linux-kernel - Re: [PATCH v2] spmi: Fix controller->node != parent->node breakage

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Message-ID: <91e2bd5b-71fa-402a-82cb-e68d3295804a@gmail.com>
Date: Tue, 14 Jan 2025 21:37:20 +0100
From: Konrad Dybcio <konradybcio@...il.com>
To: Stephen Boyd <sboyd@...nel.org>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Joe Hattori <joe@...is.s.u-tokyo.ac.jp>,
 Konrad Dybcio <konradybcio@...nel.org>,
 Matthias Brugger <matthias.bgg@...il.com>,
 Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>,
 linux-kernel@...r.kernel.org,
 Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
 Abel Vesa <abel.vesa@...aro.org>, Johan Hovold <johan+linaro@...nel.org>,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
 Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH v2] spmi: Fix controller->node != parent->node breakage



On 1/14/25 19:30, Stephen Boyd wrote:
> Quoting Konrad Dybcio (2025-01-13 14:12:28)
>>
>> On 1/13/25 22:52, Stephen Boyd wrote:
>>> Quoting Konrad Dybcio (2025-01-13 05:02:58)
>>>>
>>>> Make controller->node specifiable to both benefit from Joe's refcount
>>>> improvements and un-break the aforementioned platforms.
>>>
>>> How is it broken? I see spmi_pmic_arb_bus_init() calls
>>> devm_spmi_controller_alloc() which sets the of_node to the parent device
>>> and then spmi_pmic_arb_bus_init() overwrites that with
>>> 'ctrl->dev.of_node = node' later on in the same function. That will
>>> cause one more of_node_put() than is expected. I don't see that removed
>>> in this patch though, so the leak is still there?
>>>
>>>>
>>>> Fixes: 821b07853e32 ("spmi: hisi-spmi-controller: manage the OF node reference in device initialization and cleanup")
>>>
>>> I've dropped this patch from my queue. I don't know if we're really
>>> doing anything better by managing the of_node lifetime in that function
>>> vs. letting the callers assign the node they want and manage the
>>> lifetime themselves. Maybe we don't need to do anything? Presumably the
>>> parent device driver will unregister the controller anyway, so the
>>> lifetime of the of_node will be ensured regardless. For subnodes like
>>> qcom SPMI, the subnodes are child nodes of the parent device so they
>>> won't be removed. If they are dynamic nodes, then the caller can manage
>>> the lifetime.
>>
>> Stephen, the wrong node gets assigned in the qcom driver with
>> multi-master controllers, resulting in probe failures.
>>
>> Since the introduction of the commit referenced in fixes,
>> of_spmi_register_devices() sees the controller's subnodes
>> (which describe each of the two masters) as slave devices
>> - meaning no "real" devices ever get to probe
>>
> 
> Ok, I see that I was reading the already reverted state of the tree
> where the 'ctrl->dev.of_node = node' assignment came back. So there's
> nothing to do besides drop the patch in fixes, which I already did. We
> can then apply this patch to drop the duplicate assignment as a cleanup
> and to avoid a refcount bump on the of_node that isn't needed.
> 
> ----8<---
> diff --git a/drivers/spmi/hisi-spmi-controller.c b/drivers/spmi/hisi-spmi-controller.c
> index 3cafdf22c909..122140b97579 100644
> --- a/drivers/spmi/hisi-spmi-controller.c
> +++ b/drivers/spmi/hisi-spmi-controller.c
> @@ -300,9 +300,6 @@ static int spmi_controller_probe(struct platform_device *pdev)
>   
>   	spin_lock_init(&spmi_controller->lock);
>   
> -	ctrl->dev.parent = pdev->dev.parent;
> -	ctrl->dev.of_node = of_node_get(pdev->dev.of_node);
> -
>   	/* Callbacks */
>   	ctrl->read_cmd = spmi_read_cmd;
>   	ctrl->write_cmd = spmi_write_cmd;

That works for me, thank you

Konrad