linux-kernel - Re: [PATCH v4 4/7] media: qcom: camss: Move VFE power-domain specifics into vfe.c

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Date:   Sat, 18 Nov 2023 01:32:31 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        hverkuil-cisco@...all.nl, laurent.pinchart@...asonboard.com,
        Robert Foss <rfoss@...nel.org>,
        Todor Tomov <todor.too@...il.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        matti.lehtimaki@...il.com, quic_grosikop@...cinc.com
Cc:     linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/7] media: qcom: camss: Move VFE power-domain
 specifics into vfe.c

On 3.11.2023 13:29, Bryan O'Donoghue wrote:
> Moving the location of the hooks to VFE power domains has several
> advantages.
> 
> 1. Separation of concerns and functional decomposition.
>    vfe.c should be responsible for and know best how manage
>    power-domains for a VFE, excising from camss.c follows this
>    principle.
> 
> 2. Embedding a pointer to genpd in struct camss_vfe{} meas that we can
>    dispense with a bunch of kmalloc array inside of camss.c.
> 
> 3. Splitting up titan top gdsc from vfe/ife gdsc provides a base for
>    breaking up magic indexes in dtsi.
> 
> Suggested-by: Matti Lehtimäki <matti.lehtimaki@...il.com>
> Tested-by: Matti Lehtimäki <matti.lehtimaki@...il.com>
> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> ---
[...]

> +/*
> + * msm_vfe_genpd_cleanup - Cleanup VFE genpd linkages
> + * @vfe: VFE device
You can even give this an upgrade to kerneldoc! :)

[...]

> +	/* count the # of VFEs which have flagged power-domain */
[...]

Personal peeve, but this comment seems a bit excessive

> +	for (vfepd_num = i = 0; i < camss->vfe_total_num; i++) {
> +		if (res->vfe_res[i].has_pd)
> +			vfepd_num++;
> +	}
>  
> -	camss->genpd_link = devm_kmalloc_array(dev, camss->genpd_num,
> -					       sizeof(*camss->genpd_link),
> -					       GFP_KERNEL);
> -	if (!camss->genpd_link)
> -		return -ENOMEM;
> +	/*
> +	 * If the number of power-domains is greater than the number of VFEs
> +	 * then the additional power-domain is for the entire CAMSS block the
> +	 * 'top' power-domain.
the last 3 words seem out of place

> +	 */
> +	if (camss->genpd_num <= vfepd_num)
> +		return 0;
if (!(camss->genpd_num > vfepd_num))

would probably be easier to follow given your comment above

Konrad