[PATCH RFC 6/6] arm64: wait for transmit completion before next character transmission
geoff at infradead.org
Fri Apr 17 10:22:23 PDT 2015
On Thu, 2015-04-16 at 22:17 +0530, Pratyush Anand wrote:
> Previous transmission must be completed before next character to be
> transmitted, otherwise TX buffer may saturate and we will not see all
> the characters on screen.
> @@ -34,6 +38,8 @@ static const char arm64_opts_usage __attribute__ ((unused)) =
> " --lite Fast reboot, no memory integrity checks.\n"
> " --page-offset Kernel page-offset for binary image load.\n"
> " --port=ADDRESS Purgatory output to port ADDRESS.\n"
> +" --port-lsr=ADDRESS Purgatory output port line status ADDRESS.\n"
> +" --port-lsr-val=VALUE Purgatory output port Line status expected SET value when TX empty.\n"
> " --ramdisk=FILE Use FILE as the kernel initial ramdisk.\n"
> " --reuse-cmdline Use command line arg of primary kernel.\n";
We just need to put some chars to the screen, so I want to avoid a lot
Usually the status register is at a fixed offset from the TX port. Is
that not the case for the ARM uarts?
Can't we just poll port-lsr until empty then start writing again? That
will at least eliminate port-lsr-val.
More information about the kexec