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Message-ID: <20220217223912.xl5ofq3aoy44p4vv@SoMainline.org>
Date: Thu, 17 Feb 2022 23:39:12 +0100
From: Marijn Suijten <marijn.suijten@...ainline.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Vinod Koul <vkoul@...nel.org>, Rob Clark <robdclark@...il.com>,
linux-arm-msm@...r.kernel.org,
Bjorn Andersson <bjorn.andersson@...aro.org>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Jonathan Marek <jonathan@...ek.ca>,
Abhinav Kumar <abhinavk@...eaurora.org>,
Jeffrey Hugo <jeffrey.l.hugo@...il.com>,
Sumit Semwal <sumit.semwal@...aro.org>,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
freedreno@...ts.freedesktop.org
Subject: Re: [PATCH v3 03/13] drm/msm/disp/dpu1: Add support for DSC in
pingpong block
On 2022-02-18 01:12:02, Dmitry Baryshkov wrote:
> On 18/02/2022 00:54, Marijn Suijten wrote:
> > On 2021-11-16 11:52:46, Vinod Koul wrote:
> >> In SDM845, DSC can be enabled by writing to pingpong block registers, so
> >> add support for DSC in hw_pp
> >
> > Nit: I don't think the ", so add support for DSC in XXX" part in this
> > and other commit messages add anything. You've already stated that in
> > the title, the commit body is just extra justification (and can perhaps
> > be filled with extra details about the patch contents instead).
> >
> >> Reviewed-by: Abhinav Kumar <abhinavk@...eaurora.org>
> >> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> >> Signed-off-by: Vinod Koul <vkoul@...nel.org>
> >> ---
> >> .../gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c | 32 +++++++++++++++++++
> >> .../gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.h | 14 ++++++++
> >> 2 files changed, 46 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c
> >> index 55766c97c4c8..47c6ab6caf95 100644
> >> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c
> >> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c
> >> @@ -28,6 +28,9 @@
> >> #define PP_FBC_MODE 0x034
> >> #define PP_FBC_BUDGET_CTL 0x038
> >> #define PP_FBC_LOSSY_MODE 0x03C
> >> +#define PP_DSC_MODE 0x0a0
> >> +#define PP_DCE_DATA_IN_SWAP 0x0ac
> >
> > This enum does not seem used here, is it used in another patch?
> >
> >> +#define PP_DCE_DATA_OUT_SWAP 0x0c8
> >>
> >> #define PP_DITHER_EN 0x000
> >> #define PP_DITHER_BITDEPTH 0x004
> >> @@ -245,6 +248,32 @@ static u32 dpu_hw_pp_get_line_count(struct dpu_hw_pingpong *pp)
> >> return line;
> >> }
> >>
> >> +static int dpu_hw_pp_dsc_enable(struct dpu_hw_pingpong *pp)
> >> +{
> >> + struct dpu_hw_blk_reg_map *c = &pp->hw;
> >> +
> >> + DPU_REG_WRITE(c, PP_DSC_MODE, 1);
> >> + return 0;
> >> +}
> >> +
> >> +static void dpu_hw_pp_dsc_disable(struct dpu_hw_pingpong *pp)
> >> +{
> >> + struct dpu_hw_blk_reg_map *c = &pp->hw;
> >> +
> >> + DPU_REG_WRITE(c, PP_DSC_MODE, 0);
> >> +}
> >> +
> >> +static int dpu_hw_pp_setup_dsc(struct dpu_hw_pingpong *pp)
> >> +{
> >> + struct dpu_hw_blk_reg_map *pp_c = &pp->hw;
> >> + int data;
> >> +
> >> + data = DPU_REG_READ(pp_c, PP_DCE_DATA_OUT_SWAP);
> >> + data |= BIT(18); /* endian flip */
> >> + DPU_REG_WRITE(pp_c, PP_DCE_DATA_OUT_SWAP, data);
> >> + return 0;
> >> +}
> >> +
> >> static void _setup_pingpong_ops(struct dpu_hw_pingpong *c,
> >> unsigned long features)
> >> {
> >> @@ -256,6 +285,9 @@ static void _setup_pingpong_ops(struct dpu_hw_pingpong *c,
> >> c->ops.get_autorefresh = dpu_hw_pp_get_autorefresh_config;
> >> c->ops.poll_timeout_wr_ptr = dpu_hw_pp_poll_timeout_wr_ptr;
> >> c->ops.get_line_count = dpu_hw_pp_get_line_count;
> >> + c->ops.setup_dsc = dpu_hw_pp_setup_dsc;
> >> + c->ops.enable_dsc = dpu_hw_pp_dsc_enable;
> >> + c->ops.disable_dsc = dpu_hw_pp_dsc_disable;
> >>
> >> if (test_bit(DPU_PINGPONG_DITHER, &features))
> >> c->ops.setup_dither = dpu_hw_pp_setup_dither;
> >> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.h
> >> index 89d08a715c16..12758468d9ca 100644
> >> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.h
> >> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.h
> >> @@ -124,6 +124,20 @@ struct dpu_hw_pingpong_ops {
> >> */
> >> void (*setup_dither)(struct dpu_hw_pingpong *pp,
> >> struct dpu_hw_dither_cfg *cfg);
> >> + /**
> >> + * Enable DSC
> >> + */
> >> + int (*enable_dsc)(struct dpu_hw_pingpong *pp);
> >> +
> >> + /**
> >> + * Disable DSC
> >> + */
> >> + void (*disable_dsc)(struct dpu_hw_pingpong *pp);
> >
> > It looks like most other callbacks in dpu1 use an `enable` function with
> > a boolean, instead of having a separate disable function. That should
> > simplify the implementation down to a single ternary-if, too. Would
> > that be desired to use here?
>
> Just my 2c. I personally hate the unified functions with the boolean
> argument. One of the reasons being the return value. Typically you do
> not expect that the disable function can fail (or return an error). But
> the unified function provides an error (to be handled) even in the
> disable case.
>
> Last, but not least, overall the kernel API is biased towards separate
> enable and disable calls.
Fair enough, we should replace the other functions then. Or perhaps
drop the return argument entirely, it's always zero for enable_dsc
anyway. I doubt we'll ever add additional checks here? If we do,
things can be split again.
- Marijn
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