Alexander Shishkin had written, on 01/12/2010 03:46 PM, the following:
On Tue, Jan 12, 2010 at 01:04:04 -0800, Tony Lindgren wrote:
* Nishanth Menon <nm@xxxxxx> [100112 09:31]:
Alexander Shishkin had written, on 01/12/2010 11:30 AM, the following:
On Tue, Jan 12, 2010 at 11:13:13 -0600, Nishanth Menon wrote:
Alexander Shishkin had written, on 01/12/2010 11:04 AM, the following:
diff --git a/arch/arm/mach-omap2/sleep34xx.S b/arch/arm/mach-omap2/sleep34xx.S
index 69521be..0a5ec86 100644
--- a/arch/arm/mach-omap2/sleep34xx.S
+++ b/arch/arm/mach-omap2/sleep34xx.S
[...]
/* Store current cpsr*/
mrs r2, cpsr
stmia r8!, {r2}
@@ -520,6 +616,7 @@ clean_caches:
cmp r9, #1 /* Check whether L2 inval is required or not*/
bne skip_l2_inval
clean_l2:
+#if 0
my aversion to #if 0 kicks in here :(.. do we have an alternative
like using the CONFIG_ENABLE_OFF_MODE_JTAG_ETM_DEBUG or something
else?
Fair enough. I could replace it with "#if !defined(...)" as the first
thing that comes to mind. This way it will only take disabling the
config option to catch any possible regressions in between. Does this
sound reasonable?
sounds ok to me.. unless folks have ideas coz of clean_l2 label..
more comments might be useful before a rev2 of the patch..
The best solution would be to be able to toggle this via sysfs or
debugfs by swapping the sram code for idle loop when JTAG support
is needed.
Well, if you say, compile the ETM driver in, this will be needed most of
the time.
I can think of reasons for an against a sysfs entry (as part of
discussion -warning lot of self contradictions below- but I think might
save a bit of back and froth ;)):
for sysfs entry:
a) save and restore will have additional latency when you save a chunk
such as EMU domain regs - this will not be needed in production phones,
disabling it might pop up surprises
counter: having a disabled defconfig allows relevant folks to
enable on a need basis
counter to counter: what do you do when a user reports
an issue in a release and you'd want to debug it with
ETM on his platform other than doing a rebuild?
b) mostly a debug support -> only for blokes using ETM/JTAG interfaces -
not everyone can afford these (no offense to openOCD guys - but they are
still a bit away from being able to debug kernel yet on OMAP)..
counter and counter to counter - just like previous point
c) easy mechanism to enable/disable the path runtime
counter: defconfig rebuild is not *that difficult*
counter to counter: sysfs is easier and faster, saves
developer time == money
for defconfig:
a) defconfig restricts un-informed users to not mess with something they
should'nt use in the first place
counter: -EINVAL
b) defconfig removes the entire code structure out - saving on space of
save and restore memory + code path
counter: sysfs option could be wrapped within a defconfig to do exactly
the same.
c) what do you do if you need to use ETM during initial boottime (Vs
echo 1>/sys/.../etm_saverestore
counter: use save-restore sysfs entry enabled at init - a defconfig
might be helpful
--
Regards,
Nishanth Menon
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