linux-kernel - RE: [EXT] Re: [PATCH v1 1/5] drm: bridge: dw_hdmi: cec: Add cec suspend/resume function

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Date:   Thu, 7 Apr 2022 08:30:27 +0000
From:   Sandor Yu <sandor.yu@....com>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "andrzej.hajda@...el.com" <andrzej.hajda@...el.com>,
        "narmstrong@...libre.com" <narmstrong@...libre.com>,
        "robert.foss@...aro.org" <robert.foss@...aro.org>,
        "Laurent.pinchart@...asonboard.com" 
        <Laurent.pinchart@...asonboard.com>,
        "jonas@...boo.se" <jonas@...boo.se>,
        "jernej.skrabec@...il.com" <jernej.skrabec@...il.com>
CC:     "S.J. Wang" <shengjiu.wang@....com>,
        "cai.huoqing@...ux.dev" <cai.huoqing@...ux.dev>,
        "maxime@...no.tech" <maxime@...no.tech>,
        "harry.wentland@....com" <harry.wentland@....com>,
        "amuel@...lland.org" <amuel@...lland.org>
Subject: RE: [EXT] Re: [PATCH v1 1/5] drm: bridge: dw_hdmi: cec: Add cec
 suspend/resume function

Hi,

> -----Original Message-----
> From: Hans Verkuil <hverkuil-cisco@...all.nl>
> Sent: 2022年4月6日 17:47
> To: Sandor Yu <sandor.yu@....com>; dri-devel@...ts.freedesktop.org;
> linux-kernel@...r.kernel.org; andrzej.hajda@...el.com;
> narmstrong@...libre.com; robert.foss@...aro.org;
> Laurent.pinchart@...asonboard.com; jonas@...boo.se;
> jernej.skrabec@...il.com
> Cc: S.J. Wang <shengjiu.wang@....com>; cai.huoqing@...ux.dev;
> maxime@...no.tech; harry.wentland@....com; amuel@...lland.org
> Subject: [EXT] Re: [PATCH v1 1/5] drm: bridge: dw_hdmi: cec: Add cec
> suspend/resume function
> 
> Caution: EXT Email
> 
> Hi Sandor,
> 
> On 06/04/2022 10:48, Sandor.yu@....com wrote:
> > From: Sandor Yu <Sandor.yu@....com>
> >
> > CEC interrupt status/mask and logical address registers will be reset
> > when device enter suspend.
> > It will cause cec fail to work after device resume.
> > Add CEC suspend/resume functions, save these registers status when
> > suspend and restore them when resume.
> >
> > Signed-off-by: Sandor Yu <Sandor.yu@....com>
> > ---
> >  drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c | 35
> > +++++++++++++++++++
> >  1 file changed, 35 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c
> > b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c
> > index c8f44bcb298a..ceb619b32fde 100644
> > --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c
> > +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c
> > @@ -18,6 +18,8 @@
> >
> >  #include "dw-hdmi-cec.h"
> >
> > +static u8 cec_saved_regs[5];
> 
> Ewww, not a global. Just save it in struct dw_hdmi_cec.

> 
> > +
> >  enum {
> >       HDMI_IH_CEC_STAT0       = 0x0106,
> >       HDMI_IH_MUTE_CEC_STAT0  = 0x0186, @@ -306,11 +308,44
> @@ static
> > int dw_hdmi_cec_remove(struct platform_device *pdev)
> >       return 0;
> >  }
> >
> > +static int __maybe_unused dw_hdmi_cec_resume(struct device *dev) {
> > +     struct dw_hdmi_cec *cec = dev_get_drvdata(dev);
> > +
> > +     /* Restore logical address and interrupt status/mask register */
> > +     dw_hdmi_write(cec, cec_saved_regs[0], HDMI_CEC_ADDR_L);
> > +     dw_hdmi_write(cec, cec_saved_regs[1], HDMI_CEC_ADDR_H);
> 
> No need to store HDMI_CEC_ADDR_L/R, just use cec->addresses.
Agree, I will use it later.
> 
> > +     dw_hdmi_write(cec, cec_saved_regs[2], HDMI_CEC_POLARITY);
> > +     dw_hdmi_write(cec, cec_saved_regs[3], HDMI_CEC_MASK);
> > +     dw_hdmi_write(cec, cec_saved_regs[4],
> HDMI_IH_MUTE_CEC_STAT0);
> 
> This doesn't call cec->ops->disable/enable. It might be better to just call
> dw_hdmi_cec_enable() and store the enable state in struct dw_hdmi_cec.
If call cec->ops->disable/enable in suspend/resume, CEC stack will be reset.
CEC user such as EARC/ARC, the CEC link is expect keep in active after device resume.
So I prefer only save those registers for better user experience.
> 
> Regards,
> 
>         Hans
> 
Thanks
Sandor
> > +
> > +     return 0;
> > +}
> > +
> > +static int __maybe_unused dw_hdmi_cec_suspend(struct device *dev) {
> > +     struct dw_hdmi_cec *cec = dev_get_drvdata(dev);
> > +
> > +     /* store logical address and interrupt status/mask register */
> > +     cec_saved_regs[0] = dw_hdmi_read(cec, HDMI_CEC_ADDR_L);
> > +     cec_saved_regs[1] = dw_hdmi_read(cec, HDMI_CEC_ADDR_H);
> > +     cec_saved_regs[2] = dw_hdmi_read(cec, HDMI_CEC_POLARITY);
> > +     cec_saved_regs[3] = dw_hdmi_read(cec, HDMI_CEC_MASK);
> > +     cec_saved_regs[4] = dw_hdmi_read(cec,
> HDMI_IH_MUTE_CEC_STAT0);
> > +
> > +     return 0;
> > +}
> > +
> > +static const struct dev_pm_ops dw_hdmi_cec_pm = {
> > +     SET_SYSTEM_SLEEP_PM_OPS(dw_hdmi_cec_suspend,
> dw_hdmi_cec_resume)
> > +};
> > +
> >  static struct platform_driver dw_hdmi_cec_driver = {
> >       .probe  = dw_hdmi_cec_probe,
> >       .remove = dw_hdmi_cec_remove,
> >       .driver = {
> >               .name = "dw-hdmi-cec",
> > +             .pm = &dw_hdmi_cec_pm,
> >       },
> >  };
> >  module_platform_driver(dw_hdmi_cec_driver);