Hi Siarhei,
Le sam. 22 oct. 2022 à 18:12:24 +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 | 50
++++++++++++++++++++++----
1 file changed, 43 insertions(+), 7 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_ingenic.c
b/drivers/tty/serial/8250/8250_ingenic.c
index 2b2f5d8d2..3ffa6b722 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,
- const char *opt)
+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;
You can keep this here - no need to move it (and it'd avoid duplicating
code).
-
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);
+
+ 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 would assume you could just do:
dev->port.uartclk = 12000000;
Since you'd always get a 12 MHz clock (either with a 12 MHz oscillator
or a 24 MHz oscillator with a /2 divider).
With that said - I am fine with that code, it would allow to fine-tune
the oscillator value (although I hightly doubt anybody is going to do
that).
The 16 MHz value sounds very arbitrary, but I'll give it a pass.
Cheers,
-Paul
+
+ 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
