linux-kernel - Re: [PATCH v5 17/17] serial: 8250: Add 8250

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Message-ID: <ZjNh0Llcx+0VHevy@sunil-laptop>
Date: Thu, 2 May 2024 15:20:08 +0530
From: Sunil V L <sunilvl@...tanamicro.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, linux-acpi@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-serial@...r.kernel.org,
	acpica-devel@...ts.linux.dev,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Anup Patel <anup@...infault.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Samuel Holland <samuel.holland@...ive.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Robert Moore <robert.moore@...el.com>,
	Conor Dooley <conor.dooley@...rochip.com>,
	Andrew Jones <ajones@...tanamicro.com>,
	Marc Zyngier <maz@...nel.org>,
	Atish Kumar Patra <atishp@...osinc.com>,
	Andrei Warkentin <andrei.warkentin@...el.com>,
	Haibo1 Xu <haibo1.xu@...el.com>,
	Björn Töpel <bjorn@...nel.org>
Subject: Re: [PATCH v5 17/17] serial: 8250: Add 8250_acpi driver

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:
> > RISC-V has non-PNP generic 16550A compatible UART which needs to be
> > enumerated as ACPI platform device. Add driver support for such devices
> > similar to 8250_of.
> 
> ...
> 
> > + * 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.
> 
Hi Andy,

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. 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? 

[1] - https://patchwork.kernel.org/project/linux-pci/patch/20240415170113.662318-14-sunilvl@ventanamicro.com/

Thanks,
Sunil
> ...
> 
> > +	{ "RSCV0003", 0 },
> 
> Does it have _CID to be PNP0501?
> If not, add this ID to the 8250_pnp.
> 
> ...
> 
> P.S.
> The code you submitted has a lot of small style issues, I can comment on them
> if you want, but as I said this code is not needed at all.
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
>