сб, 22 окт. 2022 г. в 23:07, Paul Cercueil <paul@xxxxxxxxxxxxxxx>: > > Hi Siarhei, > > Le sam. 22 oct. 2022 à 19:50:47 +0300, Siarhei Volkau > <lis8215@xxxxxxxxx> a écrit : > > JZ4750/55/60 (but not JZ4760b) have an extra divisor in between extclk > > and peripheral clock, called CPCCR.ECS, the driver can't figure out > > the > > real state of the divisor without dirty hack - peek CGU CPCCR > > register. > > However, we can rely on a vendor's bootloader (u-boot 1.1.6) behavior: > > if (extclk > 16MHz) > > the divisor is enabled, so the UART driving clock is extclk/2. > > > > This behavior relies on hardware differences: most boards (if not all) > > with those SoCs have 12 or 24 MHz oscillators but many peripherals > > want > > 12Mhz to operate properly (AIC and USB-PHY at least). > > > > The patch doesn't affect JZ4760's behavior as it is subject for > > another > > patchset with re-classification of all supported ingenic UARTs. > > > > Link: > > https://github.com/carlos-wong/uboot_jz4755/blob/master/cpu/mips/jz_serial.c#L158 > > Signed-off-by: Siarhei Volkau <lis8215@xxxxxxxxx> > > --- > > drivers/tty/serial/8250/8250_ingenic.c | 48 > > ++++++++++++++++++++++---- > > 1 file changed, 42 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/tty/serial/8250/8250_ingenic.c > > b/drivers/tty/serial/8250/8250_ingenic.c > > index 2b2f5d8d2..744705467 100644 > > --- a/drivers/tty/serial/8250/8250_ingenic.c > > +++ b/drivers/tty/serial/8250/8250_ingenic.c > > @@ -87,24 +87,19 @@ static void __init > > ingenic_early_console_setup_clock(struct earlycon_device *dev > > dev->port.uartclk = be32_to_cpup(prop); > > } > > > > -static int __init ingenic_early_console_setup(struct earlycon_device > > *dev, > > +static int __init ingenic_earlycon_setup_tail(struct earlycon_device > > *dev, > > const char *opt) > > { > > struct uart_port *port = &dev->port; > > unsigned int divisor; > > int baud = 115200; > > > > - if (!dev->port.membase) > > - return -ENODEV; > > - > > if (opt) { > > unsigned int parity, bits, flow; /* unused for now */ > > > > uart_parse_options(opt, &baud, &parity, &bits, &flow); > > } > > > > - ingenic_early_console_setup_clock(dev); > > - > > if (dev->baud) > > baud = dev->baud; > > divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * baud); > > @@ -129,9 +124,49 @@ static int __init > > ingenic_early_console_setup(struct earlycon_device *dev, > > return 0; > > } > > > > +static int __init ingenic_early_console_setup(struct earlycon_device > > *dev, > > + const char *opt) > > +{ > > + if (!dev->port.membase) > > + return -ENODEV; > > + > > + ingenic_early_console_setup_clock(dev); > > + > > + return ingenic_earlycon_setup_tail(dev, opt); > > +} > > + > > +static int __init jz4750_early_console_setup(struct earlycon_device > > *dev, > > + const char *opt) > > +{ > > + if (!dev->port.membase) > > + return -ENODEV; > > + > > + /* > > + * JZ4750/55/60 (not JZ4760b) have an extra divisor > > + * between extclk and peripheral clock, the > > + * driver can't figure out the real state of the > > + * divisor without dirty hacks (peek CGU register). > > + * However, we can rely on a vendor's behavior: > > + * if (extclk > 16MHz) > > + * the divisor is enabled. > > + * This behavior relies on hardware differences: > > + * most boards with those SoCs have 12 or 24 MHz > > + * oscillators but many peripherals want 12Mhz > > + * to operate properly (AIC and USB-phy at least). > > + */ > > + ingenic_early_console_setup_clock(dev); > > + if (dev->port.uartclk > 16000000) > > + dev->port.uartclk /= 2; > > I don't understand, didn't we came up to the conclusion in your V1 that > it was better to force-enable the EXT/2 divider in the ingenic init > code? > > -Paul > That was better at that moment. I dived deeper in the situation and found a more simple and universal solution, as I think. Your proposal doesn't cover following situations: - JZ475x with 12MHz crystal - JZ4760 with 24MHz crystal which are legal and might appear in some hardware. > > + > > + return ingenic_earlycon_setup_tail(dev, opt); > > +} > > + > > OF_EARLYCON_DECLARE(jz4740_uart, "ingenic,jz4740-uart", > > ingenic_early_console_setup); > > > > +OF_EARLYCON_DECLARE(jz4750_uart, "ingenic,jz4750-uart", > > + jz4750_early_console_setup); > > + > > OF_EARLYCON_DECLARE(jz4770_uart, "ingenic,jz4770-uart", > > ingenic_early_console_setup); > > > > @@ -328,6 +363,7 @@ static const struct ingenic_uart_config > > x1000_uart_config = { > > > > static const struct of_device_id of_match[] = { > > { .compatible = "ingenic,jz4740-uart", .data = &jz4740_uart_config > > }, > > + { .compatible = "ingenic,jz4750-uart", .data = &jz4760_uart_config > > }, > > { .compatible = "ingenic,jz4760-uart", .data = &jz4760_uart_config > > }, > > { .compatible = "ingenic,jz4770-uart", .data = &jz4760_uart_config > > }, > > { .compatible = "ingenic,jz4775-uart", .data = &jz4760_uart_config > > }, > > -- > > 2.36.1 > > > >
