[PATCH v3,2/4] drm/mediatek: Separate poweron/poweroff from enable/disable and define new funcs

[xinlei.lee]

On Wed, 2022-03-23 at 19:46 +0800, Rex-BC Chen wrote:
> On Tue, 2022-03-22 at 17:23 +0800, xinlei.lee wrote:
> > On Thu, 2022-03-17 at 20:02 +0800, Rex-BC Chen wrote:
> > > Hello Xinlei,
> > > 
> > > On Thu, 2022-03-17 at 15:53 +0800, xinlei.lee at mediatek.com wrote:
> > > > From: Jitao Shi <jitao.shi at mediatek.com>
> > > > 
> > > > In order to match the changes of "Use the drm_panel_bridge
> > > > API",
> > > > the poweron/poweroff of dsi is extracted from enable/disable
> > > > and
> > > > defined as new funcs (pre_enable/post_disable).
> > > > 
> > > > Fixes: 2dd8075d2185 ("drm/mediatek: mtk_dsi: Use the
> > > > drm_panel_bridge
> > > > API")
> > > > 
> > > > Signed-off-by: Jitao Shi <jitao.shi at mediatek.com>
> > > > Signed-off-by: Xinlei Lee <xinlei.lee at mediatek.com>
> > > > ---
> > > >  drivers/gpu/drm/mediatek/mtk_dsi.c | 45 +++++++++++++++++-----
> > > > --
> > > > --
> > > > --
> > > > --
> > > >  1 file changed, 26 insertions(+), 19 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > > b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > > index 262c027d8c2f..e33caaca11a7 100644
> > > > --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > > +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > > @@ -679,16 +679,6 @@ static void mtk_dsi_poweroff(struct
> > > > mtk_dsi
> > > > *dsi)
> > > >  	if (--dsi->refcount != 0)
> > > >  		return;
> > > >  
> > > > -	/*
> > > > -	 * mtk_dsi_stop() and mtk_dsi_start() is asymmetric,
> > > > since
> > > > -	 * mtk_dsi_stop() should be called after
> > > > mtk_drm_crtc_atomic_disable(),
> > > > -	 * which needs irq for vblank, and mtk_dsi_stop() will
> > > > disable
> > > > irq.
> > > > -	 * mtk_dsi_start() needs to be called in
> > > > mtk_output_dsi_enable(),
> > > > -	 * after dsi is fully set.
> > > > -	 */
> > > > -	mtk_dsi_stop(dsi);
> > > > -
> > > > -	mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
> > > >  	mtk_dsi_reset_engine(dsi);
> > > >  	mtk_dsi_lane0_ulp_mode_enter(dsi);
> > > >  	mtk_dsi_clk_ulp_mode_enter(dsi);
> > > > @@ -703,17 +693,9 @@ static void mtk_dsi_poweroff(struct
> > > > mtk_dsi
> > > > *dsi)
> > > >  
> > > >  static void mtk_output_dsi_enable(struct mtk_dsi *dsi)
> > > >  {
> > > > -	int ret;
> > > > -
> > > >  	if (dsi->enabled)
> > > >  		return;
> > > >  
> > > > -	ret = mtk_dsi_poweron(dsi);
> > > > -	if (ret < 0) {
> > > > -		DRM_ERROR("failed to power on dsi\n");
> > > > -		return;
> > > > -	}
> > > > -
> > > >  	mtk_dsi_set_mode(dsi);
> > > >  	mtk_dsi_clk_hs_mode(dsi, 1);
> > > >  
> > > > @@ -727,7 +709,16 @@ static void mtk_output_dsi_disable(struct
> > > > mtk_dsi *dsi)
> > > >  	if (!dsi->enabled)
> > > >  		return;
> > > >  
> > > > -	mtk_dsi_poweroff(dsi);
> > > > +	/*
> > > > +	 * mtk_dsi_stop() and mtk_dsi_start() is asymmetric,
> > > > since
> > > 
> > > Why they are asymmetric?
> > > 
> > > > +	 * mtk_dsi_stop() should be called after
> > > > mtk_drm_crtc_atomic_disable(),
> > > > +	 * which needs irq for vblank, and mtk_dsi_stop() will
> > > > disable
> > > > irq.
> > > > +	 * mtk_dsi_start() needs to be called in
> > > > mtk_output_dsi_enable(),
> > > > +	 * after dsi is fully set.
> > > > +	 */
> > > > +	mtk_dsi_stop(dsi);
> > > > +
> > > > +	mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
> > > >  
> > > >  	dsi->enabled = false;
> > > >  }
> > > > @@ -765,10 +756,26 @@ static void mtk_dsi_bridge_enable(struct
> > > > drm_bridge *bridge)
> > > >  	mtk_output_dsi_enable(dsi);
> > > >  }
> > > >  
> > > > +static void mtk_dsi_bridge_pre_enable(struct drm_bridge
> > > > *bridge)
> > > > +{
> > > > +	struct mtk_dsi *dsi = bridge_to_dsi(bridge);
> > > > +
> > > > +	mtk_dsi_poweron(dsi);
> > > 
> > > Should you handle the error of mtk_dsi_poweron?
> > > If you failed to mtk_dsi_bridge_pre_enable and do
> > > mtk_dsi_bridge_enable,
> > > what will happend?
> > > 
> > > > +}
> > > > +
> > > > +static void mtk_dsi_bridge_post_disable(struct drm_bridge
> > > > *bridge)
> > > > +{
> > > > +	struct mtk_dsi *dsi = bridge_to_dsi(bridge);
> > > > +
> > > > +	mtk_dsi_poweroff(dsi);
> > > 
> > > If you failed to mtk_dsi_bridge_disable and you do
> > > mtk_dsi_bridge_post_disable,
> > > what will happend?
> > > Do you need to handle this?
> > > 
> > > BRs,
> > > Rex
> > > 
> > > > +}
> > > > +
> > > >  static const struct drm_bridge_funcs mtk_dsi_bridge_funcs = {
> > > >  	.attach = mtk_dsi_bridge_attach,
> > > >  	.disable = mtk_dsi_bridge_disable,
> > > >  	.enable = mtk_dsi_bridge_enable,
> > > > +	.pre_enable = mtk_dsi_bridge_pre_enable,
> > > > +	.post_disable = mtk_dsi_bridge_post_disable,
> > > >  	.mode_set = mtk_dsi_bridge_mode_set,
> > > >  };
> > > >  
> > > 
> > > 
> > 
> > Hi Rex:
> > 
> > Thanks for your review!
> > 
> > 1.Why they are asymmetric?
> > =>My understanding mtk_dsi_stop() and mtk_dsi_start() is to make
> > dsi
> > switch from LP11 and HS mode.DSI has two working modes:
> > If it is cmd mode, the data sent is sent by LP11, and dsi_start is
> > just
> > a signal. In this mode, dsi_stop is not required after sending cmd.
> > If it is video mode, because the data needs to be sent in HS mode,
> > dsi_start is required to make dsi enter HS mode from LP11. After
> > suspend, drm will call dsi_disable, and call dsi_stop to make dsi
> > return from HS mode to LP11 state.
> > Therefore mtk_dsi_stop() and mtk_dsi_start() are asymmetric.
> > For example, in the dsi_host_transfer function, only dsi_stop has
> > no
> > dsi_start operation.
> > 
> > 2.
> > Because the return type of pre_enable & post_disable in common code
> > is
> > void type. If there is an error, it will be processed in
> > poweron/poweroff, and the error message will be printed.
> > Do you mean that pre_enable & post_disable needs to accept the
> > poweron/poweroff error return value and then print the error log?
> > 
> > 3.
> > If pre_enable fails, there is only a problem with the dsi module,
> > and
> > it does not affect the execution of other modules and enable funcs
> > under drm. 
> > Same goes for post_disable & disable.
> > 
> > Best Regrds!
> > xinlei
> > 
> 
> Hello Xinlei,
> 
> about failure for mtk_dsi_poweron(), it is all becuase of error
> setting
> for clock.
> If we do not set clock correctly and not enable DSI, after set DSI
> start, will it cause any issue? (maybe bus hang or something.)
> 
> Because in original drivers, if mtk_dsi_poweron failed, the DSI will
> not start.
> 
> IMO, it also needs some error message for mtk_dsi_bridge_pre_enable()
> and mtk_dsi_bridge_post_disable().
> 
> BRs,
> Rex
> 

Hi Rex:

Thanks for your review.
In the original dsi_poweron, if (++dsi->refcount != 1) is used to
determine whether poweron has been repeatedly run.
The poweron failure to execute DSI Start you mentioned may indeed lead
to Bus hang in extreme cases, so I will add a poweron-like judgment
mechanism before the next version of enable.
And will add some error message for mtk_dsi_bridge_pre_enable() and
mtk_dsi_bridge_post_disable().

Best Regards!
xinlei