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 Signed-off-by: Patrick Rudolph patrick.rudolph@9elements.com --- drivers/firmware/google/gsmi.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
diff --git a/drivers/firmware/google/gsmi.c b/drivers/firmware/google/gsmi.c index 974c769b75cf..5b2011ebbe26 100644 --- a/drivers/firmware/google/gsmi.c +++ b/drivers/firmware/google/gsmi.c @@ -76,6 +76,7 @@ #define GSMI_CMD_LOG_S0IX_RESUME 0x0b #define GSMI_CMD_CLEAR_CONFIG 0x20 #define GSMI_CMD_HANDSHAKE_TYPE 0xC1 +#define GSMI_CMD_RESERVED 0xff
/* Magic entry type for kernel events */ #define GSMI_LOG_ENTRY_TYPE_KERNEL 0xDEAD @@ -746,6 +747,7 @@ 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 +782,23 @@ 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 | GSMI_CMD_RESERVED << 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; }