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

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Message-ID: <a84f33f5-cf46-48ef-a9a9-01acb926c145@linaro.org>
Date:   Sat, 26 Aug 2023 12:02:02 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>, rfoss@...nel.org,
        todor.too@...il.com, agross@...nel.org, andersson@...nel.org,
        mchehab@...nel.org, hverkuil-cisco@...all.nl,
        laurent.pinchart@...asonboard.com, sakari.ailus@...ux.intel.com,
        andrey.konovalov@...aro.org
Cc:     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

On 23.08.2023 12:44, Bryan O'Donoghue wrote:
> From sdm845 onwards we need to ensure the VFE is powered on prior to
> switching on the CSID.
And what's the symptom if we fail to ensure this? How can someone
adding support for another platform tell whether the match-list
should be expanded?

> 
> 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)
toggle_vfe_before_csid?

> +{
> +	bool ret = false;
> +
> +	switch (version) {
> +	case CAMSS_845:
> +	case CAMSS_8250:
> +		ret = true;
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return ret;
I'm not sure if it would be okay with like C conventions and
stuff, but this can be made shorter by returning from within
the switch statement

Konrad