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Diffstat (limited to 'kernel/Documentation/arm/firmware.txt')
-rw-r--r-- | kernel/Documentation/arm/firmware.txt | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/kernel/Documentation/arm/firmware.txt b/kernel/Documentation/arm/firmware.txt new file mode 100644 index 000000000..da6713ada --- /dev/null +++ b/kernel/Documentation/arm/firmware.txt @@ -0,0 +1,70 @@ +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); |