From: Michael Ellerman <mpe@ellerman•id.au>
To: "Guilherme G. Piccoli" <gpiccoli@linux•vnet.ibm.com>,
linuxppc-dev@lists•ozlabs.org, linux-kernel@vger•kernel.org
Cc: gpiccoli@linux•vnet.ibm.com, benh@kernel•crashing.org,
paulus@samba•org, maurosr@linux•vnet.ibm.com
Subject: Re: [PATCH] powerpc/powernv: Enable reset_devices parameter to issue a PHB reset
Date: Fri, 13 Oct 2017 19:37:27 +1100 [thread overview]
Message-ID: <87fuantpdk.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20171012222153.24905-1-gpiccoli@linux.vnet.ibm.com>
"Guilherme G. Piccoli" <gpiccoli@linux•vnet.ibm.com> writes:
> During a kdump kernel boot in PowerPC, we request a reset of the
> PHBs to the FW. It makes sense, since if we are booting a kdump
> kernel it means we had some trouble before and we cannot rely in
> the adapters' health; they could be in a bad state, hence the
> reset is needed.
>
> But not only in a kdump kernel we could use this reset - there are
> situations, specially when debugging drivers, that we could break
> an adapter in a way it requires such reset. One can tell to just
> go ahead and reboot the machine, but happens that many times doing
> kexec is much faster, and so preferable than a full power cycle.
> Also, we could have situations in which adapters are in bad state
> due to adapter's FW issue, and only a PHB Fundamental Reset could
> revive them.
>
> This patch enables the reset_devices parameter to perform such reset.
> The parameter is barely used - only few drivers make use of it.
> This is a PowerPC-only change.
>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux•vnet.ibm.com>
> ---
> This patch was built/tested against powerpc/next branch.
>
> We recently had a situation in which i40e driver couldn't start,
> even after a full power cycle, due to a bug in its FW triggered
> by a DCB condition in switch (thanks Mauro for narrowing this).
> This patch enabled us to revive the adapter and use network
> while debugging.
I really dislike this.
You're basically saying the kernel can't work out how to get a device
working, so let's leave it up to the user.
The driver should be fixed to detect that the device is not responding
and request a reset.
cheers
next prev parent reply other threads:[~2017-10-13 8:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-12 22:21 [PATCH] powerpc/powernv: Enable reset_devices parameter to issue a PHB reset Guilherme G. Piccoli
2017-10-13 8:37 ` Michael Ellerman [this message]
2017-10-13 13:02 ` Guilherme G. Piccoli
2017-10-14 9:13 ` Benjamin Herrenschmidt
2017-10-15 21:51 ` Guilherme G. Piccoli
2017-10-25 15:30 ` Guilherme G. Piccoli
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