Re: [PATCH v2 2/3] rtc: rx6110: add ACPI bindings to I2C

Andy Shevchenko
2020-11-17T11:34:01Z

On Tue, Nov 17, 2020 at 11:51 AM johannes-hahn@siemens.com
<johannes-hahn@siemens.com> wrote:
>
> Hello Val,
>
> my name is Johannes Hahn from Siemens AG in Germany.
> Our product Open Controller II (OCII)[1] uses the Realtime Clock RX6110SA from SEIKO EPSON.

Nice to hear from you!

> Currently there is a merge request ongoing for the Linux Kernel master branch[2] which adds I²C and ACPI support to your original driver implementation.
>
> Simultaneously there is an already merged patch-set for coreboot[3] available creating the ACPI (SSDT) table entries for the RX6110SA.

Thanks for pointers, I commented there. The ACPI ID change must be reverted!

> The OCII uses coreboot for firmware initialization.
>
> During the merge request the eligible objection arose that the ACPI ID used in the Linux driver patch is not conforming the ACPI Specification.
> Indeed it does not. But when searching for a product identifier of RX6110SA I was not able to find a sufficient one with respect to the ACPI Specification (see [4] chapter 6.1.5 _HID (Hardware ID),[5]).

Unfortunately many vendors, even being registered in the ACPI/PNP
registry, are still neglecting the process.

> According to the fact that there are other Linux RTC drivers on the Kernel mainline[6] which support ACPI matching that also do not have ACPI Specification compatible IDs we used that as an example for our first patch attempt.

I answered this in previous mail.

> A PNP ID for SEIKO EPSON is already registered at UEFI database[7].
>
> What I kindly ask your for is an ACPI Specification conforming Product Identifier for the RX6110SA RTC ?
> According to [5] this Product Identifier should be "... always four-character hexadecimal numbers (0-9 and A-F)".
>
> In case you do not know it our can not acquire/create one could you please redirect me to someone from SEIKO EPSON who can help me with that demand ?

So, to be on the constructive page (I thought initially you are from G
company, but anyway) you may do the following:

- (for prototyping only) you may use the PRP0001 approach, described in [8]
- you may issue an ID under your (Siemens) vendor ID
- you may insist G company to issue the ID under their vendor space
(thru coreboot)
- (the best option) to communicate to Seiko Epson to get official ID
from them for this component (and ID mustn't abuse 6.1.5)

Unfortunately I have no contacts there, but I think the best effort is
to contact their support and at the same time ask ASWG [9] how to
proceed. I Cc'ed this to ACPI people in Linux kernel, maybe they can
help.

Of course you have choice to push bad ID forward and use precedence
(like many other companies, even Intel in past, do with firmwares and
Linux kernel is full of badly formed IDs), but since the change is not
existed in read devices I would really like to see proper process to
be followed.

In the Linux kernel I'm in principle trying to prevent bad IDs from
happening as much as I can.

> [1]: (https://mall.industry.siemens.com/mall/en/WW/Catalog/Product/6ES7677-2DB42-0GB0)
> [2]: https://lkml.org/lkml/2020/11/12/561
> [3]: https://review.coreboot.org/c/coreboot/+/47235
> [4]: https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf
> [5]: https://www.uefi.org/PNP_ACPI_Registry
> [6]: https://elixir.bootlin.com/linux/latest/source/drivers/rtc/rtc-ds1307.c#L1142
> [7]: https://www.uefi.org/PNP_ID_List?search=SEIKO+EPSON

[8]: https://elixir.bootlin.com/linux/latest/source/Documentation/firmware-guide/acpi/enumeration.rst
[9]: https://www.uefi.org/workinggroups

> > Before adding new ACPI ID, can you provide an evidence (either from
> > vendor of the component, or a real snapshot of DSDT from device on
> > market) that this is real ID?
> >
> > Before that happens, NAK.
> >
> > P.S. Seems to me that this is kinda cargo cult patch because proposed
> > ID is against ACPI and PNP registry and ACPI specification.
>
> In fact we pushed it in coreboot and Linux at the same time.
>
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Freview.coreboot.org%2Fc%2Fcoreboot%2F%2B%2F47235&amp;data=04%7C01%7Cjohannes-hahn%40siemens.com%7C21c9e1fe99274df7951a08d88a448af5%7C38ae3bcd95794fd4addab42e1495d55a%7C1%7C0%7C637411374276831534%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=7EVdO%2F77LNyvux0y3m9nEf2HZO%2BDm2WkWMfxzaJUoto%3D&amp;reserved=0
>
> That is the evidence. But in case this is wrong we can probably still change coreboot, even though the patches have been merged there already.
>
> Maybe you can go into detail where you see the violations and maybe even suggest fixes that come to mind.

--
With Best Regards,
Andy Shevchenko