linux-kernel - RE: [PATCH v10 5/5] drm/rockchip: Add dmc notifier in vop driver

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Date:   Tue, 06 Sep 2016 04:37:54 +0000
From:   MyungJoo Ham <myungjoo.ham@...sung.com>
To:     Lin Huang <hl@...k-chips.com>,
        heiko@...ech.de <heiko@...ech.de>
Cc:     mark.yao@...k-chips.com 
        <mark.yao@...k-chips.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        airlied@...ux.ie <airlied@...ux.ie>,
        mturquette@...libre.com 
        <mturquette@...libre.com>,
        dbasehore@...omium.org 
        <dbasehore@...omium.org>,
        sboyd@...eaurora.org <sboyd@...eaurora.org>,
        linux-kernel@...r.kernel.org 
        <linux-kernel@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org 
        <dri-devel@...ts.freedesktop.org>,
        dianders@...omium.org <dianders@...omium.org>,
        linux-rockchip@...ts.infradead.org 
        <linux-rockchip@...ts.infradead.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        linux-arm-kernel@...ts.infradead.org 
        <linux-arm-kernel@...ts.infradead.org>,
        tixy@...aro.org <tixy@...aro.org>,
        typ@...k-chips.com <typ@...k-chips.com>,
        sudeep.holla@....com <sudeep.holla@....com>,
        mark.rutland@....com <mark.rutland@....com>,
        linux-pm@...r.kernel.org 
        <linux-pm@...r.kernel.org>,
        devicetree@...r.kernel.org 
        <devicetree@...r.kernel.org>
Subject: RE: [PATCH v10 5/5] drm/rockchip: Add dmc notifier in vop driver

> when in ddr frequency scaling process, vop can not do enable or
> disable operation, since in dcf we check vop clock to see whether
> vop work. If vop work, dcf do ddr frequency scaling when vop
> in vblank status, and we need to read vop register to check whether
> vop go into vblank status. If vop not work, dcf can do ddr frequency
> any time. So when do ddr frequency scaling, you disabled or enable
> vop, there may two bad thing happen: 1, the panel flicker(when vop from
> disable status change to enable). 2, kernel hang (when vop from enable
> status change to disable, dcf need to read vblank status, but if you disable
> vop clock, it can not get the status, it will lead soc dead) So we need
> register to devfreq notifier, and we can get the dmc status. Also, when
> there have two vop enabled, we need to disable dmc, since dcf only base
> on one vop vblank time, so the other panel will flicker when do ddr
> frequency scaling.
> 
> Signed-off-by: Lin Huang <hl@...k-chips.com>
> Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>


Acked-by: MyungJoo Ham <myungjoo.ham@...sung.com>


The code looks fine, but I've just found that I cannot merge this
code as I am not handling drivers/gpu/drm.

Please try to merge this piece into drivers/gpu/drm tree.

For the other 4 piecies (1/5 to 4/5) I'm ok with them. I'm merging them now.


> ---
> Changes in v10:
> - None
> 
> Changes in v9:
> - None
> 
> Changes in v8:
> - None
> 
> Changes in v7:
> - None
> 
> Changes in v6:
> - fix a build error
> 
> Changes in v5:
> - improve some nits
> 
> Changes in v4:
> - register notifier to devfreq_register_notifier
> - use DEVFREQ_PRECHANGE and DEVFREQ_POSTCHANGE to get dmc status
> - when two vop enable, disable dmc
> - when two vop back to one vop, enable dmc
> 
> Changes in v3:
> - when do vop eanble/disable, dmc will wait until it finish
> 
> Changes in v2:
> - None
> 
> Changes in v1:
> - use wait_event instead usleep
> 
>  drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 116 ++++++++++++++++++++++++++++
>  1 file changed, 116 insertions(+)
>