linux-kernel - Re: [PATCH RESEND] PCI: endpoint: Fix clearing start entry in configfs

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Message-ID: <20200221141553.GA15440@e121166-lin.cambridge.arm.com>
Date:   Fri, 21 Feb 2020 14:15:53 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Kishon Vijay Abraham I <kishon@...com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] PCI: endpoint: Fix clearing start entry in
 configfs

On Fri, Dec 20, 2019 at 09:24:37PM +0900, Kunihiko Hayashi wrote:
> The value of 'start' entry is no change whenever writing 0 to configfs.
> So the endpoint that stopped once can't restart.
> 
> The following command lines are an example restarting endpoint and
> reprogramming configurations after receiving bus-reset.
> 
>     echo 0 > controllers/66000000.pcie-ep/start
>     rm controllers/66000000.pcie-ep/func1
>     ln -s functions/pci_epf_test/func1 controllers/66000000.pcie-ep/
>     echo 1 > controllers/66000000.pcie-ep/start
> 
> However, the first 'echo' can't set 0 to 'start', so the last 'echo' can't
> restart endpoint.

I think your description is not correct - pci_epc_group->start is
just used to check if an endpoint has been started or not (in
pci_epc_epf_unlink() and that's a WARN_ON) but nonetheless this
looks like a bug and ought to be fixed.

I need Kishon's ACK to proceed.

Thanks,
Lorenzo

> Fixes: d74679911610 ("PCI: endpoint: Introduce configfs entry for configuring EP functions")
> Cc: Kishon Vijay Abraham I <kishon@...com>
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
> ---
>  drivers/pci/endpoint/pci-ep-cfs.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c
> index d1288a0..4fead88 100644
> --- a/drivers/pci/endpoint/pci-ep-cfs.c
> +++ b/drivers/pci/endpoint/pci-ep-cfs.c
> @@ -58,6 +58,7 @@ static ssize_t pci_epc_start_store(struct config_item *item, const char *page,
>  
>  	if (!start) {
>  		pci_epc_stop(epc);
> +		epc_group->start = 0;
>  		return len;
>  	}
>  
> -- 
> 2.7.4
>