Subject: Re: [EXT] Re: [PATCH v2 12/15] drm/mxsfb: Improve the axi clock usage

From: Robert Chiras <[email-masked]>
Date: Wed, 14 Aug 2019 11:35:15 +0000

Hi Stefan,

On Mi, 2019-08-14 at 13:06 +0200, Stefan Agner wrote:
> On 2019-08-14 12:48, Robert Chiras wrote:
> > 
> > Currently, the enable of the axi clock return status is ignored,
> > causing
> > issues when the enable fails then we try to disable it. Therefore,
> > it is
> > better to check the return status and disable it only when enable
> > succeeded.
> Is this actually the case in real world sometimes? Why is it failing?
When I noticed that fail, we had some restrictions in SCU firmware, so
that the clock cannot be enabled if the power domain was down. Still,
at that time I noticed it is redundant to have functions that checks if
a clock is NULL or not, since the clk_* functions are already doing
this.
> 
> I guess if we do this in one place, we should do it in all places
> (e.g.
> also in mxsfb_crtc_enable, mxsfb_plane_atomic_update..)
I add specific checks only in the vblank functions, because those
functions can be called before calling the pipe enable/disable
functions which enables the spefic power domain and, at this point, the
clock enable/disable calls should not fail.
> 
> --
> Stefan
> 
> > 
> > Also, remove the helper functions around clk_axi, since we can
> > directly
> > use the clk API function for enable/disable the clock. Those
> > functions
> > are already checking for NULL clk and returning 0 if that's the
> > case.
> 
> > 
> > 
> > Signed-off-by: Robert Chiras <[email-masked]>
> > Acked-by: Leonard Crestez <[email-masked]>
> > ---
> >  drivers/gpu/drm/mxsfb/mxsfb_crtc.c |  8 ++++----
> >  drivers/gpu/drm/mxsfb/mxsfb_drv.c  | 32 +++++++++++++-------------
> > ------
> >  drivers/gpu/drm/mxsfb/mxsfb_drv.h  |  3 ---
> >  3 files changed, 17 insertions(+), 26 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> > b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> > index a4ba368..e727f5e 100644
> > --- a/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> > +++ b/drivers/gpu/drm/mxsfb/mxsfb_crtc.c
> > @@ -408,7 +408,7 @@ void mxsfb_crtc_enable(struct mxsfb_drm_private
> > *mxsfb)
> >  {
> >       dma_addr_t paddr;
> > 
> > -     mxsfb_enable_axi_clk(mxsfb);
> > +     clk_prepare_enable(mxsfb->clk_axi);
> >       writel(0, mxsfb->base + LCDC_CTRL);
> >       mxsfb_crtc_mode_set_nofb(mxsfb);
> > 
> > @@ -425,7 +425,7 @@ void mxsfb_crtc_enable(struct mxsfb_drm_private
> > *mxsfb)
> >  void mxsfb_crtc_disable(struct mxsfb_drm_private *mxsfb)
> >  {
> >       mxsfb_disable_controller(mxsfb);
> > -     mxsfb_disable_axi_clk(mxsfb);
> > +     clk_disable_unprepare(mxsfb->clk_axi);
> >  }
> > 
> >  void mxsfb_plane_atomic_update(struct mxsfb_drm_private *mxsfb,
> > @@ -451,8 +451,8 @@ void mxsfb_plane_atomic_update(struct
> > mxsfb_drm_private *mxsfb,
> > 
> >       paddr = mxsfb_get_fb_paddr(mxsfb);
> >       if (paddr) {
> > -             mxsfb_enable_axi_clk(mxsfb);
> > +             clk_prepare_enable(mxsfb->clk_axi);
> >               writel(paddr, mxsfb->base + mxsfb->devdata-
> > >next_buf);
> > -             mxsfb_disable_axi_clk(mxsfb);
> > +             clk_disable_unprepare(mxsfb->clk_axi);
> >       }
> >  }
> > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > index 6dae2bd..694b287 100644
> > --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > @@ -97,18 +97,6 @@ drm_pipe_to_mxsfb_drm_private(struct
> > drm_simple_display_pipe *pipe)
> >       return container_of(pipe, struct mxsfb_drm_private, pipe);
> >  }
> > 
> > -void mxsfb_enable_axi_clk(struct mxsfb_drm_private *mxsfb)
> > -{
> > -     if (mxsfb->clk_axi)
> > -             clk_prepare_enable(mxsfb->clk_axi);
> > -}
> > -
> > -void mxsfb_disable_axi_clk(struct mxsfb_drm_private *mxsfb)
> > -{
> > -     if (mxsfb->clk_axi)
> > -             clk_disable_unprepare(mxsfb->clk_axi);
> > -}
> > -
> >  /**
> >   * mxsfb_atomic_helper_check - validate state object
> >   * @dev: DRM device
> > @@ -229,25 +217,31 @@ static void mxsfb_pipe_update(struct
> > drm_simple_display_pipe *pipe,
> >  static int mxsfb_pipe_enable_vblank(struct drm_simple_display_pipe
> > *pipe)
> >  {
> >       struct mxsfb_drm_private *mxsfb =
> > drm_pipe_to_mxsfb_drm_private(pipe);
> > +     int ret = 0;
> > +
> > +     ret = clk_prepare_enable(mxsfb->clk_axi);
> > +     if (ret)
> > +             return ret;
> > 
> >       /* Clear and enable VBLANK IRQ */
> > -     mxsfb_enable_axi_clk(mxsfb);
> >       writel(CTRL1_CUR_FRAME_DONE_IRQ, mxsfb->base + LCDC_CTRL1 +
> > REG_CLR);
> >       writel(CTRL1_CUR_FRAME_DONE_IRQ_EN, mxsfb->base + LCDC_CTRL1
> > + REG_SET);
> > -     mxsfb_disable_axi_clk(mxsfb);
> > +     clk_disable_unprepare(mxsfb->clk_axi);
> > 
> > -     return 0;
> > +     return ret;
> >  }
> > 
> >  static void mxsfb_pipe_disable_vblank(struct
> > drm_simple_display_pipe *pipe)
> >  {
> >       struct mxsfb_drm_private *mxsfb =
> > drm_pipe_to_mxsfb_drm_private(pipe);
> > 
> > +     if (clk_prepare_enable(mxsfb->clk_axi))
> > +             return;
> > +
> >       /* Disable and clear VBLANK IRQ */
> > -     mxsfb_enable_axi_clk(mxsfb);
> >       writel(CTRL1_CUR_FRAME_DONE_IRQ_EN, mxsfb->base + LCDC_CTRL1
> > + REG_CLR);
> >       writel(CTRL1_CUR_FRAME_DONE_IRQ, mxsfb->base + LCDC_CTRL1 +
> > REG_CLR);
> > -     mxsfb_disable_axi_clk(mxsfb);
> > +     clk_disable_unprepare(mxsfb->clk_axi);
> >  }
> > 
> >  static struct drm_simple_display_pipe_funcs mxsfb_funcs = {
> > @@ -413,7 +407,7 @@ static irqreturn_t mxsfb_irq_handler(int irq,
> > void *data)
> >       struct mxsfb_drm_private *mxsfb = drm->dev_private;
> >       u32 reg;
> > 
> > -     mxsfb_enable_axi_clk(mxsfb);
> > +     clk_prepare_enable(mxsfb->clk_axi);
> > 
> >       reg = readl(mxsfb->base + LCDC_CTRL1);
> > 
> > @@ -422,7 +416,7 @@ static irqreturn_t mxsfb_irq_handler(int irq,
> > void *data)
> > 
> >       writel(CTRL1_CUR_FRAME_DONE_IRQ, mxsfb->base + LCDC_CTRL1 +
> > REG_CLR);
> > 
> > -     mxsfb_disable_axi_clk(mxsfb);
> > +     clk_disable_unprepare(mxsfb->clk_axi);
> > 
> >       return IRQ_HANDLED;
> >  }
> > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.h
> > b/drivers/gpu/drm/mxsfb/mxsfb_drv.h
> > index 8fb65d3..d6df8fe 100644
> > --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.h
> > +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.h
> > @@ -37,9 +37,6 @@ struct mxsfb_drm_private {
> >  int mxsfb_setup_crtc(struct drm_device *dev);
> >  int mxsfb_create_output(struct drm_device *dev);
> > 
> > -void mxsfb_enable_axi_clk(struct mxsfb_drm_private *mxsfb);
> > -void mxsfb_disable_axi_clk(struct mxsfb_drm_private *mxsfb);
> > -
> >  void mxsfb_crtc_enable(struct mxsfb_drm_private *mxsfb);
> >  void mxsfb_crtc_disable(struct mxsfb_drm_private *mxsfb);
> >  void mxsfb_plane_atomic_update(struct mxsfb_drm_private *mxsfb,

Thanks,
Robert
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