[PATCH] ARM: allow DEBUG_UNCOMPRESS for omap2plus

[PATCH] ARM: allow DEBUG_UNCOMPRESS for omap2plus

[Stephen Warren]

From: Stephen Warren <swarren@nvidia.com>

DEBUG_UNCOMPRESS was previously disallowed for omap2plus due to
omap2plus.S's use of .data, which is not allowed in the decompressor.
Solve this by placing that data into .text when building the file into
the decompressor. This relies on .text actually being writable in the
decompressor, which it is in practice.

Cc: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
Note that I have build-tested this with omap2plus_defconfig, but not
run-time tested it in any way.
---
 arch/arm/Kconfig.debug             | 2 +-
 arch/arm/include/debug/omap2plus.S | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index d8ff7f7..8eb04b1 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -1046,7 +1046,7 @@ config DEBUG_UART_8250_FLOW_CONTROL
 config DEBUG_UNCOMPRESS
 	bool
 	depends on ARCH_MULTIPLATFORM
-	default y if DEBUG_LL && !DEBUG_OMAP2PLUS_UART
+	default y if DEBUG_LL
 	help
 	  This option influences the normal decompressor output for
 	  multiplatform kernels.  Normally, multiplatform kernels disable
diff --git a/arch/arm/include/debug/omap2plus.S b/arch/arm/include/debug/omap2plus.S
index 6d867ae..364ae35 100644
--- a/arch/arm/include/debug/omap2plus.S
+++ b/arch/arm/include/debug/omap2plus.S
@@ -58,11 +58,15 @@
 
 #define UART_OFFSET(addr)	((addr) & 0x00ffffff)
 
+#if !defined(ZIMAGE)
 		.pushsection .data
+#endif
 omap_uart_phys:	.word	0
 omap_uart_virt:	.word	0
 omap_uart_lsr:	.word	0
+#if !defined(ZIMAGE)
 		.popsection
+#endif
 
 		.macro	addruart, rp, rv, tmp
 
-- 
1.8.1.5

Re: [PATCH] ARM: allow DEBUG_UNCOMPRESS for omap2plus

[Russell King - ARM Linux]

On Tue, Jul 30, 2013 at 04:49:18PM -0600, Stephen Warren wrote:
> From: Stephen Warren <swarren@nvidia.com>
> 
> DEBUG_UNCOMPRESS was previously disallowed for omap2plus due to
> omap2plus.S's use of .data, which is not allowed in the decompressor.
> Solve this by placing that data into .text when building the file into
> the decompressor. This relies on .text actually being writable in the
> decompressor, which it is in practice.

Unless you decide to use ZBOOT and flash the zImage.

Re: [PATCH] ARM: allow DEBUG_UNCOMPRESS for omap2plus

[Stephen Warren]

On 07/30/2013 04:52 PM, Russell King - ARM Linux wrote:
> On Tue, Jul 30, 2013 at 04:49:18PM -0600, Stephen Warren wrote:
>> From: Stephen Warren <swarren@nvidia.com>
>>
>> DEBUG_UNCOMPRESS was previously disallowed for omap2plus due to
>> omap2plus.S's use of .data, which is not allowed in the decompressor.
>> Solve this by placing that data into .text when building the file into
>> the decompressor. This relies on .text actually being writable in the
>> decompressor, which it is in practice.
> 
> Unless you decide to use ZBOOT and flash the zImage.

I knew there had to be a catch:-)

I have no idea if ZBOOT is a use-case that's relevant to OMAP?

On Tegra at least (the same issue applies to the other patch I just
sent), that use-case is almost impossible; even if the boot ROM directly
booted a kernel, the boot ROM is hard-coded to copy whatever it's
booting to SDRAM first, although I suppose if that was a boot-loader it
could just jump back to a ROM location. That said, NOR flash is
extremely rare on Tegra. So, I don't know if we care about this issue.

Is it reasonable to just say "If you use ZBOOT, don't enable
DEBUG_UNCOMPRESS"? Perhaps these patches should not completely remove
the !DEBUG_TEGRA_UART from config DEBUG_UNCOMPRESS, but instead say:

default y if DEBUG_LL && (!DEBUG_TEGRA_UART || !ZBOOT)?

Re: [PATCH] ARM: allow DEBUG_UNCOMPRESS for omap2plus

[Tony Lindgren]

* Stephen Warren <swarren@wwwdotorg.org> [130730 16:08]:
> On 07/30/2013 04:52 PM, Russell King - ARM Linux wrote:
> > On Tue, Jul 30, 2013 at 04:49:18PM -0600, Stephen Warren wrote:
> >> From: Stephen Warren <swarren@nvidia.com>
> >>
> >> DEBUG_UNCOMPRESS was previously disallowed for omap2plus due to
> >> omap2plus.S's use of .data, which is not allowed in the decompressor.
> >> Solve this by placing that data into .text when building the file into
> >> the decompressor. This relies on .text actually being writable in the
> >> decompressor, which it is in practice.
> > 
> > Unless you decide to use ZBOOT and flash the zImage.
> 
> I knew there had to be a catch:-)
> 
> I have no idea if ZBOOT is a use-case that's relevant to OMAP?
> 
> On Tegra at least (the same issue applies to the other patch I just
> sent), that use-case is almost impossible; even if the boot ROM directly
> booted a kernel, the boot ROM is hard-coded to copy whatever it's
> booting to SDRAM first, although I suppose if that was a boot-loader it
> could just jump back to a ROM location. That said, NOR flash is
> extremely rare on Tegra. So, I don't know if we care about this issue.
> 
> Is it reasonable to just say "If you use ZBOOT, don't enable
> DEBUG_UNCOMPRESS"? Perhaps these patches should not completely remove
> the !DEBUG_TEGRA_UART from config DEBUG_UNCOMPRESS, but instead say:
> 
> default y if DEBUG_LL && (!DEBUG_TEGRA_UART || !ZBOOT)?

I think we're best off removing the remaining uncompress code
configured port detection features as the port properties are now
defined in kconfig anyways. That simplifies the code quite a bit.

Regards,

Tony

Re: [PATCH] ARM: allow DEBUG_UNCOMPRESS for omap2plus

[Stephen Warren]

On 07/31/2013 12:46 AM, Tony Lindgren wrote:
> * Stephen Warren <swarren@wwwdotorg.org> [130730 16:08]:
>> On 07/30/2013 04:52 PM, Russell King - ARM Linux wrote:
>>> On Tue, Jul 30, 2013 at 04:49:18PM -0600, Stephen Warren wrote:
>>>> From: Stephen Warren <swarren@nvidia.com>
>>>>
>>>> DEBUG_UNCOMPRESS was previously disallowed for omap2plus due to
>>>> omap2plus.S's use of .data, which is not allowed in the decompressor.
>>>> Solve this by placing that data into .text when building the file into
>>>> the decompressor. This relies on .text actually being writable in the
>>>> decompressor, which it is in practice.
>>>
>>> Unless you decide to use ZBOOT and flash the zImage.
>>
>> I knew there had to be a catch:-)
>>
>> I have no idea if ZBOOT is a use-case that's relevant to OMAP?
>>
>> On Tegra at least (the same issue applies to the other patch I just
>> sent), that use-case is almost impossible; even if the boot ROM directly
>> booted a kernel, the boot ROM is hard-coded to copy whatever it's
>> booting to SDRAM first, although I suppose if that was a boot-loader it
>> could just jump back to a ROM location. That said, NOR flash is
>> extremely rare on Tegra. So, I don't know if we care about this issue.
>>
>> Is it reasonable to just say "If you use ZBOOT, don't enable
>> DEBUG_UNCOMPRESS"? Perhaps these patches should not completely remove
>> the !DEBUG_TEGRA_UART from config DEBUG_UNCOMPRESS, but instead say:
>>
>> default y if DEBUG_LL && (!DEBUG_TEGRA_UART || !ZBOOT)?
> 
> I think we're best off removing the remaining uncompress code
> configured port detection features as the port properties are now
> defined in kconfig anyways. That simplifies the code quite a bit.

If you want to do that with OMAP, I'm happy to drop this patch.

For Tegra, automatic determination of the DEBUG_LL UART is rather
useful, so I'm not going to give that up:-)

Re: [PATCH] ARM: allow DEBUG_UNCOMPRESS for omap2plus

[Tony Lindgren]

* Stephen Warren <swarren@wwwdotorg.org> [130731 10:04]:
> On 07/31/2013 12:46 AM, Tony Lindgren wrote:
> > 
> > I think we're best off removing the remaining uncompress code
> > configured port detection features as the port properties are now
> > defined in kconfig anyways. That simplifies the code quite a bit.
> 
> If you want to do that with OMAP, I'm happy to drop this patch.

Yes on my list of things to do..
 
> For Tegra, automatic determination of the DEBUG_LL UART is rather
> useful, so I'm not going to give that up:-)

For omaps there's just too many options to try to detect anything.

It seems the best strategy seems to be to just init things later on
so DEBUG_LL is only needed when booting breaks really early on
during the boot process.

Regards,

Tony

Re: [PATCH] ARM: allow DEBUG_UNCOMPRESS for omap2plus

[Russell King - ARM Linux]

On Fri, Aug 02, 2013 at 12:29:25AM -0700, Tony Lindgren wrote:
> It seems the best strategy seems to be to just init things later on
> so DEBUG_LL is only needed when booting breaks really early on
> during the boot process.

... which is exactly the whole point and use case of DEBUG_LL. :)