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

From: Emil Velikov
Date: Fri Apr 24 2020 - 07:02:48 EST


Hi Bernard,

On Fri, 24 Apr 2020 at 08:15, Bernard Zhao <bernard@xxxxxxxx> 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@xxxxxxxx>
>
> 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;
>
> /* 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)
> {
> 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;
> + 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;
> + }
This doesn't seem right. As far as I can tell, the state must be
checked in the .atomic_check since .atomic_enable, intentionally,
"cannot" fail.

HTH
Emil


> hdlcd_write(hdlcd, HDLCD_REG_COMMAND, 1);
> drm_crtc_vblank_on(crtc);
> }
> --
> 2.26.2
>
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