linux-kernel - Re: [PATCHv2] PCI: pciehp: Use appropriate conditions to check the hotplug controller status

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Date: Tue, 28 May 2024 13:54:01 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Bitao Hu <yaoma@...ux.alibaba.com>
cc: Lukas Wunner <lukas@...ner.de>, bhelgaas@...gle.com, 
    weirongguang@...inos.cn, linux-pci@...r.kernel.org, 
    LKML <linux-kernel@...r.kernel.org>, kanie@...ux.alibaba.com
Subject: Re: [PATCHv2] PCI: pciehp: Use appropriate conditions to check the
 hotplug controller status

On Tue, 28 May 2024, Bitao Hu wrote:

> "present" and "link_active" can be 1 if the status is ready, and 0 if
> it is not. Both of them can be -ENODEV if reading the config space
> of the hotplug port failed. That's typically the case if the hotplug
> port itself was hot-removed. Therefore, this situation can occur:
> pciehp_card_present() may return 1 and pciehp_check_link_active()
> may return -ENODEV because the hotplug port was hot-removed in-between
> the two function calls. In that case we'll emit both "Card present"
> *and* "Link Up" since both 1 and -ENODEV are considered "true". This
> is not the expected behavior. Those messages should be emited when
> "present" and "link_active" are positive.
> 
> Signed-off-by: Bitao Hu <yaoma@...ux.alibaba.com>
> Reviewed-by: Lukas Wunner <lukas@...ner.de>

Thanks for updaring the description.

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

-- 
 i.


> ---
> v1 -> v2:
> 1. Explain the rationale of the code change in the commit message
> more clearly.
> 2. Add the "Reviewed-by" tag of Lukas.
> ---
>  drivers/pci/hotplug/pciehp_ctrl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
> index dcdbfcf404dd..6adfdbb70150 100644
> --- a/drivers/pci/hotplug/pciehp_ctrl.c
> +++ b/drivers/pci/hotplug/pciehp_ctrl.c
> @@ -276,10 +276,10 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
>  	case OFF_STATE:
>  		ctrl->state = POWERON_STATE;
>  		mutex_unlock(&ctrl->state_lock);
> -		if (present)
> +		if (present > 0)
>  			ctrl_info(ctrl, "Slot(%s): Card present\n",
>  				  slot_name(ctrl));
> -		if (link_active)
> +		if (link_active > 0)
>  			ctrl_info(ctrl, "Slot(%s): Link Up\n",
>  				  slot_name(ctrl));
>  		ctrl->request_result = pciehp_enable_slot(ctrl);
>