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 */
+ 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;
--
2.7.4
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