linux-kernel - Re: [PATCH v2 2/2] serial: 8250

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Message-ID: <ZxZDFiUANo0Jqaai@smile.fi.intel.com>
Date: Mon, 21 Oct 2024 15:03:34 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: Inochi Amaoto <inochiama@...il.com>,
	Chen Wang <unicorn_wang@...look.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Inochi Amaoto <inochiama@...look.com>, Yixun Lan <dlan@...too.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-serial <linux-serial@...r.kernel.org>,
	devicetree@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 2/2] serial: 8250_dw: Add Sophgo SG2044 quirk

On Mon, Oct 21, 2024 at 01:17:55PM +0300, Ilpo Järvinen wrote:
> On Mon, 21 Oct 2024, Inochi Amaoto wrote:
> > On Mon, Oct 21, 2024 at 11:52:38AM +0300, Ilpo Järvinen wrote:
> > > On Mon, 21 Oct 2024, Inochi Amaoto wrote:

> > > > SG2044 relys on an internal divisor when calculating bitrate, which
> > > > means a wrong clock for the most common bitrates. So add a quirk for
> > > > this uart device to skip the set rate call and only relys on the
> > > > internal UART divisor.
> > > > 
> > > > Signed-off-by: Inochi Amaoto <inochiama@...il.com>
> > > 
> > > Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> > > 
> > > I wonder though does this mean the numbers userspace can read from kernel 
> > > are bogus and if something can be done about that?
> > 
> > I am not sure whether the clock rate can be read by the userspace.
> > At least it report the right baud speed by using stty.
> 
> Okay, I meant baud & other settings. Thanks for checking it.

oBut there is clock rate for user space. I think Ilpo has a point.

Documentation/ABI/testing/sysfs-tty:21:What:            /sys/class/tty/ttyS<x>/uartclk

-- 
With Best Regards,
Andy Shevchenko