tree dce3a88158eaea3773311d4f606713e30ceba3e9
parent e2f5fb254989398e7b8ed3e203928825ace4417c
author Sugnan Prabhu S <sugnan.prabhu.s@intel.com> 1593675143 +0530
committer Subrata Banik <subrata.banik@intel.com> 1596426290 +0000

drivers/intel/mipi_camera: Add reference counting for shared resources

This change updates the mipi_camera driver to handle shared power
resource between multiple cameras. This is achieved by adding a guard
variable and methods to manipulate the guard variable before calling
the actual platform method which enables or disables the resource.
PowerResource will call these guarded methods to enable or disable the
resource. This protects the shared resource from being enabled or
disabled multiple times while the other camera is using the resource.

Example:
Consider a platform where two cameras are sharing a GPIO resource 0xXX
and both the cameras calls enable and disable guarded methods for this
GPIO. Actual platform disable method for the GPIO is called only after
the last camera using the GPIO calls DSBx method and RESx becomes 0.

Scope (\_SB.PCI0)
{
	Name (RESx, Zero)
	Method (ENBx, 0, Serialized)
	{
		If ((RESx == Zero))
		{
			\_SB.PCI0.STXS (0xXX)
		}

		RESx++
	}

	Method (DSBx, 0, Serialized)
	{
		If ((RESx > Zero))
		{
			RESx--
		}

		If ((RESx == Zero))
		{
			\_SB.PCI0.CTXS (0xXX)
		}
	}
}

Change-Id: I1468459d5bbb2fb07bef4e0590c96dd4dbab0d9c
Signed-off-by: Sugnan Prabhu S <sugnan.prabhu.s@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43003
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>