netdev - Re: [PATCH/RFC net] net: dec: tulip: de2104x: Add shutdown handler to stop NIC

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Date:   Thu, 22 Oct 2020 16:04:16 -0700
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     Moritz Fischer <mdf@...nel.org>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, linux-parisc@...r.kernel.org,
        linux-kernel@...r.kernel.org, lucyyan@...gle.com
Subject: Re: [PATCH/RFC net] net: dec: tulip: de2104x: Add shutdown handler
 to stop NIC

On Thu, 2020-10-22 at 15:06 -0700, Moritz Fischer wrote:
> The driver does not implement a shutdown handler which leads to
> issues
> when using kexec in certain scenarios. The NIC keeps on fetching
> descriptors which gets flagged by the IOMMU with errors like this:
> 
> DMAR: DMAR:[DMA read] Request device [5e:00.0]fault addr fffff000
> DMAR: DMAR:[DMA read] Request device [5e:00.0]fault addr fffff000
> DMAR: DMAR:[DMA read] Request device [5e:00.0]fault addr fffff000
> DMAR: DMAR:[DMA read] Request device [5e:00.0]fault addr fffff000
> DMAR: DMAR:[DMA read] Request device [5e:00.0]fault addr fffff000
> 
> Signed-off-by: Moritz Fischer <mdf@...nel.org>
> ---
> 
> Hi all,
> 
> I'm not sure if this is the proper way for a shutdown handler,
> I've tried to look at a bunch of examples and couldn't find a
> specific
> solution, in my tests on hardware this works, though.
> 
> Open to suggestions.
> 
> Thanks,
> Moritz
> 
> ---
>  drivers/net/ethernet/dec/tulip/de2104x.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/dec/tulip/de2104x.c
> b/drivers/net/ethernet/dec/tulip/de2104x.c
> index f1a2da15dd0a..372c62c7e60f 100644
> --- a/drivers/net/ethernet/dec/tulip/de2104x.c
> +++ b/drivers/net/ethernet/dec/tulip/de2104x.c
> @@ -2185,6 +2185,7 @@ static struct pci_driver de_driver = {
>  	.id_table	= de_pci_tbl,
>  	.probe		= de_init_one,
>  	.remove		= de_remove_one,
> +	.shutdown	= de_remove_one,

This doesn't look right: shutdown is supposed to turn off the device
without disturbing the tree or causing any knock on effects (I think
that rule is mostly because you don't want anything in userspace
triggering since it's likely to be nearly dead).  Remove removes the
device from the tree and cleans up everything.  I think the function
you want that's closest to what shutdown needs is de_close().  That
basically just turns off the chip and frees the interrupt ... you'll
have to wrapper it to call it from the pci_driver, though.

James