linux-kernel - Re: [PATCH v3 07/15] media: qcom: camss: Capture VFE CSID dependency in a helper function

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Message-ID: <20230828184716.GM14596@pendragon.ideasonboard.com>
Date:   Mon, 28 Aug 2023 21:47:16 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Cc:     rfoss@...nel.org, todor.too@...il.com, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org, mchehab@...nel.org,
        hverkuil-cisco@...all.nl, sakari.ailus@...ux.intel.com,
        andrey.konovalov@...aro.org, linux-media@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 07/15] media: qcom: camss: Capture VFE CSID dependency
 in a helper function

Hi Bryan,

Thank you for the patch.

On Wed, Aug 23, 2023 at 11:44:36AM +0100, Bryan O'Donoghue wrote:
> From sdm845 onwards we need to ensure the VFE is powered on prior to
> switching on the CSID.

Based on the discussions with Konrad in the mail thread, I would record
here the reason for this requirement.

What happens if you unconditionally power up the VFE prior to switching
the CSID on ? Will this break something on platforms older than SDM845 ?

> Alternatively we could model up the GDSCs and clocks the CSID needs
> without the VFE but, there's a real question of the legitimacy of such a
> use-case.
> 
> For now drawing a line at sdm845 and switching on the associated VFEs is
> a perfectly valid thing to do.
> 
> Rather than continually extend out this clause for at least two new SoCs
> with this same model - making the vfe_get/vfe_put path start to look
> like spaghetti we can encoded the dependency in a helper function.
> 
> Use csid_depends_vfe() for this purpose.
> 
> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> ---
>  .../media/platform/qcom/camss/camss-csid.c    | 20 +++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/camss/camss-csid.c b/drivers/media/platform/qcom/camss/camss-csid.c
> index 08991b070bd61..fd04ed112b564 100644
> --- a/drivers/media/platform/qcom/camss/camss-csid.c
> +++ b/drivers/media/platform/qcom/camss/camss-csid.c
> @@ -146,6 +146,22 @@ static int csid_set_clock_rates(struct csid_device *csid)
>  	return 0;
>  }
>  
> +static bool csid_depends_vfe(u32 version)
> +{
> +	bool ret = false;
> +
> +	switch (version) {
> +	case CAMSS_845:
> +	case CAMSS_8250:
> +		ret = true;
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
>  /*
>   * csid_set_power - Power on/off CSID module
>   * @sd: CSID V4L2 subdevice
> @@ -163,7 +179,7 @@ static int csid_set_power(struct v4l2_subdev *sd, int on)
>  	int ret = 0;
>  
>  	if (on) {
> -		if (version == CAMSS_8250 || version == CAMSS_845) {
> +		if (csid_depends_vfe(version)) {
>  			ret = vfe_get(vfe);
>  			if (ret < 0)
>  				return ret;
> @@ -217,7 +233,7 @@ static int csid_set_power(struct v4l2_subdev *sd, int on)
>  		regulator_bulk_disable(csid->num_supplies,
>  				       csid->supplies);
>  		pm_runtime_put_sync(dev);
> -		if (version == CAMSS_8250 || version == CAMSS_845)
> +		if (csid_depends_vfe(version))
>  			vfe_put(vfe);
>  	}
>  

-- 
Regards,

Laurent Pinchart