From: patrick.rudolph@9elements.com
To: linux-kernel@vger.kernel.org
Cc: coreboot@coreboot.org, Arthur Heymans <arthur@aheymans.xyz>,
Patrick Rudolph <patrick.rudolph@9elements.com>,
Allison Randal <allison@lohutok.net>,
Alexios Zavras <alexios.zavras@intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH v3 3/3] firmware: google: Probe for a GSMI handler in firmware
Date: Mon, 18 Nov 2019 11:19:31 +0100 [thread overview]
Message-ID: <20191118101934.22526-4-patrick.rudolph@9elements.com> (raw)
In-Reply-To: <20191118101934.22526-1-patrick.rudolph@9elements.com>
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>
---
-v2:
Add missing s-o-b and add define for reserved command.
-v3:
No changes.
---
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;
}
--
2.21.0
prev parent reply other threads:[~2019-11-18 10:20 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-18 10:19 [PATCH v3 0/3] firmware: google: Fix minor bugs patrick.rudolph
2019-11-18 10:19 ` [PATCH v3 1/3] firmware: google: Release devices before unregistering the bus patrick.rudolph
2019-11-18 10:19 ` [PATCH v3 2/3] firmware: google: Unregister driver_info on failure and exit in gsmi patrick.rudolph
2019-11-18 10:19 ` patrick.rudolph [this message]
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