linux-kernel - Re: [PATCH RESEND v1 4/8] drm/stm: ltdc: implement bus clock

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Message-ID: <CAA8EJpq-NWUEe8QbUwDHu0BBSViWKh92PujD7PA84xgvSUsvhg@mail.gmail.com>
Date: Thu, 21 Dec 2023 15:17:31 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Sam Ravnborg <sam@...nborg.org>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Maxime Coquelin <mcoquelin.stm32@...il.com>, Alexandre Torgue <alexandre.torgue@...s.st.com>, 
	Yannick Fertre <yannick.fertre@...s.st.com>, Philippe Cornu <philippe.cornu@...s.st.com>, 
	Philipp Zabel <p.zabel@...gutronix.de>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, 
	Thierry Reding <thierry.reding@...il.com>, linux-arm-kernel@...ts.infradead.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH RESEND v1 4/8] drm/stm: ltdc: implement bus clock

On Thu, 21 Dec 2023 at 14:45, Raphael Gallais-Pou
<raphael.gallais-pou@...s.st.com> wrote:
>
> From: Yannick Fertre <yannick.fertre@...s.st.com>
>
> The latest hardware version of the LTDC presents the addition of a bus
> clock, which contains the global configuration registers and the interrupt
> register.
>
> Signed-off-by: Yannick Fertre <yannick.fertre@...s.st.com>
> ---
>  drivers/gpu/drm/stm/ltdc.c | 8 ++++++++
>  drivers/gpu/drm/stm/ltdc.h | 1 +
>  2 files changed, 9 insertions(+)

I might be missing something, but I don't see this clock being set
(compare this patch to the patch 5/8)

>
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index 5576fdae4962..67064f47a4cb 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -1896,6 +1896,8 @@ void ltdc_suspend(struct drm_device *ddev)
>
>         DRM_DEBUG_DRIVER("\n");
>         clk_disable_unprepare(ldev->pixel_clk);
> +       if (ldev->bus_clk)
> +               clk_disable_unprepare(ldev->bus_clk);
>  }
>
>  int ltdc_resume(struct drm_device *ddev)
> @@ -1910,6 +1912,12 @@ int ltdc_resume(struct drm_device *ddev)
>                 DRM_ERROR("failed to enable pixel clock (%d)\n", ret);
>                 return ret;
>         }
> +       if (ldev->bus_clk) {
> +               if (clk_prepare_enable(ldev->bus_clk)) {
> +                       DRM_ERROR("Unable to prepare bus clock\n");
> +                       return -ENODEV;
> +               }
> +       }
>
>         return 0;
>  }
> diff --git a/drivers/gpu/drm/stm/ltdc.h b/drivers/gpu/drm/stm/ltdc.h
> index 9d488043ffdb..155d8e4a7c6b 100644
> --- a/drivers/gpu/drm/stm/ltdc.h
> +++ b/drivers/gpu/drm/stm/ltdc.h
> @@ -44,6 +44,7 @@ struct ltdc_device {
>         void __iomem *regs;
>         struct regmap *regmap;
>         struct clk *pixel_clk;  /* lcd pixel clock */
> +       struct clk *bus_clk;    /* bus clock */
>         struct mutex err_lock;  /* protecting error_status */
>         struct ltdc_caps caps;
>         u32 irq_status;
> --
> 2.25.1
>


-- 
With best wishes
Dmitry