Re: [PATCH] drm/komeda: Fix off-by-1 when with readback conn due to rounding
On 3/12/21 10:55 AM, Brian Starkey wrote: (Adding back James again - did you use get_maintainer.pl?) On Thu, Mar 11, 2021 at 12:08:46PM +, carsten.haitz...@foss.arm.com wrote: From: Carsten Haitzler When setting up a readback connector that writes data back to memory rather than to an actual output device (HDMI etc.), rounding was set to round. As the DPU uses a higher internal number of bits when generating a color value, this round-down back to 8bit ended up with everything being off-by one. e.g. #fefefe became #ff. This sets Perhaps overly pedantic, but now we've tracked down what was actually happening I think we can be more precise here. Not _everything_ is off-by-one, it's just rounding in the standard sense - if the most Well a very large number of pixels were off-by-1 ... I guess it's an exaggeration but a "vast number of pixels were off by 1". I guess I was just using common terms like "everything is expensive here" doesn't actually mean absolutely everything but a very vast number of things. You know what I mean. :) The comment as a whole describing rounding policies should provide more details. I just write the log as a "when spelunking through history, this log will give me some broader insight into what this change is without being war and peace and If I want to see more and this commit is interesting to my spelunking efforts, I'll git log -U to read that". significant bit-to-be-discarded is set, the value is rounded up to minimise the absolute error introduced by bit-depth reduction. rounding to "round-down" so things end up correct by turning on the LW_TRC round down flag. Can we call it "truncate" rather than round down? I think it makes "TRC" a bit more understandable. That's the official name from the docs though (TRC)... makes it easier to match to them... So I think you can argue this both ways. The comment where it's used though does make it clear... Signed-off-by: Carsten Haitzler --- drivers/gpu/drm/arm/display/komeda/d71/d71_component.c | 7 ++- drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h | 1 + 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c index 8a02ade369db..e97acc5519d1 100644 --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c @@ -468,7 +468,12 @@ static void d71_wb_layer_update(struct komeda_component *c, struct komeda_layer_state *st = to_layer_st(state); struct drm_connector_state *conn_st = state->wb_conn->state; struct komeda_fb *kfb = to_kfb(conn_st->writeback_job->fb); - u32 ctrl = L_EN | LW_OFM, mask = L_EN | LW_OFM | LW_TBU_EN; + /* LW_TRC sets rounding to truncate not round which is needed for +* the output of writeback to match the input in the most common +* use cases like RGB888 -> RGB888, so set this bit by default +*/ Hm, not sure why this file uses "net/" style comments, but as you said, this is in-keeping with the rest of the file, so meh :-) Yup. Just stick to "follow the style there" unless there is seemingly a good reason that what is there is horribly "broken" and needs fixing up. + u32 ctrl = LW_TRC | L_EN | LW_OFM; + u32 mask = LW_TRC | L_EN | LW_OFM | LW_TBU_EN; If you were aiming for matching register order, this should be: L_EN | LW_TRC | LW_OFM | LW_TBU_EN I think it'd be nice to have the exact behaviour in the commit message, but either way this seems OK as a pragmatic fix so: git log -U ? :) Reviewed-by: Brian Starkey Thanks, -Brian u32 __iomem *reg = c->reg; d71_layer_update_fb(c, kfb, st->addr); diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h index e80172a0b320..a8036689d721 100644 --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h @@ -321,6 +321,7 @@ #define LAYER_WR_FORMAT 0x0D8 /* Layer_WR control bits */ +#define LW_TRC BIT(1) #define LW_OFMBIT(4) #define LW_LALPHA(x) (((x) & 0xFF) << 8) #define LW_A_WCACHE(x)(((x) & 0xF) << 28) -- 2.30.0 ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm/komeda: Fix off-by-1 when with readback conn due to rounding
On Fri, Mar 12, 2021 at 10:55:21AM +, Brian Starkey wrote: > (Adding back James again - did you use get_maintainer.pl?) > > On Thu, Mar 11, 2021 at 12:08:46PM +, carsten.haitz...@foss.arm.com wrote: > > From: Carsten Haitzler > > > > When setting up a readback connector that writes data back to memory > > rather than to an actual output device (HDMI etc.), rounding was set > > to round. As the DPU uses a higher internal number of bits when generating > > a color value, this round-down back to 8bit ended up with everything > > being off-by one. e.g. #fefefe became #ff. This sets > > Perhaps overly pedantic, but now we've tracked down what was actually > happening I think we can be more precise here. Not _everything_ is > off-by-one, it's just rounding in the standard sense - if the most > significant bit-to-be-discarded is set, the value is rounded up to > minimise the absolute error introduced by bit-depth reduction. > > > rounding to "round-down" so things end up correct by turning on the LW_TRC > > round down flag. > > Can we call it "truncate" rather than round down? I think it makes > "TRC" a bit more understandable. > > > > > Signed-off-by: Carsten Haitzler > > --- > > drivers/gpu/drm/arm/display/komeda/d71/d71_component.c | 7 ++- > > drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h | 1 + > > 2 files changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > > b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > > index 8a02ade369db..e97acc5519d1 100644 > > --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > > +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > > @@ -468,7 +468,12 @@ static void d71_wb_layer_update(struct > > komeda_component *c, > > struct komeda_layer_state *st = to_layer_st(state); > > struct drm_connector_state *conn_st = state->wb_conn->state; > > struct komeda_fb *kfb = to_kfb(conn_st->writeback_job->fb); > > - u32 ctrl = L_EN | LW_OFM, mask = L_EN | LW_OFM | LW_TBU_EN; > > + /* LW_TRC sets rounding to truncate not round which is needed for > > +* the output of writeback to match the input in the most common > > +* use cases like RGB888 -> RGB888, so set this bit by default > > +*/ > > Hm, not sure why this file uses "net/" style comments, but as you > said, this is in-keeping with the rest of the file, so meh :-) > > > + u32 ctrl = LW_TRC | L_EN | LW_OFM; > > + u32 mask = LW_TRC | L_EN | LW_OFM | LW_TBU_EN; > > If you were aiming for matching register order, this should be: > > L_EN | LW_TRC | LW_OFM | LW_TBU_EN > > > I think it'd be nice to have the exact behaviour in the commit > message, but either way this seems OK as a pragmatic fix so: > > Reviewed-by: Brian Starkey > > Thanks, > -Brian > > > u32 __iomem *reg = c->reg; > > > > d71_layer_update_fb(c, kfb, st->addr); > > diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > > b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > > index e80172a0b320..a8036689d721 100644 > > --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > > +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > > @@ -321,6 +321,7 @@ > > #define LAYER_WR_FORMAT0x0D8 > > > > /* Layer_WR control bits */ > > +#define LW_TRC BIT(1) > > #define LW_OFM BIT(4) > > #define LW_LALPHA(x) (((x) & 0xFF) << 8) > > #define LW_A_WCACHE(x) (((x) & 0xF) << 28) > > -- > > 2.30.0 > > Acked-by: James Qian Wang Thanks James > > ___ > > dri-devel mailing list > > dri-devel@lists.freedesktop.org > > https://lists.freedesktop.org/mailman/listinfo/dri-devel ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm/komeda: Fix off-by-1 when with readback conn due to rounding
(Adding back James again - did you use get_maintainer.pl?) On Thu, Mar 11, 2021 at 12:08:46PM +, carsten.haitz...@foss.arm.com wrote: > From: Carsten Haitzler > > When setting up a readback connector that writes data back to memory > rather than to an actual output device (HDMI etc.), rounding was set > to round. As the DPU uses a higher internal number of bits when generating > a color value, this round-down back to 8bit ended up with everything > being off-by one. e.g. #fefefe became #ff. This sets Perhaps overly pedantic, but now we've tracked down what was actually happening I think we can be more precise here. Not _everything_ is off-by-one, it's just rounding in the standard sense - if the most significant bit-to-be-discarded is set, the value is rounded up to minimise the absolute error introduced by bit-depth reduction. > rounding to "round-down" so things end up correct by turning on the LW_TRC > round down flag. Can we call it "truncate" rather than round down? I think it makes "TRC" a bit more understandable. > > Signed-off-by: Carsten Haitzler > --- > drivers/gpu/drm/arm/display/komeda/d71/d71_component.c | 7 ++- > drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h | 1 + > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > index 8a02ade369db..e97acc5519d1 100644 > --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > @@ -468,7 +468,12 @@ static void d71_wb_layer_update(struct komeda_component > *c, > struct komeda_layer_state *st = to_layer_st(state); > struct drm_connector_state *conn_st = state->wb_conn->state; > struct komeda_fb *kfb = to_kfb(conn_st->writeback_job->fb); > - u32 ctrl = L_EN | LW_OFM, mask = L_EN | LW_OFM | LW_TBU_EN; > + /* LW_TRC sets rounding to truncate not round which is needed for > + * the output of writeback to match the input in the most common > + * use cases like RGB888 -> RGB888, so set this bit by default > + */ Hm, not sure why this file uses "net/" style comments, but as you said, this is in-keeping with the rest of the file, so meh :-) > + u32 ctrl = LW_TRC | L_EN | LW_OFM; > + u32 mask = LW_TRC | L_EN | LW_OFM | LW_TBU_EN; If you were aiming for matching register order, this should be: L_EN | LW_TRC | LW_OFM | LW_TBU_EN I think it'd be nice to have the exact behaviour in the commit message, but either way this seems OK as a pragmatic fix so: Reviewed-by: Brian Starkey Thanks, -Brian > u32 __iomem *reg = c->reg; > > d71_layer_update_fb(c, kfb, st->addr); > diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > index e80172a0b320..a8036689d721 100644 > --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > @@ -321,6 +321,7 @@ > #define LAYER_WR_FORMAT 0x0D8 > > /* Layer_WR control bits */ > +#define LW_TRC BIT(1) > #define LW_OFM BIT(4) > #define LW_LALPHA(x) (((x) & 0xFF) << 8) > #define LW_A_WCACHE(x) (((x) & 0xF) << 28) > -- > 2.30.0 > > ___ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
[PATCH] drm/komeda: Fix off-by-1 when with readback conn due to rounding
From: Carsten Haitzler When setting up a readback connector that writes data back to memory rather than to an actual output device (HDMI etc.), rounding was set to round. As the DPU uses a higher internal number of bits when generating a color value, this round-down back to 8bit ended up with everything being off-by one. e.g. #fefefe became #ff. This sets rounding to "round-down" so things end up correct by turning on the LW_TRC round down flag. Signed-off-by: Carsten Haitzler --- drivers/gpu/drm/arm/display/komeda/d71/d71_component.c | 7 ++- drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h | 1 + 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c index 8a02ade369db..e97acc5519d1 100644 --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c @@ -468,7 +468,12 @@ static void d71_wb_layer_update(struct komeda_component *c, struct komeda_layer_state *st = to_layer_st(state); struct drm_connector_state *conn_st = state->wb_conn->state; struct komeda_fb *kfb = to_kfb(conn_st->writeback_job->fb); - u32 ctrl = L_EN | LW_OFM, mask = L_EN | LW_OFM | LW_TBU_EN; + /* LW_TRC sets rounding to truncate not round which is needed for +* the output of writeback to match the input in the most common +* use cases like RGB888 -> RGB888, so set this bit by default +*/ + u32 ctrl = LW_TRC | L_EN | LW_OFM; + u32 mask = LW_TRC | L_EN | LW_OFM | LW_TBU_EN; u32 __iomem *reg = c->reg; d71_layer_update_fb(c, kfb, st->addr); diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h index e80172a0b320..a8036689d721 100644 --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h @@ -321,6 +321,7 @@ #define LAYER_WR_FORMAT0x0D8 /* Layer_WR control bits */ +#define LW_TRC BIT(1) #define LW_OFM BIT(4) #define LW_LALPHA(x) (((x) & 0xFF) << 8) #define LW_A_WCACHE(x) (((x) & 0xF) << 28) -- 2.30.0 ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm/komeda: Fix off-by-1 when with readback conn due to rounding
On 3/9/21 11:36 AM, Brian Starkey wrote: Hi Carsten, (+James for komeda) Thanks for typing this up. On Fri, Mar 05, 2021 at 04:38:53PM +, carsten.haitz...@foss.arm.com wrote: From: Carsten Haitzler When setting up a readback conenctor that writes data back to memory s/readback conenctor/writeback connector/ (similar in the subject) rather than to an actual output device (HDMI etc.), rounding was ses s/ses/set/ I swear I re-read the log text... I must be auto-correcting in my head as I read. :) to round-down. As the DPU uses a higher internal number of bits when "round-down" isn't really accurate - the rounding mode "rounds" based on the most-significant discarded bit - so can round-up too. Come to think of it, I can't explain 0xff becoming 0xfe, but still, truncation is likely fine. Actually it was the other way - I mixed up the src/dest, but TRC does fix it which is the important bit. generating a color value, this round-down back to 8bit ended up with everything being off-by one. e.g. #ff became #fefefe. This sets rounding to "round" so things end up correct by turning on the round flag (LW_TRC). LW_TRC is the truncation flag. 0: Round, 1: Truncate Signed-off-by: Carsten Haitzler --- drivers/gpu/drm/arm/display/komeda/d71/d71_component.c | 6 +- drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h | 1 + 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c index 8a02ade369db..d551e79fa0f1 100644 --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c @@ -468,7 +468,11 @@ static void d71_wb_layer_update(struct komeda_component *c, struct komeda_layer_state *st = to_layer_st(state); struct drm_connector_state *conn_st = state->wb_conn->state; struct komeda_fb *kfb = to_kfb(conn_st->writeback_job->fb); - u32 ctrl = L_EN | LW_OFM, mask = L_EN | LW_OFM | LW_TBU_EN; + /* LW_TRC sets rounding to round not truncate which is needed for + * the output of writeback to match the input in the most common + * use cases like RGB888 -> RGB888, so set this bit by default */ /* * Comment style should be like this */ Same as above though - your description is inverted. By setting the LW_TRC bit, you're forcing the hardware to truncate instead of round. Yeah - inverted. But the source does have mixed comment styles with some /* * */ and some /* */ and some /* */ with the last 2 most common. + u32 ctrl = L_EN | LW_OFM | LW_TRC; + u32 mask = L_EN | LW_OFM | LW_TBU_EN | LW_TRC; Really nitpicking, but I think it'd be good to keep these in the same order as the bits in the register: L_EN | LW_TRC | LW_OFM | LW_TBU_EN I can do that. I'll send another with the above. Cheers, -Brian u32 __iomem *reg = c->reg; d71_layer_update_fb(c, kfb, st->addr); diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h index e80172a0b320..a8036689d721 100644 --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h @@ -321,6 +321,7 @@ #define LAYER_WR_FORMAT 0x0D8 /* Layer_WR control bits */ +#define LW_TRC BIT(1) #define LW_OFMBIT(4) #define LW_LALPHA(x) (((x) & 0xFF) << 8) #define LW_A_WCACHE(x)(((x) & 0xF) << 28) -- 2.30.0 ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Re: [PATCH] drm/komeda: Fix off-by-1 when with readback conn due to rounding
Hi Carsten, (+James for komeda) Thanks for typing this up. On Fri, Mar 05, 2021 at 04:38:53PM +, carsten.haitz...@foss.arm.com wrote: > From: Carsten Haitzler > > When setting up a readback conenctor that writes data back to memory s/readback conenctor/writeback connector/ (similar in the subject) > rather than to an actual output device (HDMI etc.), rounding was ses s/ses/set/ > to round-down. As the DPU uses a higher internal number of bits when "round-down" isn't really accurate - the rounding mode "rounds" based on the most-significant discarded bit - so can round-up too. Come to think of it, I can't explain 0xff becoming 0xfe, but still, truncation is likely fine. > generating a color value, this round-down back to 8bit ended up with > everything being off-by one. e.g. #ff became #fefefe. This sets > rounding to "round" so things end up correct by turning on the round > flag (LW_TRC). LW_TRC is the truncation flag. 0: Round, 1: Truncate > > Signed-off-by: Carsten Haitzler > --- > drivers/gpu/drm/arm/display/komeda/d71/d71_component.c | 6 +- > drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h | 1 + > 2 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > index 8a02ade369db..d551e79fa0f1 100644 > --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c > @@ -468,7 +468,11 @@ static void d71_wb_layer_update(struct komeda_component > *c, > struct komeda_layer_state *st = to_layer_st(state); > struct drm_connector_state *conn_st = state->wb_conn->state; > struct komeda_fb *kfb = to_kfb(conn_st->writeback_job->fb); > - u32 ctrl = L_EN | LW_OFM, mask = L_EN | LW_OFM | LW_TBU_EN; > + /* LW_TRC sets rounding to round not truncate which is needed for > + * the output of writeback to match the input in the most common > + * use cases like RGB888 -> RGB888, so set this bit by default */ /* * Comment style should be like this */ Same as above though - your description is inverted. By setting the LW_TRC bit, you're forcing the hardware to truncate instead of round. > + u32 ctrl = L_EN | LW_OFM | LW_TRC; > + u32 mask = L_EN | LW_OFM | LW_TBU_EN | LW_TRC; Really nitpicking, but I think it'd be good to keep these in the same order as the bits in the register: L_EN | LW_TRC | LW_OFM | LW_TBU_EN Cheers, -Brian > u32 __iomem *reg = c->reg; > > d71_layer_update_fb(c, kfb, st->addr); > diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > index e80172a0b320..a8036689d721 100644 > --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h > @@ -321,6 +321,7 @@ > #define LAYER_WR_FORMAT 0x0D8 > > /* Layer_WR control bits */ > +#define LW_TRC BIT(1) > #define LW_OFM BIT(4) > #define LW_LALPHA(x) (((x) & 0xFF) << 8) > #define LW_A_WCACHE(x) (((x) & 0xF) << 28) > -- > 2.30.0 > > ___ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
[PATCH] drm/komeda: Fix off-by-1 when with readback conn due to rounding
From: Carsten Haitzler When setting up a readback conenctor that writes data back to memory rather than to an actual output device (HDMI etc.), rounding was ses to round-down. As the DPU uses a higher internal number of bits when generating a color value, this round-down back to 8bit ended up with everything being off-by one. e.g. #ff became #fefefe. This sets rounding to "round" so things end up correct by turning on the round flag (LW_TRC). Signed-off-by: Carsten Haitzler --- drivers/gpu/drm/arm/display/komeda/d71/d71_component.c | 6 +- drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h | 1 + 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c index 8a02ade369db..d551e79fa0f1 100644 --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_component.c @@ -468,7 +468,11 @@ static void d71_wb_layer_update(struct komeda_component *c, struct komeda_layer_state *st = to_layer_st(state); struct drm_connector_state *conn_st = state->wb_conn->state; struct komeda_fb *kfb = to_kfb(conn_st->writeback_job->fb); - u32 ctrl = L_EN | LW_OFM, mask = L_EN | LW_OFM | LW_TBU_EN; + /* LW_TRC sets rounding to round not truncate which is needed for + * the output of writeback to match the input in the most common + * use cases like RGB888 -> RGB888, so set this bit by default */ + u32 ctrl = L_EN | LW_OFM | LW_TRC; + u32 mask = L_EN | LW_OFM | LW_TBU_EN | LW_TRC; u32 __iomem *reg = c->reg; d71_layer_update_fb(c, kfb, st->addr); diff --git a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h index e80172a0b320..a8036689d721 100644 --- a/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h +++ b/drivers/gpu/drm/arm/display/komeda/d71/d71_regs.h @@ -321,6 +321,7 @@ #define LAYER_WR_FORMAT0x0D8 /* Layer_WR control bits */ +#define LW_TRC BIT(1) #define LW_OFM BIT(4) #define LW_LALPHA(x) (((x) & 0xFF) << 8) #define LW_A_WCACHE(x) (((x) & 0xF) << 28) -- 2.30.0 ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
