linux-kernel - Re: [PATCH v2 3/3] media: camss: Link CAMSS power domain

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Message-ID: <fa395680-0e6c-3eb0-9d5a-f90a95c394b8@linaro.org>
Date:   Fri, 26 May 2023 21:49:30 +0100
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Yassine Oudjana <yassine.oudjana@...il.com>,
        Robert Foss <rfoss@...nel.org>,
        Todor Tomov <todor.too@...il.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Hans Verkuil <hansverk@...co.com>
Cc:     Yassine Oudjana <y.oudjana@...tonmail.com>,
        Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>,
        linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] media: camss: Link CAMSS power domain

On 26/05/2023 19:07, Yassine Oudjana wrote:
> From: Yassine Oudjana <y.oudjana@...tonmail.com>
> 
> The CAMSS power domain was previously enabled implicitly when the VFE
> power domains were enabled.
> Commit 46cc03175498 ("media: camss: Split power domain management")
> delayed enabling VFE power domains which in turn delayed enabling the
> CAMSS power domain. This made CSIPHY fail to enable camss_top_ahb_clk
> which requires the CAMSS power domain to be on:
> 
> [  199.097810] ------------[ cut here ]------------
> [  199.097893] camss_top_ahb_clk status stuck at 'off'
> [  199.097913] WARNING: CPU: 3 PID: 728 at drivers/clk/qcom/clk-branch.c:91 clk_branch_wait+0x140/0x160
> ...
> [  199.100064]  clk_branch_wait+0x140/0x160
> [  199.100112]  clk_branch2_enable+0x30/0x40
> [  199.100159]  clk_core_enable+0x6c/0xb0
> [  199.100211]  clk_enable+0x2c/0x50
> [  199.100257]  camss_enable_clocks+0x94/0xe0 [qcom_camss]
> [  199.100342]  csiphy_set_power+0x154/0x2a0 [qcom_camss]
> ...
> [  199.101594] ---[ end trace 0000000000000000 ]---
> 
> Link the CAMSS power domain in camss_configure_pd to make sure it gets
> enabled before CSIPHY tries to enable clocks.
> 
> Fixes: 02afa816dbbf ("media: camss: Add basic runtime PM support")
> Signed-off-by: Yassine Oudjana <y.oudjana@...tonmail.com>
> ---
>   drivers/media/platform/qcom/camss/camss.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
> index 1ef26aea3eae..9aea8220d923 100644
> --- a/drivers/media/platform/qcom/camss/camss.c
> +++ b/drivers/media/platform/qcom/camss/camss.c
> @@ -1453,6 +1453,7 @@ static const struct media_device_ops camss_media_ops = {
>   static int camss_configure_pd(struct camss *camss)
>   {
>   	struct device *dev = camss->dev;
> +	int camss_pd_index;
>   	int i;
>   	int ret;
>   
> @@ -1496,7 +1497,13 @@ static int camss_configure_pd(struct camss *camss)
>   		}
>   	}
>   
> -	if (i > camss->vfe_num) {
> +	/* Link CAMSS power domain if available */
> +	camss_pd_index = device_property_match_string(camss->dev, "power-domain-names", "camss");
> +	if (camss_pd_index >= 0)
> +		device_link_add(camss->dev, camss->genpd[camss_pd_index], DL_FLAG_STATELESS |
> +				DL_FLAG_PM_RUNTIME | DL_FLAG_RPM_ACTIVE);
> +
> +	if (i > camss->vfe_num && i != camss_pd_index) {
>   		camss->genpd_link[i - 1] = device_link_add(camss->dev, camss->genpd[i - 1],
>   							   DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME |
>   							   DL_FLAG_RPM_ACTIVE);

Konrad pointed this out.

Are you 100% sure you want to do this. We already have a way to count 
the # of power-domains in camss_configure_pd().

Your series is now adding a dependency on power-domain-names.

Is there a good reason to add that dependency ? If not, then lets just 
take the code from camss_configure_pd() and make it so that it can be 
used/reused here.

---
bod