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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
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Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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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(__pa_symbol(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);