| Message ID | 20241021072606.585878-3-inochiama@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | serial: 8250_dw: Introduce SG2044 uart support. | expand |
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@gmail.com> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@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?
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@gmail.com> > > Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@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); > >
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@gmail.com> > > > > Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@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. Okay, I meant baud & other settings. Thanks for checking it.
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@gmail.com> > > > > > > Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@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. > > 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
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);
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 | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)