| Message ID | fd06c40a-4f63-3b93-8471-477506f4ef38@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RFC] tty: serial: meson: add new compatible for gxl uart | expand |
Hi, On 25/04/2022 22:39, Heiner Kallweit wrote: > My SC2 test system (ah212-based HK1 RBOX X4) uses an uboot console > speed of 921600 bps. Being able to use the same speed in Linux > requires using a 12MHz clock source. Ideally we'd set the new > compatible to the first chip version supporting the > AML_UART_BAUD_XTAL_DIV2 bit. Actually G12A is the first chip having AML_UART_BAUD_XTAL_DIV2, but SC2 is the first one requiring it to achieve 921600 bps correctly. > Not having access to chip documentation > I'd appreciate a hint on when this bit was introduced. > If fine with you in general the final series would include a > separate patch for the new compatible. This has been already handled in: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-next&id=368ab68b18de104719f386a5cfe3595673cc96de https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-next&id=00a7fa836dbc454faf5b7027ad67519af7c6c15b https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-next&id=9b92cc5ee2d10e6c4d327d1e4ceb77aa8b1081ee > > Note: This patch doesn't consider "tty: serial: meson: > Use DIV_ROUND_CLOSEST to calculate baud rates" yet and therefore > won't apply cleanly on linux-next. > I locally used the same DIV_ROUND_CLOSEST() changes before. > ---------------------------------------------------------------- > Newer SoC versions support using XTAL / 2 (12MHz) as clock source > for the UART. This clock source allows to support 921600 bps as used > by vendor uboot on certain systems like ah212 ref board. > > 12MHz / 13 = 923076 bps > With the currently used 8MHz clock source only 888888bps or > 1000000 bps are possible. > > Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> > --- > drivers/tty/serial/meson_uart.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c > index 2bf1c57e0..0a0a0636f 100644 > --- a/drivers/tty/serial/meson_uart.c > +++ b/drivers/tty/serial/meson_uart.c > @@ -68,6 +68,7 @@ > #define AML_UART_BAUD_MASK 0x7fffff > #define AML_UART_BAUD_USE BIT(23) > #define AML_UART_BAUD_XTAL BIT(24) > +#define AML_UART_BAUD_XTAL_DIV2 BIT(27) > > #define AML_UART_PORT_NUM 12 > #define AML_UART_PORT_OFFSET 6 > @@ -299,10 +300,15 @@ static void meson_uart_change_speed(struct uart_port *port, unsigned long baud) > cpu_relax(); > > if (port->uartclk == 24000000) { > - val = ((port->uartclk / 3) / baud) - 1; > - val |= AML_UART_BAUD_XTAL; > + if (of_device_is_compatible(port->dev->of_node, "amlogic,meson-gxl-uart")) { > + val = DIV_ROUND_CLOSEST(port->uartclk, 2 * baud) - 1; > + val |= AML_UART_BAUD_XTAL | AML_UART_BAUD_XTAL_DIV2; > + } else { > + val = DIV_ROUND_CLOSEST(port->uartclk, 3 * baud) - 1; > + val |= AML_UART_BAUD_XTAL; > + } > } else { > - val = ((port->uartclk * 10 / (baud * 4) + 5) / 10) - 1; > + val = DIV_ROUND_CLOSEST(port->uartclk, 4 * baud) - 1; > } > val |= AML_UART_BAUD_USE; > writel(val, port->membase + AML_UART_REG5); > @@ -782,6 +788,7 @@ static const struct of_device_id meson_uart_dt_match[] = { > { .compatible = "amlogic,meson8-uart" }, > { .compatible = "amlogic,meson8b-uart" }, > { .compatible = "amlogic,meson-gx-uart" }, > + { .compatible = "amlogic,meson-gxl-uart" }, > { /* sentinel */ }, > }; > MODULE_DEVICE_TABLE(of, meson_uart_dt_match);
On 26.04.2022 09:21, Neil Armstrong wrote: > Hi, > > On 25/04/2022 22:39, Heiner Kallweit wrote: >> My SC2 test system (ah212-based HK1 RBOX X4) uses an uboot console >> speed of 921600 bps. Being able to use the same speed in Linux >> requires using a 12MHz clock source. Ideally we'd set the new >> compatible to the first chip version supporting the >> AML_UART_BAUD_XTAL_DIV2 bit. > > Actually G12A is the first chip having AML_UART_BAUD_XTAL_DIV2, but SC2 is > the first one requiring it to achieve 921600 bps correctly. > >> Not having access to chip documentation >> I'd appreciate a hint on when this bit was introduced. >> If fine with you in general the final series would include a >> separate patch for the new compatible. > > This has been already handled in: > https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-next&id=368ab68b18de104719f386a5cfe3595673cc96de > https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-next&id=00a7fa836dbc454faf5b7027ad67519af7c6c15b > https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-next&id=9b92cc5ee2d10e6c4d327d1e4ceb77aa8b1081ee > Good to know, thanks for the hint! >> >> Note: This patch doesn't consider "tty: serial: meson: >> Use DIV_ROUND_CLOSEST to calculate baud rates" yet and therefore >> won't apply cleanly on linux-next. >> I locally used the same DIV_ROUND_CLOSEST() changes before. >> ---------------------------------------------------------------- >> Newer SoC versions support using XTAL / 2 (12MHz) as clock source >> for the UART. This clock source allows to support 921600 bps as used >> by vendor uboot on certain systems like ah212 ref board. >> >> 12MHz / 13 = 923076 bps >> With the currently used 8MHz clock source only 888888bps or >> 1000000 bps are possible. >> >> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> >> --- >> drivers/tty/serial/meson_uart.c | 13 ++++++++++--- >> 1 file changed, 10 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c >> index 2bf1c57e0..0a0a0636f 100644 >> --- a/drivers/tty/serial/meson_uart.c >> +++ b/drivers/tty/serial/meson_uart.c >> @@ -68,6 +68,7 @@ >> #define AML_UART_BAUD_MASK 0x7fffff >> #define AML_UART_BAUD_USE BIT(23) >> #define AML_UART_BAUD_XTAL BIT(24) >> +#define AML_UART_BAUD_XTAL_DIV2 BIT(27) >> #define AML_UART_PORT_NUM 12 >> #define AML_UART_PORT_OFFSET 6 >> @@ -299,10 +300,15 @@ static void meson_uart_change_speed(struct uart_port *port, unsigned long baud) >> cpu_relax(); >> if (port->uartclk == 24000000) { >> - val = ((port->uartclk / 3) / baud) - 1; >> - val |= AML_UART_BAUD_XTAL; >> + if (of_device_is_compatible(port->dev->of_node, "amlogic,meson-gxl-uart")) { >> + val = DIV_ROUND_CLOSEST(port->uartclk, 2 * baud) - 1; >> + val |= AML_UART_BAUD_XTAL | AML_UART_BAUD_XTAL_DIV2; >> + } else { >> + val = DIV_ROUND_CLOSEST(port->uartclk, 3 * baud) - 1; >> + val |= AML_UART_BAUD_XTAL; >> + } >> } else { >> - val = ((port->uartclk * 10 / (baud * 4) + 5) / 10) - 1; >> + val = DIV_ROUND_CLOSEST(port->uartclk, 4 * baud) - 1; >> } >> val |= AML_UART_BAUD_USE; >> writel(val, port->membase + AML_UART_REG5); >> @@ -782,6 +788,7 @@ static const struct of_device_id meson_uart_dt_match[] = { >> { .compatible = "amlogic,meson8-uart" }, >> { .compatible = "amlogic,meson8b-uart" }, >> { .compatible = "amlogic,meson-gx-uart" }, >> + { .compatible = "amlogic,meson-gxl-uart" }, >> { /* sentinel */ }, >> }; >> MODULE_DEVICE_TABLE(of, meson_uart_dt_match); >
diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c index 2bf1c57e0..0a0a0636f 100644 --- a/drivers/tty/serial/meson_uart.c +++ b/drivers/tty/serial/meson_uart.c @@ -68,6 +68,7 @@ #define AML_UART_BAUD_MASK 0x7fffff #define AML_UART_BAUD_USE BIT(23) #define AML_UART_BAUD_XTAL BIT(24) +#define AML_UART_BAUD_XTAL_DIV2 BIT(27) #define AML_UART_PORT_NUM 12 #define AML_UART_PORT_OFFSET 6 @@ -299,10 +300,15 @@ static void meson_uart_change_speed(struct uart_port *port, unsigned long baud) cpu_relax(); if (port->uartclk == 24000000) { - val = ((port->uartclk / 3) / baud) - 1; - val |= AML_UART_BAUD_XTAL; + if (of_device_is_compatible(port->dev->of_node, "amlogic,meson-gxl-uart")) { + val = DIV_ROUND_CLOSEST(port->uartclk, 2 * baud) - 1; + val |= AML_UART_BAUD_XTAL | AML_UART_BAUD_XTAL_DIV2; + } else { + val = DIV_ROUND_CLOSEST(port->uartclk, 3 * baud) - 1; + val |= AML_UART_BAUD_XTAL; + } } else { - val = ((port->uartclk * 10 / (baud * 4) + 5) / 10) - 1; + val = DIV_ROUND_CLOSEST(port->uartclk, 4 * baud) - 1; } val |= AML_UART_BAUD_USE; writel(val, port->membase + AML_UART_REG5); @@ -782,6 +788,7 @@ static const struct of_device_id meson_uart_dt_match[] = { { .compatible = "amlogic,meson8-uart" }, { .compatible = "amlogic,meson8b-uart" }, { .compatible = "amlogic,meson-gx-uart" }, + { .compatible = "amlogic,meson-gxl-uart" }, { /* sentinel */ }, }; MODULE_DEVICE_TABLE(of, meson_uart_dt_match);
My SC2 test system (ah212-based HK1 RBOX X4) uses an uboot console speed of 921600 bps. Being able to use the same speed in Linux requires using a 12MHz clock source. Ideally we'd set the new compatible to the first chip version supporting the AML_UART_BAUD_XTAL_DIV2 bit. Not having access to chip documentation I'd appreciate a hint on when this bit was introduced. If fine with you in general the final series would include a separate patch for the new compatible. Note: This patch doesn't consider "tty: serial: meson: Use DIV_ROUND_CLOSEST to calculate baud rates" yet and therefore won't apply cleanly on linux-next. I locally used the same DIV_ROUND_CLOSEST() changes before. ---------------------------------------------------------------- Newer SoC versions support using XTAL / 2 (12MHz) as clock source for the UART. This clock source allows to support 921600 bps as used by vendor uboot on certain systems like ah212 ref board. 12MHz / 13 = 923076 bps With the currently used 8MHz clock source only 888888bps or 1000000 bps are possible. Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> --- drivers/tty/serial/meson_uart.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)