From: Martin Sperl <kernel@xxxxxxxxxxxxxxxx> The bcm2835 SOC contains an auxiliary uart, which is very close to the ns16550 with some differences. The big difference is that the uart HW is not using an internal divider of 16 but 8, which results in an effictive baud-rate being twice the requested baud-rate. The bcm2835-aux-uart is also special in such that it is enabled/disabled by a gate in the clock, which is managed by the clk-bcm2835-aux clock driver. there are 2 options: * defining the clock-frequency property in the device tree to 500k instead of 250k, but this keeps the HW block disabled making the uart not work. * defining a clock in the device tree, but this results in a baud rate that is twice the requested baud-rate. To address this this patch-set introduce a new property in the device tree to define a clock divider other than 16. This currently just scales the clock by a factor of 16/divider. Note that the use of fixed-factor-clock has also been proposed as a workarround, but this does not really describe the hw in the device tree so another solution was needed that allows a correct representation of the HW in the device tree. Martin Sperl (4): serial: of-serial: allow for a custom clock divider different from 16 dt/bindings: serial: of-serial: add description for clock-divider property serial: bcm2835: add auxiliary uart1 to device tree of bcm2835 ARM: bcm2835: add of-serial and 8250 to bcm2835_defconfig Documentation/devicetree/bindings/serial/8250.txt | 1 + arch/arm/boot/dts/bcm2835.dtsi | 11 +++++++++++ arch/arm/configs/bcm2835_defconfig | 7 +++++++ drivers/tty/serial/of_serial.c | 14 ++++++++++++++ 4 files changed, 33 insertions(+) -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html