linux-kernel - Re:Re: Re:Re: [PATCH v2] drm/arm: fixes pixel clock enabled with wrong format

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Date:   Mon, 18 May 2020 12:06:30 +0800 (GMT+08:00)
From:   Bernard <bernard@...o.com>
To:     Liviu Dudau <liviu.dudau@....com>
Cc:     Brian Starkey <brian.starkey@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        opensource.kernel@...o.com
Subject: Re:Re: Re:Re: [PATCH v2] drm/arm: fixes pixel clock enabled with wrong format


发件人：Liviu Dudau <liviu.dudau@....com>
发送日期：2020-05-15 22:41:49
收件人：Bernard <bernard@...o.com>
抄送人：Brian Starkey <brian.starkey@....com>,David Airlie <airlied@...ux.ie>,Daniel Vetter <daniel@...ll.ch>,dri-devel@...ts.freedesktop.org,linux-kernel@...r.kernel.org,opensource.kernel@...o.com
主题：Re: Re:Re: [PATCH v2] drm/arm: fixes pixel clock enabled with wrong format>Hi Bernard,
>
>On Fri, May 08, 2020 at 04:47:17PM +0800, Bernard wrote:
>> From: "赵军奎" <bernard@...o.com>
>> Date: 2020-04-24 19:37:36
>> To:  Liviu Dudau <liviu.dudau@....com>
>> Cc:  Brian Starkey <brian.starkey@....com>,David Airlie <airlied@...ux.ie>,Daniel Vetter <daniel@...ll.ch>,dri-devel@...ts.freedesktop.org,linux-kernel@...r.kernel.org,opensource.kernel@...o.com
>> Subject: Re:Re: [PATCH v2] drm/arm: fixes pixel clock enabled with wrong format
>> 
>> 
>> 
>> 
>> From: Liviu Dudau <liviu.dudau@....com>
>> Date: 2020-04-24 19:09:50
>> To:  Bernard Zhao <bernard@...o.com>
>> Cc:  Brian Starkey <brian.starkey@....com>,David Airlie <airlied@...ux.ie>,Daniel Vetter <daniel@...ll.ch>,dri-devel@...ts.freedesktop.org,linux-kernel@...r.kernel.org,opensource.kernel@...o.com
>> Subject: Re: [PATCH v2] drm/arm: fixes pixel clock enabled with wrong format>Hi Bernand,
>> >
>> >On Thu, Apr 23, 2020 at 11:35:51PM -0700, Bernard Zhao wrote:
>> >> The pixel clock is still enabled when the format is wrong.
>> >> no error branch handle, and also some register is not set
>> >> in this case, e.g: HDLCD_REG_<color>_SELECT. Maybe we
>> >> should disable this clock and throw an warn message when
>> >> this happened.
>> >> With this change, the code maybe a bit more readable.
>> >> 
>> >> Signed-off-by: Bernard Zhao <bernard@...o.com>
>> >> 
>> >> Changes since V1:
>> >> *add format error handle, if format is not correct, throw
>> >> an warning message and disable this clock.
>> >> 
>> >> Link for V1:
>> >> *https://lore.kernel.org/patchwork/patch/1228501/
>> >> ---
>> >>  drivers/gpu/drm/arm/hdlcd_crtc.c | 13 +++++++++----
>> >>  1 file changed, 9 insertions(+), 4 deletions(-)
>> >> 
>> >> diff --git a/drivers/gpu/drm/arm/hdlcd_crtc.c b/drivers/gpu/drm/arm/hdlcd_crtc.c
>> >> index af67fefed38d..f3945dee2b7d 100644
>> >> --- a/drivers/gpu/drm/arm/hdlcd_crtc.c
>> >> +++ b/drivers/gpu/drm/arm/hdlcd_crtc.c
>> >> @@ -96,7 +96,7 @@ static int hdlcd_set_pxl_fmt(struct drm_crtc *crtc)
>> >>  	}
>> >>  
>> >>  	if (WARN_ON(!format))
>> >> -		return 0;
>> >> +		return -EINVAL;
>> >
>> >That is the right fix!
>> >
>> >>  
>> >>  	/* HDLCD uses 'bytes per pixel', zero means 1 byte */
>> >>  	btpp = (format->bits_per_pixel + 7) / 8;
>> >> @@ -125,7 +125,7 @@ static int hdlcd_set_pxl_fmt(struct drm_crtc *crtc)
>> >>  	return 0;
>> >>  }
>> >>  
>> >> -static void hdlcd_crtc_mode_set_nofb(struct drm_crtc *crtc)
>> >> +static int hdlcd_crtc_mode_set_nofb(struct drm_crtc *crtc)
>> >
>> >But this is not. We don't need to propagate the error further, just ....
>> >
>> >>  {
>> >>  	struct hdlcd_drm_private *hdlcd = crtc_to_hdlcd_priv(crtc);
>> >>  	struct drm_display_mode *m = &crtc->state->adjusted_mode;
>> >> @@ -162,9 +162,10 @@ static void hdlcd_crtc_mode_set_nofb(struct drm_crtc *crtc)
>> >>  
>> >>  	err = hdlcd_set_pxl_fmt(crtc);
>> >>  	if (err)
>> >> -		return;
>> >
>> 
>> My previous understanding was that when such an exception occurred, it was caught
>> in the atomic_enable interface, and then disable pixel clock. I am not sure is this ok or
>> i have to do more register clean operaction.
>> 
>> >... return here so that we don't call clk_set_rate();
>> And for this part, i am a little confused :
>> 1 clk_set_rate must be set even if format is wrong?
>> 2 The original code logic shows that If format is not correct, we will not set registers 
>> HDLCD_REG_PIXEL_FORMAT & HDLCD_REG_<color>_SELECT, will this bring in
>> any problems?
>> 3 if 1 the rate must set & 2 registers above doesn`t matter, then maybe there is no
>> need to disable pixel clock.
>> Am i misunderstanding
>
>You are right, the pixel format check should not happen inside hdlcd_crtc_atomic_enable()
>hook, it should be moved into a separate function hdlcd_crtc_atomic_check() and that needs
>to be hooked into .atomic_check() for hdlcd_crtc_helper_funcs().
>
>If you want to have another go I'll be happy to review and Ack your patch.
>
>Best regards,
>Liviu 
>

Hi

Sure, i will check this and re-subbmit one patch.

Regards,
Bernard

>> 
>> Regards,
>> Bernard
>> 
>> >> +		return err;
>> >>  
>> >>  	clk_set_rate(hdlcd->clk, m->crtc_clock * 1000);
>> >> +	return 0;
>> >>  }
>> >>  
>> >>  static void hdlcd_crtc_atomic_enable(struct drm_crtc *crtc,
>> >> @@ -173,7 +174,11 @@ static void hdlcd_crtc_atomic_enable(struct drm_crtc *crtc,
>> >>  	struct hdlcd_drm_private *hdlcd = crtc_to_hdlcd_priv(crtc);
>> >>  
>> >>  	clk_prepare_enable(hdlcd->clk);
>> >> -	hdlcd_crtc_mode_set_nofb(crtc);
>> >> +	if (hdlcd_crtc_mode_set_nofb(crtc)) {
>> >> +		DRM_DEBUG_KMS("Invalid format, pixel clock enable failed!\n");
>> >> +		clk_disable_unprepare(hdlcd->clk);
>> >> +		return;
>> >> +	}
>> >>  	hdlcd_write(hdlcd, HDLCD_REG_COMMAND, 1);
>> >>  	drm_crtc_vblank_on(crtc);
>> >>  }
>> >> -- 
>> >> 2.26.2
>> >> 
>> >
>> >-- 
>> >====================
>> >| I would like to |
>> >| fix the world,  |
>> >| but they're not |
>> >| giving me the   |
>> > \ source code!  /
>> >  ---------------
>> >    ¯\_(ツ)_/¯
>> 
>> 
>> 
>
>-- 
>====================
>| I would like to |
>| fix the world,  |
>| but they're not |
>| giving me the   |
> \ source code!  /
>  ---------------
>    ¯\_(ツ)_/¯