linux-kernel - Re: [PATCH] interconnect: Restore sync state by ignoring ipa-virt in provider count

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Date:   Wed, 27 Apr 2022 07:00:40 -0500
From:   Alex Elder <elder@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>,
        Georgi Djakov <djakov@...nel.org>
Cc:     linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Doug Anderson <dianders@...omium.org>,
        Taniya Das <quic_tdas@...cinc.com>,
        Mike Tipton <quic_mdtipton@...cinc.com>
Subject: Re: [PATCH] interconnect: Restore sync state by ignoring ipa-virt in
 provider count

On 4/26/22 8:32 PM, Stephen Boyd wrote:
> Ignore compatible strings for the IPA virt drivers that were removed in
> commits 2fb251c26560 ("interconnect: qcom: sdx55: Drop IP0
> interconnects") and 2f3724930eb4 ("interconnect: qcom: sc7180: Drop IP0
> interconnects") so that the sync state logic can kick in again.
> Otherwise all the interconnects in the system will stay pegged at max
> speeds because 'providers_count' is always going to be one larger than
> the number of drivers that will ever probe on sc7180 or sdx55. This
> fixes suspend on sc7180 and sdx55 devices when you don't have a
> devicetree patch to remove the ipa-virt compatible node.
> 
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> Cc: Doug Anderson <dianders@...omium.org>
> Cc: Alex Elder <elder@...aro.org>
> Cc: Taniya Das <quic_tdas@...cinc.com>
> Cc: Mike Tipton <quic_mdtipton@...cinc.com>
> Fixes: 2fb251c26560 ("interconnect: qcom: sdx55: Drop IP0 interconnects")
> Fixes: 2f3724930eb4 ("interconnect: qcom: sc7180: Drop IP0 interconnects")
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>

So of_count_icc_providers() counts the number of
interconnect providers defined in the DTB, regardless
of whether anything in the code supports it.

This seems to be a more general problem, but I
suppose in practice it's not likely to occur.

I think your solution looks fine, but I'm interested
in what Georgi has to say.

Reviewed-by: Alex Elder <elder@...aro.org>


> ---
>   drivers/interconnect/core.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
> index 9050ca1f4285..c52915a58b22 100644
> --- a/drivers/interconnect/core.c
> +++ b/drivers/interconnect/core.c
> @@ -1087,9 +1087,15 @@ static int of_count_icc_providers(struct device_node *np)
>   {
>   	struct device_node *child;
>   	int count = 0;
> +	const struct of_device_id ignore_list[] = {
> +		{ .compatible = "qcom,sc7180-ipa-virt" },
> +		{ .compatible = "qcom,sdx55-ipa-virt" },
> +		{}
> +	};
>   
>   	for_each_available_child_of_node(np, child) {
> -		if (of_property_read_bool(child, "#interconnect-cells"))
> +		if (of_property_read_bool(child, "#interconnect-cells") &&
> +		    likely(!of_match_node(ignore_list, child)))
>   			count++;
>   		count += of_count_icc_providers(child);
>   	}
> 
> base-commit: 2fb251c265608636fc961b7d38e1a03937e57371