firmware.rst 2.3 KB

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  1. ==========================================================================
  2. Interface for registering and calling firmware-specific operations for ARM
  3. ==========================================================================
  4. Written by Tomasz Figa <t.figa@samsung.com>
  5. Some boards are running with secure firmware running in TrustZone secure
  6. world, which changes the way some things have to be initialized. This makes
  7. a need to provide an interface for such platforms to specify available firmware
  8. operations and call them when needed.
  9. Firmware operations can be specified by filling in a struct firmware_ops
  10. with appropriate callbacks and then registering it with register_firmware_ops()
  11. function::
  12. void register_firmware_ops(const struct firmware_ops *ops)
  13. The ops pointer must be non-NULL. More information about struct firmware_ops
  14. and its members can be found in arch/arm/include/asm/firmware.h header.
  15. There is a default, empty set of operations provided, so there is no need to
  16. set anything if platform does not require firmware operations.
  17. To call a firmware operation, a helper macro is provided::
  18. #define call_firmware_op(op, ...) \
  19. ((firmware_ops->op) ? firmware_ops->op(__VA_ARGS__) : (-ENOSYS))
  20. the macro checks if the operation is provided and calls it or otherwise returns
  21. -ENOSYS to signal that given operation is not available (for example, to allow
  22. fallback to legacy operation).
  23. Example of registering firmware operations::
  24. /* board file */
  25. static int platformX_do_idle(void)
  26. {
  27. /* tell platformX firmware to enter idle */
  28. return 0;
  29. }
  30. static int platformX_cpu_boot(int i)
  31. {
  32. /* tell platformX firmware to boot CPU i */
  33. return 0;
  34. }
  35. static const struct firmware_ops platformX_firmware_ops = {
  36. .do_idle = exynos_do_idle,
  37. .cpu_boot = exynos_cpu_boot,
  38. /* other operations not available on platformX */
  39. };
  40. /* init_early callback of machine descriptor */
  41. static void __init board_init_early(void)
  42. {
  43. register_firmware_ops(&platformX_firmware_ops);
  44. }
  45. Example of using a firmware operation::
  46. /* some platform code, e.g. SMP initialization */
  47. __raw_writel(__pa_symbol(exynos4_secondary_startup),
  48. CPU1_BOOT_REG);
  49. /* Call Exynos specific smc call */
  50. if (call_firmware_op(cpu_boot, cpu) == -ENOSYS)
  51. cpu_boot_legacy(...); /* Try legacy way */
  52. gic_raise_softirq(cpumask_of(cpu), 1);