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

[Jan Kiszka]

On 27.06.21 20:18, Simon Glass wrote:
> Hi Jan,
> 
> On Sun, 27 Jun 2021 at 12:01, Jan Kiszka <jan.kiszka at siemens.com> wrote:
>>
>> On 26.06.21 20:29, Simon Glass wrote:
>>> Hi,
>>>
>>> On Fri, 11 Jun 2021 at 08:08, Tom Rini <trini at 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 at 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 at 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?

Binman itself can stick things into binary images. But that is at most
half of the tasks needed here. I would need concrete guidance how to

 - access that binary from u-boot proper in a reasonably simple way
 - make sure the binary can be signed and the signature is evaluated
   before using it

Jan

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