Re: [PATCH] drm/arcpgu: use .mode_fixup instead of .atomic_check

[Alexey Brodkin]

Hi Daniel,

On Thu, 2017-03-02 at 20:54 +0100, Daniel Vetter wrote:
> On Thu, Mar 02, 2017 at 08:27:54PM +0300, Alexey Brodkin wrote:
> > 
> > Since we cannot always generate exactly requested pixel clock
> > there's not much sense in checking requested_clock == clk_round_rate().
> > In that case for quite some modes we'll be getting -EINVAL and no video
> > output at all.
> > 
> > But given there's some tolerance to real pixel clock in TVs/monitors
> > we may still give it a try with the clock as close to requested one as
> > PLL on the board may generate. So we just do a fixup to what current
> > board may provide.
> > 
> > Signed-off-by: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > Cc: David Airlie <airlied@xxxxxxxx>
> > Cc: Jose Abreu <joabreu@xxxxxxxxxxxx>
> > ---
> > Âdrivers/gpu/drm/arc/arcpgu_crtc.c | 16 +++++++---------
> > Â1 file changed, 7 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/arc/arcpgu_crtc.c b/drivers/gpu/drm/arc/arcpgu_crtc.c
> > index ad9a95916f1f..3f2823c1efc3 100644
> > --- a/drivers/gpu/drm/arc/arcpgu_crtc.c
> > +++ b/drivers/gpu/drm/arc/arcpgu_crtc.c
> > @@ -129,18 +129,16 @@ static void arc_pgu_crtc_disable(struct drm_crtc *crtc)
> > Â			ÂÂÂÂÂÂ~ARCPGU_CTRL_ENABLE_MASK);
> > Â}
> > Â
> > -static int arc_pgu_crtc_atomic_check(struct drm_crtc *crtc,
> > -				ÂÂÂÂÂstruct drm_crtc_state *state)
> > +static bool arc_pgu_crtc_mode_fixup(struct drm_crtc *crtc,
> > +				ÂÂÂÂconst struct drm_display_mode *mode,
> > +				ÂÂÂÂstruct drm_display_mode *adjusted_mode)
> 
> This isn't required at all, see drm_crtc_state.adjusted_mode. Just update
> that and you're good - .mode_fixup is the backwards compatibility function
> for old kms drivers, atomic_check is strictly more powerful.

So if I understood you correct here what I really need is just to get rid of existing check,
right? I.e. the following is to be in v2 respin:
------------------------------->8-------------------------------
diff --git a/drivers/gpu/drm/arc/arcpgu_crtc.c b/drivers/gpu/drm/arc/arcpgu_crtc.c
index ad9a95916f1f..86f1555914e8 100644
--- a/drivers/gpu/drm/arc/arcpgu_crtc.c
+++ b/drivers/gpu/drm/arc/arcpgu_crtc.c
@@ -129,20 +129,6 @@ static void arc_pgu_crtc_disable(struct drm_crtc *crtc)
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ~ARCPGU_CTRL_ENABLE_MASK);
Â}
Â
-static int arc_pgu_crtc_atomic_check(struct drm_crtc *crtc,
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂstruct drm_crtc_state *state)
-{
-ÂÂÂÂÂÂÂstruct arcpgu_drm_private *arcpgu = crtc_to_arcpgu_priv(crtc);
-ÂÂÂÂÂÂÂstruct drm_display_mode *mode = &state->adjusted_mode;
-ÂÂÂÂÂÂÂlong rate, clk_rate = mode->clock * 1000;
-
-ÂÂÂÂÂÂÂrate = clk_round_rate(arcpgu->clk, clk_rate);
-ÂÂÂÂÂÂÂif (rate != clk_rate)
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂreturn -EINVAL;
-
-ÂÂÂÂÂÂÂreturn 0;
-}
-
Âstatic void arc_pgu_crtc_atomic_begin(struct drm_crtc *crtc,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂstruct drm_crtc_state *state)
Â{
@@ -165,7 +151,6 @@ static const struct drm_crtc_helper_funcs arc_pgu_crtc_helper_funcs = {
ÂÂÂÂÂÂÂÂ.disableÂÂÂÂÂÂÂÂ= arc_pgu_crtc_disable,
ÂÂÂÂÂÂÂÂ.prepareÂÂÂÂÂÂÂÂ= arc_pgu_crtc_disable,
ÂÂÂÂÂÂÂÂ.commitÂÂÂÂÂÂÂÂÂ= arc_pgu_crtc_enable,
-ÂÂÂÂÂÂÂ.atomic_checkÂÂÂ= arc_pgu_crtc_atomic_check,
ÂÂÂÂÂÂÂÂ.atomic_beginÂÂÂ= arc_pgu_crtc_atomic_begin,
Â};
------------------------------->8-------------------------------

> Please also make sure the documentation properly explains this, and if
> not, please submit a patch to improve it.

You mean explains what? That .mode_fixup is not meant to be used in
new code?

-Alexey