linux-kernel - Re: [PATCH 2/3] drm: mediatek: remove clk_unprepare() in mtk_drm_crtc

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Date:   Wed, 29 May 2019 14:08:17 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     CK Hu <ck.hu@...iatek.com>
Cc:     "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Matthias Brugger <matthias.bgg@...il.com>,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] drm: mediatek: remove clk_unprepare() in mtk_drm_crtc_destroy()

On Wed, May 29, 2019 at 1:58 PM CK Hu <ck.hu@...iatek.com> wrote:
>
> Hi, Hsin-Yi:
>
> On Mon, 2019-05-27 at 12:50 +0800, Hsin-Yi Wang wrote:
> > There is no clk_prepare() called in mtk_drm_crtc_reset(), when unbinding
> > drm device, mtk_drm_crtc_destroy() will be triggered, and the clocks will
> > be disabled and unprepared in mtk_crtc_ddp_clk_disable. If clk_unprepare()
> > is called here, we'll get warnings[1], so remove clk_unprepare() here.
>
> In original code, clk_prepare() is called in mtk_drm_crtc_create() and
> clk_unprepare() is called in mtk_drm_crtc_destroy(). This looks correct.

clk_prepare() is removed in https://patchwork.kernel.org/patch/10872777/.

> I don't know why we should do any thing about clock in
> mtk_drm_crtc_reset(). To debug this, the first step is to print message
> when mediatek drm call clk_prepare() and clk_unprepare(). If these two
> interface is called in pair, I think we should not modify mediatek drm
> driver, the bug maybe in clock driver.
>