From: Arthur Heymans arthur@aheymans.xyz
Currently this driver is loaded if the DMI string matches coreboot and has a proper smi_command in the ACPI FADT table, but a GSMI handler in SMM is an optional feature in coreboot.
So probe for a SMM GSMI handler before initializing the driver. If the smihandler leaves the calling argument in %eax in the SMM save state untouched that generally means the is no handler for GSMI.
Signed-off-by: Arthur Heymans arthur@aheymans.xyz --- drivers/firmware/google/gsmi.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/drivers/firmware/google/gsmi.c b/drivers/firmware/google/gsmi.c index 974c769b75cf..a3eaa9f41125 100644 --- a/drivers/firmware/google/gsmi.c +++ b/drivers/firmware/google/gsmi.c @@ -746,6 +746,7 @@ MODULE_DEVICE_TABLE(dmi, gsmi_dmi_table); static __init int gsmi_system_valid(void) { u32 hash; + u16 cmd, result;
if (!dmi_check_system(gsmi_dmi_table)) return -ENODEV; @@ -780,6 +781,23 @@ static __init int gsmi_system_valid(void) return -ENODEV; }
+ /* Test the smihandler with a bogus command. If it leaves the + * calling argument in %ax untouched, there is no handler for + * GSMI commands. + */ + cmd = GSMI_CALLBACK | 0xff << 8; + asm volatile ( + "outb %%al, %%dx\n\t" + : "=a" (result) + : "0" (cmd), + "d" (acpi_gbl_FADT.smi_command) + : "memory", "cc" + ); + if (cmd == result) { + pr_info("gsmi: no gsmi handler in firmware\n"); + return -ENODEV; + } + /* Found */ return 0; }