On 21/07/16 14:34, Rafael J. Wysocki wrote:

On Tuesday, July 19, 2016 06:52:54 PM Sudeep Holla wrote:

quoted

ACPI 6.0 introduced an optional object _LPI that provides an alternate
method to describe Low Power Idle states. It defines the local power
states for each node in a hierarchical processor topology. The OSPM can
use _LPI object to select a local power state for each level of processor
hierarchy in the system. They used to produce a composite power state
request that is presented to the platform by the OSPM.

Since multiple processors affect the idle state for any non-leaf hierarchy
node, coordination of idle state requests between the processors is
required. ACPI supports two different coordination schemes: Platform
coordinated and  OS initiated.

This patch adds initial support for Platform coordination scheme of LPI.

Cc: "Rafael J. Wysocki" <redacted>
Signed-off-by: Sudeep Holla <redacted>
---
 drivers/acpi/bus.c              |  14 +-
 drivers/acpi/processor_driver.c |   2 +-
 drivers/acpi/processor_idle.c   | 462 +++++++++++++++++++++++++++++++++++-----
 include/acpi/processor.h        |  24 ++-
 include/linux/acpi.h            |   4 +
 5 files changed, 446 insertions(+), 60 deletions(-)

[cut]

quoted

+static int acpi_processor_get_lpi_info(struct acpi_processor *pr)
+{
+	int ret, i;
+	acpi_status status;
+	acpi_handle handle = pr->handle, pr_ahandle;
+	struct acpi_device *d = NULL;
+	struct acpi_lpi_states_array info[2], *tmp, *prev, *curr;
+
+	if (!osc_pc_lpi_support_confirmed)
+		return -EOPNOTSUPP;
+
+	if (!acpi_has_method(handle, "_LPI"))
+		return -EINVAL;
+
+	flat_state_cnt = 0;
+	prev = &info[0];
+	curr = &info[1];
+	handle = pr->handle;
+	ret = acpi_processor_evaluate_lpi(handle, prev);
+	if (ret)
+		return ret;
+	flatten_lpi_states(pr, prev, NULL);
+
+	while (ACPI_SUCCESS(status = acpi_get_parent(handle, &pr_ahandle))) {

I should have mentioned that earlier, but forgot, sorry about that.

Assignments under while () etc are generally discouraged as (a) error-prone
and (b) confusing to static analysis tools.

So I'd do

	status = acpi_get_parent(handle, &pr_ahandle);
	while (ACPI_SUCCESS(status)) {

Sure, will update accordingly.

quoted

+		acpi_bus_get_device(pr_ahandle, &d);
+		handle = pr_ahandle;
+
+		if (strcmp(acpi_device_hid(d), ACPI_PROCESSOR_CONTAINER_HID))
+			break;
+
+		/* can be optional ? */
+		if (!acpi_has_method(handle, "_LPI"))
+			break;
+
+		ret = acpi_processor_evaluate_lpi(handle, curr);
+		if (ret)
+			break;
+
+		/* flatten all the LPI states in this level of hierarchy */
+		flatten_lpi_states(pr, curr, prev);
+
+		tmp = prev, prev = curr, curr = tmp;

		status = acpi_get_parent(handle, &pr_ahandle);

quoted

+	}
+

OK

Apart from this the patch looks OK to me, so please only update this one
and I'll queue up the series.

Thanks, will do it shortly.

Also I found a bug in my testing creating some fake tables to test this
non-recursive logic. I have missed a pointer update in the inner loop. I
will include the below one liner in the update.


-->8

diff --git i/drivers/acpi/processor_idle.c w/drivers/acpi/processor_idle.c
index fced1df535bd..c8800b55268d 100644
--- i/drivers/acpi/processor_idle.c
+++ w/drivers/acpi/processor_idle.c

@@ -1142,6 +1142,7 @@ static int flatten_lpi_states(struct 

acpi_processor *pr,
                             combine_lpi_states(p, t, flpi)) {
                                 stash_composite_state(curr_level, flpi);
                                 flat_state_cnt++;
+                               flpi++;
                         }
                 }
         }

-- 
Regards,
Sudeep