diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.9/950-0195-amba_pl011-Round-input-clock-up.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.9/950-0195-amba_pl011-Round-input-clock-up.patch | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/target/linux/brcm2708/patches-4.9/950-0195-amba_pl011-Round-input-clock-up.patch b/target/linux/brcm2708/patches-4.9/950-0195-amba_pl011-Round-input-clock-up.patch new file mode 100644 index 0000000..2bd501d --- /dev/null +++ b/target/linux/brcm2708/patches-4.9/950-0195-amba_pl011-Round-input-clock-up.patch @@ -0,0 +1,86 @@ +From 0360d687752df3c5546dd1534904a6e0168b6360 Mon Sep 17 00:00:00 2001 +From: Phil Elwell <phil@raspberrypi.org> +Date: Wed, 1 Mar 2017 16:07:39 +0000 +Subject: [PATCH] amba_pl011: Round input clock up + +The UART clock is initialised to be as close to the requested +frequency as possible without exceeding it. Now that there is a +clock manager that returns the actual frequencies, an expected +48MHz clock is reported as 47999625. If the requested baudrate +== requested clock/16, there is no headroom and the slight +reduction in actual clock rate results in failure. + +Detect cases where it looks like a "round" clock was chosen and +adjust the reported clock to match that "round" value. As the +code comment says: + +/* + * If increasing a clock by less than 0.1% changes it + * from ..999.. to ..000.., round up. + */ + +Signed-off-by: Phil Elwell <phil@raspberrypi.org> +--- + drivers/tty/serial/amba-pl011.c | 23 +++++++++++++++++++++-- + 1 file changed, 21 insertions(+), 2 deletions(-) + +--- a/drivers/tty/serial/amba-pl011.c ++++ b/drivers/tty/serial/amba-pl011.c +@@ -1646,6 +1646,23 @@ static void pl011_put_poll_char(struct u + + #endif /* CONFIG_CONSOLE_POLL */ + ++unsigned long pl011_clk_round(unsigned long clk) ++{ ++ unsigned long scaler; ++ ++ /* ++ * If increasing a clock by less than 0.1% changes it ++ * from ..999.. to ..000.., round up. ++ */ ++ scaler = 1; ++ while (scaler * 100000 < clk) ++ scaler *= 10; ++ if ((clk + scaler - 1)/scaler % 1000 == 0) ++ clk = (clk/scaler + 1) * scaler; ++ ++ return clk; ++} ++ + static int pl011_hwinit(struct uart_port *port) + { + struct uart_amba_port *uap = +@@ -1662,7 +1679,7 @@ static int pl011_hwinit(struct uart_port + if (retval) + return retval; + +- uap->port.uartclk = clk_get_rate(uap->clk); ++ uap->port.uartclk = pl011_clk_round(clk_get_rate(uap->clk)); + + /* Clear pending error and receive interrupts */ + pl011_write(UART011_OEIS | UART011_BEIS | UART011_PEIS | +@@ -2300,7 +2317,7 @@ static int __init pl011_console_setup(st + plat->init(); + } + +- uap->port.uartclk = clk_get_rate(uap->clk); ++ uap->port.uartclk = pl011_clk_round(clk_get_rate(uap->clk)); + + if (uap->vendor->fixed_options) { + baud = uap->fixed_baud; +@@ -2372,6 +2389,7 @@ static struct uart_driver amba_reg = { + .cons = AMBA_CONSOLE, + }; + ++#if 0 + static int pl011_probe_dt_alias(int index, struct device *dev) + { + struct device_node *np; +@@ -2403,6 +2421,7 @@ static int pl011_probe_dt_alias(int inde + + return ret; + } ++#endif + + /* unregisters the driver also if no more ports are left */ + static void pl011_unregister_port(struct uart_amba_port *uap) |