On Thu, Sep 20, 2018 at 10:13:57PM +0200, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@xxxxxxxxxx>
>
> For years arm has been using serial.h from asm-generic which sets
> BASE_BAUD value to the (1843200 / 16). This is incorrect as:
> 1) This value obviously isn't correct for all devices
> 2) There are no device specific serial.h with CONFIG_ARCH_MULTIPLATFORM
This goes back a long way. The BASE_BAUD definition is the base baud
for 8250 compatible UARTs _only_, no others.
However, as of 182ead3e418a ("earlycon: Remove hardcoded port->uartclk
initialization in of_setup_earlycon"), port->uartclk is no longer
initialised using BASE_BAUD. As acknowledged in 814453adea7d
("earlycon: Initialize port->uartclk based on clock-frequency property")
the initialisation using BASE_BAUD was bogus, and there is now the
clock-frequency DT property which should be present to set this up.
Now, setting BASE_BAUD to zero as per your patch will break the
8250 serial driver - this relies on BASE_BAUD being set to the
current value, and yes, ARM hardware that uses this will break. So
this is not a solution.
The only solution is that BASE_BAUD must not be abused - it must not
be used by non-8250 hardware, and thankfully there are already
solutions in the kernel (such as clock-frequency) to allow the clock
rate to be specified.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 13.8Mbps down 630kbps up
According to speedtest.net: 13Mbps down 490kbps up
