Re: [PATCH v5 17/17] serial: 8250: Add 8250_acpi driver

Sunil V L
2024-05-02T11:21:14Z

On Thu, May 02, 2024 at 01:09:57PM +0300, Andy Shevchenko wrote:
> On Thu, May 02, 2024 at 03:20:08PM +0530, Sunil V L wrote:
> > On Thu, May 02, 2024 at 12:17:59PM +0300, Andy Shevchenko wrote:
> > > On Wed, May 01, 2024 at 05:47:42PM +0530, Sunil V L wrote:
>
> ...
>
> > > > + * This driver is for generic 16550 compatible UART enumerated via ACPI
> > > > + * platform bus instead of PNP bus like PNP0501. This is not a full
> > >
> > > This has to be told in the commit message. Anyway, we don't need a duplication
> > > code, please use 8250_pnp.
> >
> > Thank you for the review!. Major issue with PNP0501 is, it gets enumerated
> > in a different way which causes issue to get _DEP to work.
> > pnpacpi_init() creates PNP data structures which gets skipped if the
> > UART puts _DEP on the GSI provider (interrupt controller). In that case,
> > we need to somehow reinitialize such PNP devices after interrupt
> > controller gets probed.
>
> Then fix that code, we don't want a hack driver on top of the existing one for
> the same.
>
> What I might think out of head is that used IRQ core for your case should
> return a deferred probe error code when it's not ready, then 8250_pnp will
> get reprobed.
>
Deferred probe was ruled out in prior discussion. Also, deferred probe
will not work with _DEP approach. The reason is, PNP devices itself are
not getting created from the ACPI name space when they have _DEP. Hence,
serial_pnp_probe() will not be called at all.

> > I tried a solution [1] but it required several
> > functions to be moved out of __init.
>
> > This driver is not a duplicate of 8250_pnp. It just relies on UART
> > enumerated as platform device instead of using PNP interfaces.
> > Isn't it better and simple to have an option to enumerate as platform
> > device instead of PNP?
>
> Ah, then extract platform driver first from 8250_core.c.
>
Let me know if I understand your suggestion correctly. Do you mean call
something like serial8250_acpi_init() from serial8250_init() and
register the driver directly in serial8250_acpi_init()?

Thanks,
Sunil