[PATCH 0/4] ARM: tegra: Automatic UART selection for earlyprintk

[Doug Anderson]

For the series,
Tested-by: Doug Anderson <dianders at chromium.org>
Thank you for picking this up.
A few overall comments on the patch set:1. This patch has the side
effect of requiring the use of zImage to    get the proper behavior.
If we ever try to move decompression   of the kernel to the bootloader
(as has been talked about, since   u-boot supports it) we'll lose
earlyprintk behavior.  ...of course,    this does match how some other
ARM boards do things.  I'm OK with   this.2. I'm slightly concerned
about cramming stuff into IRAM, since   I don't have a good concept of
what IRAM adresses are used when.   When I grep for IRAM users in our
kernel, I see    TEGRA_AVP_RESUME_ADDR is using the base of IRAM.
We're not going   to be hosing suspend/resume or anything else with
this CL, are we?   In the very least, I'd perfer to see a #define for
the '0x100' and    the '0x55415254' so that we can correlate the
constants in    uncompress.h and debug-macro.S
Tested:Tested the series on a Tegra2-based board (Kaen)
withCONFIG_TEGRA_DEBUG_UART_NONE defined on the current ToT
chromium-os tree with the following pre-changes:1. Reverted hack from
our tree: 63b76a4638f3934e69c8724881060f121845184c2. Added "arm/tegra:
Support Tegra30 in decompressor UART setup" as   described in the
patch header.3. Adjusted patch 4 to apply cleanly to our older
"common.c"4. Added missing #include <linux/kernel.h> to uncompress.h,
as    indicated by swarren on tegra IRC.
Also tried stopping in the bootloader and clearing the 'D' with:  mw.b
0x7000605c 0...and validated that I missed the earlyprintks (as
expected) butstill booted.
---
On Tue, Jan 3, 2012 at 2:25 PM, Stephen Warren <swarren at nvidia.com> wrote:
> This series allows a Tegra zImage to automatically select the UART to use
> for the zImage decompressor and early printk, based on information from
> the bootloader. The code scans each UART, looking for one that is clocked,
> is out of reset, and that the bootloader has written 'D' (for 'D'ebug) to
> the scratch register.
>
> At present, the ChromiumOS branch of U-Boot sets up UARTs in this way. If
> this patch is accepted into the kernel, I'll upstream the U-Boot change to
> mainline U-Boot.
>
> This is important, since different boards use different UARTs, and it's
> nice not to have to configure the kernel differently when switching
> boards.
>
> This patch series depends on patch "[PATCH V2] arm/tegra: Support Tegra30
> in decompressor UART setup" for context.
>
> Doug Anderson (2):
>  ARM: tegra: Introduce define DEBUG_UART_SHIFT
>  ARM: tegra: uncompress.h: Store UART address in a variable
>
> Stephen Warren (2):
>  ARM: tegra: uncompress.h: Choose a UART at runtime
>  ARM: tegra: Pass uncompress.h UART selection to DEBUG_LL
>
>  arch/arm/mach-tegra/common.c                   |   17 ++++
>  arch/arm/mach-tegra/include/mach/debug-macro.S |   87 +++++++++++++++++---
>  arch/arm/mach-tegra/include/mach/uncompress.h  |  108 +++++++++++++++++++++---
>  3 files changed, 190 insertions(+), 22 deletions(-)
>