Re: [PATCH] remoteproc: zynqmp: Add coredump support

From: Mathieu Poirier <mathieu.poirier@linaro.org>
To: Leonard Crestez <cdleonard@gmail.com>
Cc: Tanmay Shah <tanmay.shah@amd.com>,
	Bjorn Andersson <andersson@kernel.org>,
	Michal Simek <michal.simek@amd.com>,
	linux-remoteproc@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] remoteproc: zynqmp: Add coredump support
Date: Thu, 28 Mar 2024 08:53:06 -0600	[thread overview]
Message-ID: <ZgWEUpgmPPfFAjo/@p14s> (raw)
In-Reply-To: <07183fd8-a5a1-4cae-b317-d703ef7c1de1@gmail.com>

On Thu, Mar 28, 2024 at 10:17:13AM +0200, Leonard Crestez wrote:
> On 3/18/24 18:52, Mathieu Poirier wrote:
> > Hi Leonard,
> > 
> > I have queued patches for this driver that will break this patch.  Please
> > re-submit when v6.9-rc1 is out and rproc-next has been updated, which should be
> > around the middle of next week.
> 
> Hello,
> 
> It's been a while - v6.9-rc1 is out and rproc-next has been rebased on top of
> it. But the coredump patch still applies? I expected some unrelated
> xlnx_r5_remoteproc patches to cause conflicts but there's nothing there.
> 
> It seems to me that the patch can be applied as-is and no resend is required.
> Am I missing something?
>

You're not missing anything.  Back when I wrote my initial comment Tanmay had
submitted patches to fix the way TCMs are initialized, which conflicted with
your patch.  There were some last minute modifications to Tanmay's patchset and
I ended up not applying it, leading us to where we are today.

Tanmay - please review and test this patch.

Thanks,
Mathieu

> --
> Regards,
> Leonard
> 
> > On Sat, Mar 16, 2024 at 08:16:42PM +0200, Leonard Crestez wrote:
> >> Supporting remoteproc coredump requires the platform-specific driver to
> >> register coredump segments to be dumped. Do this by calling
> >> rproc_coredump_add_segment for every carveout.
> >>
> >> Also call rproc_coredump_set_elf_info when then rproc is created. If the
> >> ELFCLASS parameter is not provided then coredump fails with an error.
> >> Other drivers seem to pass EM_NONE for the machine argument but for me
> >> this shows a warning in gdb. Pass EM_ARM because this is an ARM R5.
> >>
> >> Signed-off-by: Leonard Crestez <cdleonard@gmail.com>
> >> ---
> >>
> >> Tests were done by triggering an deliberate crash using remoteproc
> >> debugfs: echo 2 > /sys/kernel/debug/remoteproc/remoteproc0/crash
> >>
> >> This was tested using RPU apps which use RAM for everything so TCM dump
> >> was not verified. The freertos-gdb script package showed credible data:
> >>
> >> https://github.com/espressif/freertos-gdb
> >>
> >> The R5 cache is not flushed so RAM might be out of date which is
> >> actually very bad because information most relevant to determining the
> >> cause of a crash is lost. Possible workaround would be to flush caches
> >> in some sort of R5 crash handler? I don't think Linux can do anything
> >> about this limitation.
> >>
> >> The generated coredump doesn't contain registers, this seems to be a
> >> limitation shared with other rproc coredumps. It's not clear how the apu
> >> could access rpu registers on zynqmp, my only idea would be to use the
> >> coresight dap but that sounds difficult.