Re: [PATCH v2 4/5] watchdog: rti_wdt: Add support for loading firmware

[Tom Rini <trini@konsulko.com>]

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On Sun, Jun 27, 2021 at 12:18:09PM -0600, Simon Glass wrote:
> Hi Jan,
> 
> On Sun, 27 Jun 2021 at 12:01, Jan Kiszka <jan.kiszka@siemens.com> wrote:
> >
> > On 26.06.21 20:29, Simon Glass wrote:
> > > Hi,
> > >
> > > On Fri, 11 Jun 2021 at 08:08, Tom Rini <trini@konsulko.com> wrote:
> > >>
> > >> On Fri, Jun 11, 2021 at 07:14:21PM +0530, Lokesh Vutla wrote:
> > >>> Hi Tom,
> > >>>
> > >>> On 09/06/21 6:47 pm, Jan Kiszka wrote:
> > >>>> On 07.06.21 13:44, Jan Kiszka wrote:
> > >>>>> On 07.06.21 13:40, Tom Rini wrote:
> > >>>>>> On Mon, Jun 07, 2021 at 03:33:52PM +0530, Lokesh Vutla wrote:
> > >>>>>>> +Tom,
> > >>>>>>>
> > >>>>>>> Hi Tom,
> > >>>>>>>
> > >>>>>>> On 02/06/21 3:07 pm, Jan Kiszka wrote:
> > >>>>>>>> From: Jan Kiszka <jan.kiszka@siemens.com>
> > >>>>>>>>
> > >>>>>>>> To avoid the need of extra boot scripting on AM65x for loading a
> > >>>>>>>> watchdog firmware, add the required rproc init and loading logic for the
> > >>>>>>>> first R5F core to the watchdog start handler. In case the R5F cluster is
> > >>>>>>>> in lock-step mode, also initialize the second core. The firmware itself
> > >>>>>>>> is embedded into U-Boot binary to ease access to it and ensure it is
> > >>>>>>>> properly hashed in case of secure boot.
> > >>>>>>>>
> > >>>>>>>> One possible firmware source is https://github.com/siemens/k3-rti-wdt.
> > >>>>>>>>
> > >>>>>>>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> > >>>>>>>> ---
> > >>>>>>>>  drivers/watchdog/Kconfig      | 20 ++++++++++++
> > >>>>>>>>  drivers/watchdog/Makefile     |  5 +++
> > >>>>>>>>  drivers/watchdog/rti_wdt.c    | 58 ++++++++++++++++++++++++++++++++++-
> > >>>>>>>>  drivers/watchdog/rti_wdt_fw.S | 20 ++++++++++++
> > >>>>>>>>  4 files changed, 102 insertions(+), 1 deletion(-)
> > >>>>>>>>  create mode 100644 drivers/watchdog/rti_wdt_fw.S
> > >>>>>>>>
> > >>>>>>>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> > >>>>>>>> index f0ff2612a6..1a1fddfe9f 100644
> > >>>>>>>> --- a/drivers/watchdog/Kconfig
> > >>>>>>>> +++ b/drivers/watchdog/Kconfig
> > >>>>>>>> @@ -209,6 +209,26 @@ config WDT_K3_RTI
> > >>>>>>>>           Say Y here if you want to include support for the K3 watchdog
> > >>>>>>>>           timer (RTI module) available in the K3 generation of processors.
> > >>>>>>>>
> > >>>>>>>> +if WDT_K3_RTI
> > >>>>>>>> +
> > >>>>>>>> +config WDT_K3_RTI_LOAD_FW
> > >>>>>>>> +       bool "Load watchdog firmware"
> > >>>>>>>> +       depends on REMOTEPROC
> > >>>>>>>> +       help
> > >>>>>>>> +         Automatically load the specified firmware image into the MCU R5F
> > >>>>>>>> +         core 0. On the AM65x, this firmware is supposed to handle the expiry
> > >>>>>>>> +         of the watchdog timer, typically by resetting the system.
> > >>>>>>>> +
> > >>>>>>>> +config WDT_K3_RTI_FW_FILE
> > >>>>>>>> +       string "Watchdog firmware image file"
> > >>>>>>>> +       default "k3-rti-wdt.fw"
> > >>>>>>>> +       depends on WDT_K3_RTI_LOAD_FW
> > >>>>>>>> +       help
> > >>>>>>>> +         Firmware image to be embedded into U-Boot and loaded on watchdog
> > >>>>>>>> +         start.
> > >>>>>>>
> > >>>>>>> I need your input on this proach. Is it okay to include the linker file unders
> > >>>>>>> drivers?
> > >>>>>>
> > >>>>>> Maybe?  I suppose the first thing that springs to mind is why aren't we
> > >>>>>> using binman and including this blob (which I happily see is GPLv2)
> > >>>>>> similar to how we do things with x86 for one example.
> > >>>>>>
> > >>>>>
> > >>>>> See https://www.mail-archive.com/u-boot@lists.denx.de/msg377894.html
> > >>>>>
> > >>>>> Jan
> > >>>>>
> > >>>>
> > >>>> Did this help to answer open questions? Otherwise, please let me know.
> > >>>>
> > >>>> I'd also like to avoid that his patch alone blocks 1-3 of the series
> > >>>> needless - but I would also not mind getting everything in at once.
> > >>>
> > >>> Can you provide your reviewed-by if you are okay with this approach?
> > >>
> > >> I was kind of hoping Simon would chime in here on binman usage.  So,
> > >> re-re-reading the above URL, yes, fsloader wouldn't be the right choice
> > >> for watchdog firmware.  But I think binman_entry_find() and related
> > >> could work, in general, for this case of "need firmware blob embedded in
> > >> to image".  That said, this isn't just any firmware blob, it's the
> > >> watchdog firmware.  The less reliance on other things the safer it is.
> > >> That means this would be an exception to the general firmware blob
> > >> loading rule and yeah, OK, we can do it this way.  Sorry for the delay.
> > >
> > > Yes I've been a little tied up recently. But I think this should use
> > > binman. We really don't want to be building binary firmware into
> > > U-Boot itself!
> > >
> > > Also Tom says, see x86 for a load of binaries of different types and
> > > how they are accessed at runttime. This is what binman is for.
> > >
> >
> > Please take the time and study my arguments. I'm open for better
> > proposals, but they need to be concrete and addressing my points.
> 
> Do you mean 'properly hashed' and 'easy access', or something else?
> What can binman not do?

Well, as I said when ack'ing this, we're also talking about making sure
the system watchdog works.  It needs to be as dead simple as possible.

-- 
Tom

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