* [PATCH v2 1/1] drm: xlnx: zynqmp: Use switch - case for link rate downshift
@ 2020-07-29 23:30 Hyun Kwon
2020-07-30 23:12 ` Laurent Pinchart
0 siblings, 1 reply; 4+ messages in thread
From: Hyun Kwon @ 2020-07-29 23:30 UTC (permalink / raw)
To: Laurent Pinchart, Daniel Vetter, dri-devel; +Cc: Hyun Kwon, Dan Carpenter
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;
--
2.7.4
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^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v2 1/1] drm: xlnx: zynqmp: Use switch - case for link rate downshift
2020-07-29 23:30 [PATCH v2 1/1] drm: xlnx: zynqmp: Use switch - case for link rate downshift Hyun Kwon
@ 2020-07-30 23:12 ` Laurent Pinchart
2020-07-31 2:33 ` Hyun Kwon
0 siblings, 1 reply; 4+ messages in thread
From: Laurent Pinchart @ 2020-07-30 23:12 UTC (permalink / raw)
To: Hyun Kwon; +Cc: Dan Carpenter, dri-devel, Daniel Vetter
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);
> 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
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dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2 1/1] drm: xlnx: zynqmp: Use switch - case for link rate downshift
2020-07-30 23:12 ` Laurent Pinchart
@ 2020-07-31 2:33 ` Hyun Kwon
2020-08-01 2:00 ` Hyun Kwon
0 siblings, 1 reply; 4+ messages in thread
From: Hyun Kwon @ 2020-07-31 2:33 UTC (permalink / raw)
To: Laurent Pinchart; +Cc: Dan Carpenter, dri-devel, Daniel Vetter
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);
> > 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
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https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 4+ messages in thread* RE: [PATCH v2 1/1] drm: xlnx: zynqmp: Use switch - case for link rate downshift
2020-07-31 2:33 ` Hyun Kwon
@ 2020-08-01 2:00 ` Hyun Kwon
0 siblings, 0 replies; 4+ messages in thread
From: Hyun Kwon @ 2020-08-01 2:00 UTC (permalink / raw)
To: Hyun Kwon, Laurent Pinchart; +Cc: dri-devel, Dan Carpenter
> -----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);
> > > 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@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
_______________________________________________
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^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-08-01 2:04 UTC | newest]
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2020-07-29 23:30 [PATCH v2 1/1] drm: xlnx: zynqmp: Use switch - case for link rate downshift Hyun Kwon
2020-07-30 23:12 ` Laurent Pinchart
2020-07-31 2:33 ` Hyun Kwon
2020-08-01 2:00 ` Hyun Kwon
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