Dhruva Gole [off-list ref] writes:

On Aug 03, 2023 at 11:00:11 -0500, Andrew Davis wrote:

quoted

On 8/3/23 10:55 AM, Dhruva Gole wrote:

quoted

On Aug 03, 2023 at 10:26:32 -0500, Andrew Davis wrote:

quoted

On 8/3/23 1:42 AM, Dhruva Gole wrote:

quoted

Introduce system suspend resume calls that will allow the ti_sci
driver to support deep sleep low power mode when the user space issues a
suspend to mem.

Also, write a ti_sci_prepare_system_suspend call to be used in the driver
suspend handler to allow the system to identify the low power mode being
entered and if necessary, send TISCI_MSG_PREPARE_SLEEP with information
about the mode is being entered and the address for allocated memory for
storing the context during Deep Sleep.

We're using "pm_suspend_target_state" to map the kernel's target suspend
state to SysFW low power mode. Make sure this is available only when
CONFIG_SUSPEND is enabled.

Co-developed-by: Dave Gerlach <redacted>
Signed-off-by: Dave Gerlach <redacted>
Signed-off-by: Vibhore Vardhan <redacted>
Signed-off-by: Georgi Vlaev <redacted>
Signed-off-by: Dhruva Gole <redacted>
---
   drivers/firmware/ti_sci.c | 63 +++++++++++++++++++++++++++++++++++++++
   1 file changed, 63 insertions(+)

[..snip..]

quoted

quoted

+static int ti_sci_suspend(struct device *dev)
+{
+	struct ti_sci_info *info = dev_get_drvdata(dev);
+	int ret;
+
+	ret = ti_sci_cmd_set_io_isolation(&info->handle, TISCI_MSG_VALUE_IO_ENABLE);

After this the will the IOs be in isolation? Or does the firmware wait
until power down begins later?

 From what I understand,
IOs will be in isolation immediately

That is what I understand too, so then any device that may need to do some
external communication for its suspend will not function, this must be the
last driver _suspend() the system calls, how do you enforce that?

I will make use of .suspend_noirq callbacks in that case. Does that
sound better, or is there anything else I may not be aware of?

Using _noirq just moves the problem.  What if other drivers are also
using _noirq callbacks and run after the SCI driver?  You still cannot
guarantee ordering.

It seems to me that the IO isolation stuff is a system-wide operation,
and should probably be handled at the platform suspend_ops level
(e.g. suspend_ops->prepare_late()).   This would ensure that it runs
*after* all the driver hooks (even driver _noirq hooks.) and right
before the full suspend (or s2idle.)

Now, all that being said, I noticed that in v7, you didn't move this to
_noirq, but instead suggested that this be handled by TF-A.  I suppose
that's an option also, but my suggestion above should work also.

Kevin

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel