Hi Andrew,
On Tue, Jul 30, 2019 at 01:51:51PM +0100, Andrew Murray wrote:
Some hardware will ignore bit TRCPDCR.PU which is used to signal to hardware that power should not be removed from the trace unit. Let's mitigate against this by conditionally saving and restoring the trace unit state when the CPU enters low power states.
This patchset introduces a firmware property named 'arm,coresight-needs-save-restore' - when this is present the hardware state will be conditionally saved and restored.
A module parameter 'pm_save_enable' is also introduced which can be configured to override the firmware property.
The hardware state is only ever saved and restored when a self-hosted coresight is in use.
Changes since v3:
Only save/restore when self-hosted is being used and detect this without relying on the coresight registers (which may not be available)
Only allocate memory for etmv4_save_state at probe time when configuration indicates it may be used
Set pm_save_enable param to 0444 such that it is static after boot
Save/restore TRCPDCR
Add missing comments to struct etm4_drvdata documentation
Rebased onto coresight/next (8f1f9857)
Changes since v2:
Move the PM notifier block from drvdata to file static
Add section names to document references
Add additional information to commit messages
Remove trcdvcvr and trcdvcmr from saved state and add a comment to describe why
Ensure TRCPDCR_PU is set after restore and add a comment to explain why we bother toggling TRCPDCR_PU on save/restore
Reword the pm_save_enable options and add comments
Miscellaneous style changes
Move device tree binding documentation to its own patch
Changes since v1:
Rebased onto coresight/next
Correcly pass bit number rather than BIT macro to coresight_timeout
Abort saving state if a timeout occurs
Fix completely broken pm_notify handling and unregister handler on error
Use state_needs_restore to ensure state is restored only once
Add module parameter description to existing boot_enable parameter and use module_param instead of module_param_named
Add firmware bindings for coresight-needs-save-restore
Rename 'disable_pm_save' to 'pm_save_enable' which allows for disabled, enabled or firmware
Update comment on etm4_os_lock, it incorrectly indicated that the code unlocks the trace registers
Add comments to explain use of OS lock during save/restore
Fix incorrect error description whilst waiting for PM stable
Add WARN_ON_ONCE when cpu isn't as expected during save/restore
Various updates to commit messages
Andrew Murray (6): coresight: etm4x: remove superfluous setting of os_unlock coresight: etm4x: use explicit barriers on enable/disable coresight: etm4x: use module_param instead of module_param_named coresight: etm4x: improve clarity of etm4_os_unlock comment
I have picked up the first 4 patches, so no need to send them with your next revision. Note that for patch 2/6 I have removed the "stable" tag as the patch doesn't apply to any of the stable tree. Since I have another one like that in my tree I will rework both patches and send them directly to Greg for stable consideration.
Thanks, Mathieu
coresight: etm4x: save/restore state across CPU low power states dt-bindings: arm: coresight: Add support for coresight-needs-save-restore
.../devicetree/bindings/arm/coresight.txt | 3 + drivers/hwtracing/coresight/coresight-etm4x.c | 346 +++++++++++++++++- drivers/hwtracing/coresight/coresight-etm4x.h | 64 ++++ 3 files changed, 406 insertions(+), 7 deletions(-)
-- 2.21.0