Patchwork [4/7] ARM: tegra30: common: enable csite clock

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Submitter Joseph Lo
Date Oct. 8, 2012, 10:26 a.m.
Message ID <1349691981-31038-5-git-send-email-josephl@nvidia.com>
Download mbox | patch
Permalink /patch/189975/
State Superseded, archived
Headers show

Comments

Joseph Lo - Oct. 8, 2012, 10:26 a.m.
Enable csite (debug and trace controller) clock at init to prevent it
be disabled. And this also the necessary clock for CPU be brought up or
resumed from a power-gate low power state (e.g., LP2).

Signed-off-by: Joseph Lo <josephl@nvidia.com>
---
 arch/arm/mach-tegra/common.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
Stephen Warren - Oct. 9, 2012, 10:38 p.m.
On 10/08/2012 04:26 AM, Joseph Lo wrote:
> Enable csite (debug and trace controller) clock at init to prevent it
> be disabled. And this also the necessary clock for CPU be brought up or
> resumed from a power-gate low power state (e.g., LP2).

Does it make sense to enable this clock only when entering LP2? Or do we
really need to keep it on 100% of the time?
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Joseph Lo - Oct. 11, 2012, 10:28 a.m.
On Wed, 2012-10-10 at 06:38 +0800, Stephen Warren wrote:
> On 10/08/2012 04:26 AM, Joseph Lo wrote:
> > Enable csite (debug and trace controller) clock at init to prevent it
> > be disabled. And this also the necessary clock for CPU be brought up or
> > resumed from a power-gate low power state (e.g., LP2).
> 
> Does it make sense to enable this clock only when entering LP2? Or do we
> really need to keep it on 100% of the time?

Hmmm. I am not sure does the RealView or Lauterbach ICE can still attach
to the target if the clock is not available. Or even it can be attached
but some functions of the debugger may not work. Because the CoreSight
is a very fancy debug module.

I only test it with a light weight debugger (OpenOCD). It still can work
without turning on the CoreSight clock. Maybe it just because the
openocd debugger only using the jtag interface.

Anyway, I think we need the csite always on for the developer that using
RealView or Lauterbach ICE.

Thanks,
Joseph

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Patch

diff --git a/arch/arm/mach-tegra/common.c b/arch/arm/mach-tegra/common.c
index 0b0a5f5..4a2dd98 100644
--- a/arch/arm/mach-tegra/common.c
+++ b/arch/arm/mach-tegra/common.c
@@ -104,6 +104,7 @@  static __initdata struct tegra_clk_init_table tegra30_clk_init_table[] = {
 	{ "clk_m",	NULL,		0,		true },
 	{ "pll_p",	"clk_m",	408000000,	true },
 	{ "pll_p_out1",	"pll_p",	9600000,	true },
+	{ "csite",	NULL,		0,		true },
 	{ NULL,		NULL,		0,		0},
 };
 #endif