++++++++-------------
> 1 file changed, 16 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> index b735072..5d6adeaa 100644
> --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> @@ -567,34 +567,37 @@ static int zynqmp_dp_mode_configure(struct zynqmp_dp *dp, int pclock,
> u8 current_bw)
> {
> int max_rate = dp->link_config.max_rate;
> - u8 bws[3] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7, DP_LINK_BW_5_4 };
> + u8 bw_code;
> u8 max_lanes = dp->link_config.max_lanes;
> u8 max_link_rate_code = drm_dp_link_rate_to_bw_code(max_rate);
> u8 bpp = dp->config.bpp;
> u8 lane_cnt;
> - s8 i;
>
> - if (current_bw == DP_LINK_BW_1_62) {
> + /* Downshift from current one */
Maybe "Downshift from the current bandwidth" ?
Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> + switch (current_bw) {
> + case DP_LINK_BW_5_4:
> + bw_code = DP_LINK_BW_2_7;
> + break;
> + case DP_LINK_BW_2_7:
> + bw_code = DP_LINK_BW_1_62;
> + break;
> + case DP_LINK_BW_1_62:
> dev_err(dp->dev, "can't downshift. already lowest link rate\n");
> return -EINVAL;
> - }
> -
> - for (i = ARRAY_SIZE(bws) - 1; i >= 0; i--) {
> - if (current_bw && bws[i] >= current_bw)
> - continue;
> -
> - if (bws[i] <= max_link_rate_code)
> - break;
> + default:
> + /* If not given, start with max supported */
> + bw_code = max_link_rate_code;
> + break;
> }
>
> for (lane_cnt = 1; lane_cnt <= max_lanes; lane_cnt <<= 1) {
> int bw;
> u32 rate;
>
> - bw = drm_dp_bw_code_to_link_rate(bws[i]);
> + bw = drm_dp_bw_code_to_link_rate(bw_code);
> rate = zynqmp_dp_max_rate(bw, lane_cnt, bpp);
> if (pclock <= rate) {
> - dp->mode.bw_code = bws[i];
> + dp->mode.bw_code = bw_code;
> dp->mode.lane_cnt = lane_cnt;
> dp->mode.pclock = pclock;
> return dp->mode.bw_code;
--
Regards,
Laurent Pinchart
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
