[PATCH v2 2/2] serial: 8250_dw: Add Sophgo SG2044 quirk

[Inochi Amaoto]

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 at gmail.com>
> 
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen at linux.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.

Regards,
Inochi

> 
> > ---
> >  drivers/tty/serial/8250/8250_dw.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
> > index ab9e7f204260..51894c93c8a3 100644
> > --- a/drivers/tty/serial/8250/8250_dw.c
> > +++ b/drivers/tty/serial/8250/8250_dw.c
> > @@ -750,7 +750,7 @@ 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_starfive_jh7100_data = {
> > +static const struct dw8250_platform_data dw8250_skip_set_rate_data = {
> >  	.usr_reg = DW_UART_USR,
> >  	.quirks = DW_UART_QUIRK_SKIP_SET_RATE,
> >  };
> > @@ -760,7 +760,8 @@ 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 = "starfive,jh7100-uart", .data = &dw8250_starfive_jh7100_data },
> > +	{ .compatible = "sophgo,sg2044-uart", .data = &dw8250_skip_set_rate_data },
> > +	{ .compatible = "starfive,jh7100-uart", .data = &dw8250_skip_set_rate_data },
> >  	{ /* Sentinel */ }
> >  };
> >  MODULE_DEVICE_TABLE(of, dw8250_of_match);
> >