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Tegra has 5 UARTS which could be used for low-level debug output. Commit
fe26398 "ARM: tegra: uncompress.h: Choose a UART at runtime" implemented
one method for the kernel to automatically determine which of these to
use at run-time, so that the same DEBUG_LL-enabled kernel image could be
used across multiple Tegra boards. The required bootloader-side setup for
that option is implemented in NVIDIA's various downstream U-Boot branches,
but the U-Boot maintainers have refused to accept it upstream.
This change implements an alternative automatic UART selection option
using ODMDATA. This is a 32-bit value programmed into Tegra's boot memory
which provides a few pieces of basic board-specific information, including
a field that indicates the console UART. Setting up this value is part of
the standard Tegra boot architecture, and so requires no Tegra-specific
hacks in the bootloader's UART driver.
Note that in theory, the format of ODMDATA is board-specific. However, in
practice all boards use the same location/size/values for the UART field.
ODMDATA[19:18] (which drive the type of debug console) is more problematic,
since some boards use value 2 for UART and others use 3. This patch just
accepts either value; if this doesn't work well for a given board, I'd
suggest simply not enabling this debug option when building for that board.
Note that the kernel assumes the bootloader has already set up any required
pinmux settings for the UART; there is no way the kernel can do this for
itself prior to knowing which board it's running on. In practice, people
using this feature are highly likely to be using bootloaders that have
indeed configured the pinmux. This assumption existed prior to this patch.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
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This fixes the following compile error:
CC arch/arm/boot/compressed/misc.o
In file included from arch/arm/boot/compressed/misc.c:28:0:
arch/arm/mach-tegra/include/mach/uncompress.h: In function 'arch_decomp_setup':
arch/arm/mach-tegra/include/mach/uncompress.h:125:2: error: implicit declaration of function 'BUILD_BUG_ON_ZERO' [-Werror=implicit-function-declaration]
cc1: some warnings being treated as errors
This is due to use of the ARRAY_SIZE() macro. Typically, this would be
solved by including <linux/bug.h>, but the compressor code isn't part of
the kernel, and so should not include kernel headers. Instead, define
the few macros the code uses directly, and in a way that doesn't depend
on <linux/bug.h>.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>
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uncompress.h now saves the selected UART's physical address in Tegra's
IRAM, along with a cookie to indicate validity.
The first time it's run, macro addruart in debug-macro.S looks for this
cookie, and if it's present, uses the UART address stored there. If not,
the static value TEGRA_DEBUG_UART_BASE is used, as was previous behaviour.
The static behaviour will thus be used when not booting using a zImage.
This work was inspired by work by Doug Anderson <dianders@chromium.org>;
see http://lkml.org/lkml/2011/9/26/284. However, this patch relies on
the data passing describe above, rather than duplicating the UART
selection logic in debug-macro.S; the latest selection logic is more
complex due to the need to check reset/clock bits too.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Doug Anderson <dianders@chromium.org>
Acked-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Olof Johansson <olof@lixom.net>
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With this change we automatically detect which UART to use for
for printing during decompression. The detection involves coordination
with the bootloader: it's expected that the bootloader will leave a
'D' (for [D]ebug) in the UART scratchpad register for whichever UART we
should use for debugging.
If we don't find any such UART, we fall back to the UART that was
specified during config time: CONFIG_TEGRA_DEBUG_UART_XXX.
As a side effect of this change, uncompress debug messages will work
if you've specified CONFIG_TEGRA_DEBUG_UART_NONE, provided the
bootloader obeys the protocol.
This change is in line with what is documented in
Documentation/arm/Booting.
Other approaches considered:
* Hardcode based on machine ID (as many other ARM boards do).
OK, but nice to not have yet another place to add per-board
code. Better to have bootloader parse device tree and pass us
this info.
* Check for TXE bit (like SA1110). Nice (and doesn't require
a bootloader change), but a little less explicit. Also: if
bootloader (for some reason) uses another UART, it needs to
remember to turn it off before jumping to the kernel or we may
print to it. NOTE: adapting this patch to check TXE too would
be easy if desired.
Signed-off-by: Doug Anderson <dianders@chromium.org>
[swarren: Added clock/reset condition checks]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Doug Anderson <dianders@chromium.org>
Acked-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Olof Johansson <olof@lixom.net>
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This will allow a future change to auto-detect which UART to use.
Signed-off-by: Doug Anderson <dianders@chromium.org>
[swarren: Extracted from a larger patch by Doug]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Doug Anderson <dianders@chromium.org>
Acked-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Olof Johansson <olof@lixom.net>
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This removes the need for the variable "shift" in all functions in
uncompress.h.
Signed-off-by: Doug Anderson <dianders@chromium.org>
[swarren: Extracted from a larger patch by Doug]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Doug Anderson <dianders@chromium.org>
Acked-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Olof Johansson <olof@lixom.net>
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On Tegra20, the UART clock runs at 216MHz, whereas on Tegra30 it runs at
408MHz. Modify arch_decomp_setup() to detect Tegra20-vs-Tegra30 at run-
time, and program the correct divisor.
This makes uncompressor messages work correctly on Tegra30. This also
fixes early printk, assuming zImage is used and this setup code runs.
v2: Use CHIPID register to differentiate between chips, rather than a
GIC register. This should be more future-proof. Volatile is required
to prevent the compiler transforming the 32-bit apb_misc register read
into an 8-bit read of address 1 higher, since the HW only supports 32-
bit accesses, and will hang on an 8-bit access.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>
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Signed-off-by: Colin Cross <ccross@android.com>
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v2: Fixes from Mike Rapoport
- remove unused header files (mach/dma.h and mach/nand.h)
- remove tegra 1 references from Makefile.boot
v2: fixes from Russell King
- remove mach/io.h include from mach/iomap.h
- fix whitespace in Kconfig
v2: from Colin Cross
- fix invalid immediate in debug-macro.S
v3:
- allow selection of multiple boards
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Erik Gilling <konkers@android.com>
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