Re: [PATCH] ARM: tegra: Ensure entire dcache is flushed on entering LP0/1

From: Joseph Lo
Date: Sat Nov 21 2015 - 06:56:48 EST

Hi Jon,

On 11/19/2015 10:19 PM, Jon Hunter wrote:
Tegra support several low-power (LPx) states, which are:
- LP0: CPU + Core voltage off and DRAM in self-refresh
- LP1: CPU voltage off and DRAM in self-refresh
- LP2: CPU voltage off

When entering any of the above states the tegra_disable_clean_inv_dcache()
function is called to flush the dcache. The function
tegra_disable_clean_inv_dcache() will either flush the entire data cache or
up to the Level of Unification Inner Shareable (LoUIS) depending on the
value in r0. When tegra_disable_clean_inv_dcache() is called by
tegra20_sleep_core_finish() or tegra30_sleep_core_finish(), to enter LP0
and LP1 power state, the r0 register contains a physical memory address
which will not be equal to TEGRA_FLUSH_CACHE_ALL (1) and so the data cache
will be only flushed to the LoUIS. However, when
tegra_disable_clean_inv_dcache() called by tegra_sleep_cpu_finish() to
enter to LP2 power state, r0 is set to TEGRA_FLUSH_CACHE_ALL to flush the
entire dcache.

Please note that tegra20_sleep_core_finish(), tegra30_sleep_core_finish()
and tegra_sleep_cpu_finish() are called by the boot CPU once all other CPUs
have been disabled and so it seems appropriate to flush the entire cache at
this stage.

Therefore, ensure that r0 is set to TEGRA_FLUSH_CACHE_ALL when calling
tegra_disable_clean_inv_dcache() from tegra20_sleep_core_finish() and

Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>

Thanks for the fix.

Reviewed-by: Joseph Lo <josephl@xxxxxxxxxx>

Please note that I have not encountered any problems without this change
so far, but I noticed this from reviewing the suspend sequence. I have
tested this on tegra20, tegra30, tegra114 and tegra124 and verified that
suspend/resume to LP1 is working fine.

arch/arm/mach-tegra/sleep-tegra20.S | 3 +++
arch/arm/mach-tegra/sleep-tegra30.S | 3 +++
2 files changed, 6 insertions(+)

diff --git a/arch/arm/mach-tegra/sleep-tegra20.S b/arch/arm/mach-tegra/sleep-tegra20.S
index e6b684e14322..f5d19667484e 100644
--- a/arch/arm/mach-tegra/sleep-tegra20.S
+++ b/arch/arm/mach-tegra/sleep-tegra20.S
@@ -231,8 +231,11 @@ ENDPROC(tegra20_cpu_is_resettable_soon)
* tegra20_tear_down_core in IRAM
+ mov r4, r0
/* Flush, disable the L1 data cache and exit SMP */
bl tegra_disable_clean_inv_dcache
+ mov r0, r4

mov32 r3, tegra_shut_off_mmu
add r3, r3, r0
diff --git a/arch/arm/mach-tegra/sleep-tegra30.S b/arch/arm/mach-tegra/sleep-tegra30.S
index 9a2f0b051e10..16e5ff03383c 100644
--- a/arch/arm/mach-tegra/sleep-tegra30.S
+++ b/arch/arm/mach-tegra/sleep-tegra30.S
@@ -242,8 +242,11 @@ ENDPROC(tegra30_cpu_shutdown)
* tegra30_tear_down_core in IRAM
+ mov r4, r0
/* Flush, disable the L1 data cache and exit SMP */
bl tegra_disable_clean_inv_dcache
+ mov r0, r4

* Preload all the address literals that are needed for the

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