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

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Date: Wed, 10 Jan 2024 17:21:47 +0100
From: Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
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 12/21/23 14:17, Dmitry Baryshkov wrote:
> 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)


Hi Dmitry,

This patch needs rework. I'll drop it for now and send it back later when it is
more mature.

Regards,

Raphaël

>
>> 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
>>
>