Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / Documentation / arm / firmware.txt

diff --git a/kernel/Documentation/arm/firmware.txt b/kernel/Documentation/arm/firmware.txt
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+Interface for registering and calling firmware-specific operations for ARM.
+----
+Written by Tomasz Figa <t.figa@samsung.com>
+
+Some boards are running with secure firmware running in TrustZone secure
+world, which changes the way some things have to be initialized. This makes
+a need to provide an interface for such platforms to specify available firmware
+operations and call them when needed.
+
+Firmware operations can be specified by filling in a struct firmware_ops
+with appropriate callbacks and then registering it with register_firmware_ops()
+function.
+
+       void register_firmware_ops(const struct firmware_ops *ops)
+
+The ops pointer must be non-NULL. More information about struct firmware_ops
+and its members can be found in arch/arm/include/asm/firmware.h header.
+
+There is a default, empty set of operations provided, so there is no need to
+set anything if platform does not require firmware operations.
+
+To call a firmware operation, a helper macro is provided
+
+       #define call_firmware_op(op, ...)                               \
+               ((firmware_ops->op) ? firmware_ops->op(__VA_ARGS__) : (-ENOSYS))
+
+the macro checks if the operation is provided and calls it or otherwise returns
+-ENOSYS to signal that given operation is not available (for example, to allow
+fallback to legacy operation).
+
+Example of registering firmware operations:
+
+       /* board file */
+
+       static int platformX_do_idle(void)
+       {
+               /* tell platformX firmware to enter idle */
+               return 0;
+       }
+
+       static int platformX_cpu_boot(int i)
+       {
+               /* tell platformX firmware to boot CPU i */
+               return 0;
+       }
+
+       static const struct firmware_ops platformX_firmware_ops = {
+               .do_idle        = exynos_do_idle,
+               .cpu_boot       = exynos_cpu_boot,
+               /* other operations not available on platformX */
+       };
+
+       /* init_early callback of machine descriptor */
+       static void __init board_init_early(void)
+       {
+               register_firmware_ops(&platformX_firmware_ops);
+       }
+
+Example of using a firmware operation:
+
+       /* some platform code, e.g. SMP initialization */
+
+       __raw_writel(virt_to_phys(exynos4_secondary_startup),
+               CPU1_BOOT_REG);
+
+       /* Call Exynos specific smc call */
+       if (call_firmware_op(cpu_boot, cpu) == -ENOSYS)
+               cpu_boot_legacy(...); /* Try legacy way */
+
+       gic_raise_softirq(cpumask_of(cpu), 1);