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 using struct firmware_ops
struct firmware_ops {
/*
* Enters CPU idle mode
*/
int (*do_idle)(void);
/*
* Sets boot address of specified physical CPU
*/
int (*set_cpu_boot_addr)(int cpu, unsigned long boot_addr);
/*
* Boots specified physical CPU
*/
int (*cpu_boot)(int cpu);
/*
* Initializes L2 cache
*/
int (*l2x0_init)(void);
};
and then registered with register_firmware_ops function
void register_firmware_ops(const struct firmware_ops *ops)
the ops pointer must be non-NULL.
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);