[PATCH v11 12/17] ARM64: ACPI: Check if it runs on Xen to enable or disable ACPI

On Wed, Apr 20, 2016 at 10:34:41AM +0100, Stefano Stabellini wrote:

Hello Mark,

do you think that this patch addresses your previous comments
(http://marc.info/?l=devicetree&m=145926913008544&w=2) appropriately?

Thanks,

Stefano

On Thu, 7 Apr 2016, Shannon Zhao wrote:

quoted

From: Shannon Zhao <redacted>

When it's a Xen domain0 booting with ACPI, it will supply a /chosen and
a /hypervisor node in DT. So check if it needs to enable ACPI.

Signed-off-by: Shannon Zhao <redacted>
Reviewed-by: Stefano Stabellini <redacted>
Acked-by: Hanjun Guo <redacted>
---
 arch/arm64/kernel/acpi.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index d1ce8e2..57ee317 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c

@@ -67,10 +67,15 @@ static int __init dt_scan_depth1_nodes(unsigned long node,
 {
 	/*
 	 * Return 1 as soon as we encounter a node at depth 1 that is
-	 * not the /chosen node.
+	 * not the /chosen node, or /hypervisor node with compatible
+	 * string "xen,xen".
 	 */
-	if (depth == 1 && (strcmp(uname, "chosen") != 0))
-		return 1;
+	if (depth == 1 && (strcmp(uname, "chosen") != 0)) {
+		if (strcmp(uname, "hypervisor") != 0 ||
+		    !of_flat_dt_is_compatible(node, "xen,xen"))
+			return 1;
+	}
+
 	return 0;
 }

Is the duplicate node checking logic I mentioned in that review gone?
i.e. do we not need an is_xen_node() helper?

Additionally, IMO, this would be easier to follow without the nested
conditionals, e.g.

static int __init dt_scan_depth1_nodes(unsigned long node,
				       const char *uname, int depth,
				       void *data)
{
	/*
	 * Ignore anything not directly under the root node; we'll
	 * catch its parent instead.
	 */
	if (depth != 1)
		return 0;

	if (strcmp(uname, "chosen") == 0)
		return 0;

	if (strcmp(uname, "hypervisor") == 0 &&
	    of_flat_dt_is_compatible(node, "xen,xen"))
		return 0;

	/*
	 * This node at depth 1 is neither a chosen node nor a xen node,
	 * which we do not expect.
	 */
	return 1;
}

Otherwise, this looks fine to me. FWIW, either way:

Acked-by: Mark Rutland <mark.rutland@arm.com>

As this is core arm64 code, I believe you'll need acks from Catalin
and/or Will (and likewise for patch 15), unless I've missed those.

Thanks,
Mark.

quoted

@@ -184,7 +189,8 @@ void __init acpi_boot_table_init(void)
 	/*
 	 * Enable ACPI instead of device tree unless
 	 * - ACPI has been disabled explicitly (acpi=off), or
-	 * - the device tree is not empty (it has more than just a /chosen node)
+	 * - the device tree is not empty (it has more than just a /chosen node,
+	 *   and a /hypervisor node when running on Xen)
 	 *   and ACPI has not been force enabled (acpi=force)
 	 */
 	if (param_acpi_off ||

-- 
2.0.4