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@gmail.com>
---
 drivers/tty/serial/8250/8250_dw.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index ab9e7f204260..6b7c75670f29 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -750,6 +750,11 @@ static const struct dw8250_platform_data dw8250_renesas_rzn1_data = {
 	.quirks = DW_UART_QUIRK_CPR_VALUE | DW_UART_QUIRK_IS_DMA_FC,
 };
 
+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,
@@ -760,6 +765,7 @@ static const struct of_device_id dw8250_of_match[] = {
 	{ .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 },
 	{ /* Sentinel */ }
 };
-- 
2.47.0

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.

...

>  	{ .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.

-- 
With Best Regards,
Andy Shevchenko

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