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

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Date:   Wed, 6 Apr 2022 11:46:46 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     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:     shengjiu.wang@....com, cai.huoqing@...ux.dev, maxime@...no.tech,
        harry.wentland@....com, amuel@...lland.org
Subject: Re: [PATCH v1 1/5] drm: bridge: dw_hdmi: cec: Add cec suspend/resume
 function

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.

> +	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.

Regards,

	Hans

> +
> +	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);