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@oracle.com Signed-off-by: Hyun Kwon hyun.kwon@xilinx.com --- 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;
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@oracle.com Signed-off-by: Hyun Kwon hyun.kwon@xilinx.com
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@ideasonboard.com
- 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);
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;
Hi Laurent,
Thanks for the comment.
On Thu, Jul 30, 2020 at 04:12:46PM -0700, Laurent Pinchart wrote:
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@oracle.com Signed-off-by: Hyun Kwon hyun.kwon@xilinx.com
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@ideasonboard.com
I agree. I'll fix and add the tag.
Thanks!
-hyun
- 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);
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
-----Original Message----- From: dri-devel dri-devel-bounces@lists.freedesktop.org On Behalf Of Hyun Kwon Sent: Thursday, July 30, 2020 7:33 PM To: Laurent Pinchart laurent.pinchart@ideasonboard.com Cc: Dan Carpenter dan.carpenter@oracle.com; dri- devel@lists.freedesktop.org; Daniel Vetter daniel.vetter@ffwll.ch.ch Subject: Re: [PATCH v2 1/1] drm: xlnx: zynqmp: Use switch - case for link rate downshift
Hi Laurent,
Thanks for the comment.
On Thu, Jul 30, 2020 at 04:12:46PM -0700, Laurent Pinchart wrote:
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@oracle.com Signed-off-by: Hyun Kwon hyun.kwon@xilinx.com
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@ideasonboard.com
I agree. I'll fix and add the tag.
Applied to drm-misc-next-fixes.
Thanks, -hyun
Thanks!
-hyun
- 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);
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
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Laurent Pinchart