arch: arm/xen: add putc() for debugging

This new function, xen_debug_putc(), is intended to be used to
enable CONFIG_DEBUG_UART on xen guest.

Please note that the underlying functionality in Xen is available
only when Xen is configured with !NDEBUG but is much simpler than
a generic HYPERVISOR_console_io().

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
This commit is contained in:
AKASHI Takahiro 2020-10-15 13:25:14 +09:00 committed by Tom Rini
parent 18426bf022
commit 3a51b2a2c3

View File

@ -19,4 +19,10 @@ int HYPERVISOR_sched_op(int cmd, void *arg);
int HYPERVISOR_event_channel_op(int cmd, void *arg);
unsigned long HYPERVISOR_hvm_op(int op, void *arg);
int HYPERVISOR_memory_op(unsigned int cmd, void *arg);
static inline void xen_debug_putc(int c)
{
register int v __asm__ ("x0") = c;
__asm__ __volatile__("hvc 0xfffe" : "=r" (v) : "0" (v));
}
#endif /* _ASM_ARM_XEN_HYPERCALL_H */