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/* SPDX-License-Identifier: GPL-2.0-only */
#include <stdint.h>
#include <cpu/x86/smm.h>
/*
* Call the APMC SMI handler that resides in SMM. First, the command and sub-command are stored
* in eax, and the argument pointer is stored in ebx, then the command byte is written to the
* APMC IO port to trigger the SMI. The APMC SMI handler then reads the command from the APMC
* IO port and the contents of eax and ebx from the SMM state save area.
*
* static inline because the resulting assembly is often smaller than
* the call sequence due to constant folding.
*/
static inline u32 call_smm(u8 cmd, u8 subcmd, void *arg)
{
const uint16_t apmc_port = pm_acpi_smi_cmd_port();
u32 res = 0;
__asm__ __volatile__ (
"outb %%al, %%dx"
: "=a" (res)
: "a" ((subcmd << 8) | cmd),
"b" (arg),
"d" (apmc_port)
: "memory");
return res;
}
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