Re: [PATCH 4/4] drm/atomic-helper: Add select_output_bus_format callback
Hi,
On Wed, Feb 28, 2024 at 10:00:19PM +, Klymenko, Anatoliy wrote:
> > > diff --git a/include/drm/drm_modeset_helper_vtables.h
> > > b/include/drm/drm_modeset_helper_vtables.h
> > > index 881b03e4dc28..7c21ae1fe3ad 100644
> > > --- a/include/drm/drm_modeset_helper_vtables.h
> > > +++ b/include/drm/drm_modeset_helper_vtables.h
> > > @@ -489,6 +489,37 @@ struct drm_crtc_helper_funcs {
> > >bool in_vblank_irq, int *vpos, int *hpos,
> > >ktime_t *stime, ktime_t *etime,
> > >const struct drm_display_mode *mode);
> > > +
> > > + /**
> > > + * @select_output_bus_format
> > > + *
> > > + * Called by the first connected DRM bridge to negotiate input media
> > > + * bus format. CRTC is expected to pick preferable media formats from
> > > + * the list supported by the DRM bridge chain.
> >
> > There's nothing restricting it to bridges here. Please rephrase this to
> > remove the
> > bridge mention. The user is typically going to be the encoder, and bridges
> > are just
> > an automagic implementation of an encoder.
> >
>
> OK. I'll fix than in the next version.
>
> > And generally speaking, I'd really like to have an implementation available
> > before
> > merging this.
> >
>
> Well, 2 instances of this callback implementations exist as drafts, as
> this is the new API. A little bit of a chicken and egg problem. I'll
> try to groom at least one of them into upstreamable shape and attach
> it to the patch set.
That's totally what I meant :)
I basically don't want to have an interface that isn't used. If you
provide an implementation in the same series, it's totally reasonable
Maxime
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RE: [PATCH 4/4] drm/atomic-helper: Add select_output_bus_format callback
Hi Maxime,
Thanks for the review.
> -Original Message-
> From: Maxime Ripard
> Sent: Wednesday, February 28, 2024 7:30 AM
> To: Klymenko, Anatoliy
> Cc: Laurent Pinchart ; Maarten Lankhorst
> ; Thomas Zimmermann
> ; David Airlie ; Daniel Vetter
> ; Simek, Michal ; Andrzej Hajda
> ; Neil Armstrong ; Robert
> Foss ; Jonas Karlman ; Jernej Skrabec
> ; dri-devel@lists.freedesktop.org; linux-arm-
> ker...@lists.infradead.org; linux-ker...@vger.kernel.org
> Subject: Re: [PATCH 4/4] drm/atomic-helper: Add select_output_bus_format
> callback
>
> Hi,
>
> On Mon, Feb 26, 2024 at 08:44:45PM -0800, Anatoliy Klymenko wrote:
> > Add select_output_bus_format to CRTC atomic helpers callbacks. This
> > callback Will allow CRTC to participate in media bus format
> > negotiation over connected DRM bridge chain and impose CRTC-specific
> restrictions.
> > A good example is CRTC implemented as FPGA soft IP. This kind of CRTC
> > will most certainly support a single output media bus format, as
> > supporting multiple runtime options consumes extra FPGA resources. A
> > variety of options for FPGA are usually achieved by synthesizing IP
> > with different parameters.
> >
> > Incorporate select_output_bus_format callback into the format
> > negotiation stage to fix the input bus format of the first DRM bridge in the
> chain.
> >
> > Signed-off-by: Anatoliy Klymenko
> > ---
> > drivers/gpu/drm/drm_bridge.c | 19 +--
> > include/drm/drm_modeset_helper_vtables.h | 31
> > +++
> > 2 files changed, 48 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_bridge.c
> > b/drivers/gpu/drm/drm_bridge.c index 521a71c61b16..453ae3d174b4 100644
> > --- a/drivers/gpu/drm/drm_bridge.c
> > +++ b/drivers/gpu/drm/drm_bridge.c
> > @@ -32,6 +32,7 @@
> > #include
> > #include
> > #include
> > +#include
> > #include
> > #include
> >
> > @@ -879,7 +880,8 @@ static int select_bus_fmt_recursive(struct drm_bridge
> *first_bridge,
> > unsigned int i, num_in_bus_fmts = 0;
> > struct drm_bridge_state *cur_state;
> > struct drm_bridge *prev_bridge;
> > - u32 *in_bus_fmts;
> > + struct drm_crtc *crtc = crtc_state->crtc;
> > + u32 *in_bus_fmts, in_fmt;
> > int ret;
> >
> > prev_bridge = drm_bridge_get_prev_bridge(cur_bridge);
> > @@ -933,7 +935,20 @@ static int select_bus_fmt_recursive(struct drm_bridge
> *first_bridge,
> > return -ENOMEM;
> >
> > if (first_bridge == cur_bridge) {
> > - cur_state->input_bus_cfg.format = in_bus_fmts[0];
> > + in_fmt = in_bus_fmts[0];
> > + if (crtc->helper_private &&
> > + crtc->helper_private->select_output_bus_format) {
> > + in_fmt = crtc->helper_private-
> >select_output_bus_format(
> > + crtc,
> > + crtc->state,
> > + in_bus_fmts,
> > + num_in_bus_fmts);
> > + if (!in_fmt) {
> > + kfree(in_bus_fmts);
> > + return -ENOTSUPP;
> > + }
> > + }
> > + cur_state->input_bus_cfg.format = in_fmt;
>
> I don't think we should start poking at the CRTC internals, but we should
> rather
> provide a helper here.
Makes sense, thank you. ACK.
>
> > cur_state->output_bus_cfg.format = out_bus_fmt;
> > kfree(in_bus_fmts);
> > return 0;
> > diff --git a/include/drm/drm_modeset_helper_vtables.h
> > b/include/drm/drm_modeset_helper_vtables.h
> > index 881b03e4dc28..7c21ae1fe3ad 100644
> > --- a/include/drm/drm_modeset_helper_vtables.h
> > +++ b/include/drm/drm_modeset_helper_vtables.h
> > @@ -489,6 +489,37 @@ struct drm_crtc_helper_funcs {
> > bool in_vblank_irq, int *vpos, int *hpos,
> > ktime_t *stime, ktime_t *etime,
> > const struct drm_display_mode *mode);
> > +
> > + /**
> > +* @select_output_bus_format
> > +*
> > +* Called by the first connected DRM bridge to negotiate input media
> > +* bus format. CRTC is expected to pick preferable media formats from
> > +* the list supported by the DRM brid
Re: [PATCH 4/4] drm/atomic-helper: Add select_output_bus_format callback
On Wed, Feb 28, 2024 at 04:29:33PM +0100, Maxime Ripard wrote:
> On Mon, Feb 26, 2024 at 08:44:45PM -0800, Anatoliy Klymenko wrote:
> > Add select_output_bus_format to CRTC atomic helpers callbacks. This
> > callback Will allow CRTC to participate in media bus format negotiation
> > over connected DRM bridge chain and impose CRTC-specific restrictions.
> > A good example is CRTC implemented as FPGA soft IP. This kind of CRTC will
> > most certainly support a single output media bus format, as supporting
> > multiple runtime options consumes extra FPGA resources. A variety of
> > options for FPGA are usually achieved by synthesizing IP with different
> > parameters.
> >
> > Incorporate select_output_bus_format callback into the format negotiation
> > stage to fix the input bus format of the first DRM bridge in the chain.
> >
> > Signed-off-by: Anatoliy Klymenko
> > ---
> > drivers/gpu/drm/drm_bridge.c | 19 +--
> > include/drm/drm_modeset_helper_vtables.h | 31
> > +++
> > 2 files changed, 48 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > index 521a71c61b16..453ae3d174b4 100644
> > --- a/drivers/gpu/drm/drm_bridge.c
> > +++ b/drivers/gpu/drm/drm_bridge.c
> > @@ -32,6 +32,7 @@
> > #include
> > #include
> > #include
> > +#include
> > #include
> > #include
> >
> > @@ -879,7 +880,8 @@ static int select_bus_fmt_recursive(struct drm_bridge
> > *first_bridge,
> > unsigned int i, num_in_bus_fmts = 0;
> > struct drm_bridge_state *cur_state;
> > struct drm_bridge *prev_bridge;
> > - u32 *in_bus_fmts;
> > + struct drm_crtc *crtc = crtc_state->crtc;
> > + u32 *in_bus_fmts, in_fmt;
> > int ret;
> >
> > prev_bridge = drm_bridge_get_prev_bridge(cur_bridge);
> > @@ -933,7 +935,20 @@ static int select_bus_fmt_recursive(struct drm_bridge
> > *first_bridge,
> > return -ENOMEM;
> >
> > if (first_bridge == cur_bridge) {
> > - cur_state->input_bus_cfg.format = in_bus_fmts[0];
> > + in_fmt = in_bus_fmts[0];
> > + if (crtc->helper_private &&
> > + crtc->helper_private->select_output_bus_format) {
> > + in_fmt = crtc->helper_private->select_output_bus_format(
> > + crtc,
> > + crtc->state,
> > + in_bus_fmts,
> > + num_in_bus_fmts);
> > + if (!in_fmt) {
> > + kfree(in_bus_fmts);
> > + return -ENOTSUPP;
> > + }
> > + }
> > + cur_state->input_bus_cfg.format = in_fmt;
>
> I don't think we should start poking at the CRTC internals, but we
> should rather provide a helper here.
It would probably look cleaner, yes.
> > cur_state->output_bus_cfg.format = out_bus_fmt;
> > kfree(in_bus_fmts);
> > return 0;
> > diff --git a/include/drm/drm_modeset_helper_vtables.h
> > b/include/drm/drm_modeset_helper_vtables.h
> > index 881b03e4dc28..7c21ae1fe3ad 100644
> > --- a/include/drm/drm_modeset_helper_vtables.h
> > +++ b/include/drm/drm_modeset_helper_vtables.h
> > @@ -489,6 +489,37 @@ struct drm_crtc_helper_funcs {
> > bool in_vblank_irq, int *vpos, int *hpos,
> > ktime_t *stime, ktime_t *etime,
> > const struct drm_display_mode *mode);
> > +
> > + /**
> > +* @select_output_bus_format
> > +*
> > +* Called by the first connected DRM bridge to negotiate input media
> > +* bus format. CRTC is expected to pick preferable media formats from
> > +* the list supported by the DRM bridge chain.
>
> There's nothing restricting it to bridges here. Please rephrase this to
> remove the bridge mention. The user is typically going to be the
> encoder, and bridges are just an automagic implementation of an encoder.
>
> And generally speaking, I'd really like to have an implementation
> available before merging this.
There's a downstream implementation in the Xilinx kernel, which would
indeed be nice to upstream. This shouldn't block patches 1/4 to 3/4
though, those can be merged once review comments are taken into account.
--
Regards,
Laurent Pinchart
[PATCH 4/4] drm/atomic-helper: Add select_output_bus_format callback
Add select_output_bus_format to CRTC atomic helpers callbacks. This
callback Will allow CRTC to participate in media bus format negotiation
over connected DRM bridge chain and impose CRTC-specific restrictions.
A good example is CRTC implemented as FPGA soft IP. This kind of CRTC will
most certainly support a single output media bus format, as supporting
multiple runtime options consumes extra FPGA resources. A variety of
options for FPGA are usually achieved by synthesizing IP with different
parameters.
Incorporate select_output_bus_format callback into the format negotiation
stage to fix the input bus format of the first DRM bridge in the chain.
Signed-off-by: Anatoliy Klymenko
---
drivers/gpu/drm/drm_bridge.c | 19 +--
include/drm/drm_modeset_helper_vtables.h | 31 +++
2 files changed, 48 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 521a71c61b16..453ae3d174b4 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -32,6 +32,7 @@
#include
#include
#include
+#include
#include
#include
@@ -879,7 +880,8 @@ static int select_bus_fmt_recursive(struct drm_bridge
*first_bridge,
unsigned int i, num_in_bus_fmts = 0;
struct drm_bridge_state *cur_state;
struct drm_bridge *prev_bridge;
- u32 *in_bus_fmts;
+ struct drm_crtc *crtc = crtc_state->crtc;
+ u32 *in_bus_fmts, in_fmt;
int ret;
prev_bridge = drm_bridge_get_prev_bridge(cur_bridge);
@@ -933,7 +935,20 @@ static int select_bus_fmt_recursive(struct drm_bridge
*first_bridge,
return -ENOMEM;
if (first_bridge == cur_bridge) {
- cur_state->input_bus_cfg.format = in_bus_fmts[0];
+ in_fmt = in_bus_fmts[0];
+ if (crtc->helper_private &&
+ crtc->helper_private->select_output_bus_format) {
+ in_fmt = crtc->helper_private->select_output_bus_format(
+ crtc,
+ crtc->state,
+ in_bus_fmts,
+ num_in_bus_fmts);
+ if (!in_fmt) {
+ kfree(in_bus_fmts);
+ return -ENOTSUPP;
+ }
+ }
+ cur_state->input_bus_cfg.format = in_fmt;
cur_state->output_bus_cfg.format = out_bus_fmt;
kfree(in_bus_fmts);
return 0;
diff --git a/include/drm/drm_modeset_helper_vtables.h
b/include/drm/drm_modeset_helper_vtables.h
index 881b03e4dc28..7c21ae1fe3ad 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -489,6 +489,37 @@ struct drm_crtc_helper_funcs {
bool in_vblank_irq, int *vpos, int *hpos,
ktime_t *stime, ktime_t *etime,
const struct drm_display_mode *mode);
+
+ /**
+* @select_output_bus_format
+*
+* Called by the first connected DRM bridge to negotiate input media
+* bus format. CRTC is expected to pick preferable media formats from
+* the list supported by the DRM bridge chain.
+*
+* This callback is optional.
+*
+* Parameters:
+*
+* crtc:
+* The CRTC.
+* crcs_state:
+* New CRTC state.
+* supported_fmts:
+* List of input bus formats supported by the bridge.
+* num_supported_fmts:
+* Number of formats in the list.
+*
+* Returns:
+*
+* Preferred bus format from the list or 0 if CRTC doesn't support any
+* from the provided list.
+*
+*/
+ u32 (*select_output_bus_format)(struct drm_crtc *crtc,
+ struct drm_crtc_state *crtc_state,
+ const u32 *supported_fmts,
+ int num_supported_fmts);
};
/**
--
2.25.1
