From 772742a6c7ea4612fe043353531e6435ed33e719 Mon Sep 17 00:00:00 2001 From: "Suzuki K. Poulose" Date: Wed, 18 Mar 2015 12:24:40 +0000 Subject: arm-cci: Get rid of secure transactions for PMU driver Avoid secure transactions while probing the CCI PMU. The existing code makes use of the Peripheral ID2 (PID2) register to determine the revision of the CCI400, which requires a secure transaction. This puts a limitation on the usage of the driver on systems running non-secure Linux(e.g, ARM64). Updated the device-tree binding for cci pmu node to add the explicit revision number for the compatible field. The supported strings are : arm,cci-400-pmu,r0 arm,cci-400-pmu,r1 arm,cci-400-pmu - DEPRECATED. See NOTE below NOTE: If the revision is not mentioned, we need to probe the cci revision, which could be fatal on a platform running non-secure. We need a reliable way to know if we can poke the CCI registers at runtime on ARM32. We depend on 'mcpm_is_available()' when it is available. mcpm_is_available() returns true only when there is a registered driver for mcpm. Otherwise, we assume that we don't have secure access, and skips probing the revision number(ARM64 case). The MCPM should figure out if it is safe to access the CCI. Unfortunately there isn't a reliable way to indicate the same via dtb. This patch doesn't address/change the current situation. It only deals with the CCI-PMU, leaving the assumptions about the secure access as it has been, prior to this patch. Cc: devicetree@vger.kernel.org Cc: Punit Agrawal Tested-by: Sudeep Holla Acked-by: Nicolas Pitre Acked-by: Mark Rutland Signed-off-by: Suzuki K. Poulose Signed-off-by: Will Deacon --- Documentation/devicetree/bindings/arm/cci.txt | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'Documentation/devicetree/bindings/arm/cci.txt') diff --git a/Documentation/devicetree/bindings/arm/cci.txt b/Documentation/devicetree/bindings/arm/cci.txt index f28d82bbbc56..3c5c631328d3 100644 --- a/Documentation/devicetree/bindings/arm/cci.txt +++ b/Documentation/devicetree/bindings/arm/cci.txt @@ -94,8 +94,11 @@ specific to ARM. - compatible Usage: required Value type: - Definition: must be "arm,cci-400-pmu" - + Definition: Must contain one of: + "arm,cci-400-pmu,r0" + "arm,cci-400-pmu,r1" + "arm,cci-400-pmu" - DEPRECATED, permitted only where OS has + secure acces to CCI registers - reg: Usage: required Value type: Integer cells. A register entry, expressed -- cgit v1.2.3