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

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Message-ID: <lsv65gsdza77bfhoewuyqznts56hnz2b7cvqxngmy6gktfys35@g7bg5ruug3yc>
Date: Fri, 11 Oct 2024 10:05:40 +0800
From: Inochi Amaoto <inochiama@...il.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Inochi Amaoto <inochiama@...il.com>
Cc: 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>, 
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, Chen Wang <unicorn_wang@...look.com>, 
	Inochi Amaoto <inochiama@...look.com>, Yixun Lan <dlan@...too.org>, linux-kernel@...r.kernel.org, 
	linux-serial@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 2/2] serial: 8250_dw: Add Sophgo SG2044 quirk

On Thu, Oct 10, 2024 at 06:00:34PM +0300, Andy Shevchenko wrote:
> On Thu, Oct 10, 2024 at 07:39:06AM +0800, 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.
> 
> ...
> 
> > +static const struct dw8250_platform_data dw8250_sophgo_sg2044_data = {
> > +	.usr_reg = DW_UART_USR,
> > +	.quirks = DW_UART_QUIRK_SKIP_SET_RATE,
> > +};
> > +
> >  static const struct dw8250_platform_data dw8250_starfive_jh7100_data = {
> >  	.usr_reg = DW_UART_USR,
> >  	.quirks = DW_UART_QUIRK_SKIP_SET_RATE,
> 
> For the bare minimum this should be deduplicated as to have one record for now.
> 
> static const struct dw8250_platform_data dw8250_skip_set_rate_data = {
> 	.usr_reg = DW_UART_USR,
> 	.quirks = DW_UART_QUIRK_SKIP_SET_RATE,
> };
> 
> If we need different quirks in the future, they can be split again.
> Or, if you certain that new quirks will come, mention this in
> the commit message.
> 

Yes, renaming this quirk as a common one is better. I will prefer if
this patch is necessary. Duplication is not a good idea.

> ...
> 
> >  	{ .compatible = "cavium,octeon-3860-uart", .data = &dw8250_octeon_3860_data },
> >  	{ .compatible = "marvell,armada-38x-uart", .data = &dw8250_armada_38x_data },
> >  	{ .compatible = "renesas,rzn1-uart", .data = &dw8250_renesas_rzn1_data },
> > +	{ .compatible = "sophgo,sg2044-uart", .data = &dw8250_sophgo_sg2044_data },
> >  	{ .compatible = "starfive,jh7100-uart", .data = &dw8250_starfive_jh7100_data },
> 
> I think my proposal for having a common compatible for those two is a no-go
> as compatible strings are for the (unique) hardware and shouldn't be abstracted
> based on some Linux or other OS shortcuts / quirks.
> 

Yes, a common compatible is not a good idea. But it is OK to share a common quirk,
which means they have the same problem.

Regards,
Inochi