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| author | Arthur Heymans <arthur@aheymans.xyz> | 2019-11-18 11:19:31 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-01-14 21:46:48 +0100 |
| commit | e4924ee263b015cc2e397ca871d870925e2673b4 (patch) | |
| tree | d12c1388810f353196fc882be8a4a4a6b0250686 /drivers/firmware | |
| parent | c6e7af0515daca800d84b9cfa1bf19e53c4f5bc3 (diff) | |
| download | linux-e4924ee263b015cc2e397ca871d870925e2673b4.tar.bz2 | |
firmware: google: Probe for a GSMI handler in firmware
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>
Link: https://lore.kernel.org/r/20191118101934.22526-4-patrick.rudolph@9elements.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/firmware')
| -rw-r--r-- | drivers/firmware/google/gsmi.c | 19 |
1 files changed, 19 insertions, 0 deletions
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; } |