This parameter can only be set before the module is loaded (e.g. by
passing i2c_i801.block_acpi=1 on the kernel command line).
Signed-off-by: Alex Henrie <alexh@xxxxxxxxxxx>
---
drivers/i2c/busses/i2c-i801.c | 63 +++++++++++++++++++++++++++--------
1 file changed, 49 insertions(+), 14 deletions(-)
diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 41446f9cc52d..615fd1185b61 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -288,6 +288,11 @@ struct i801_priv {
* ACPI AML use. Protected by acpi_lock.
*/
bool acpi_reserved;
+ /*
+ * If set to true ACPI AML tried to use SMBus but block_acpi was
+ * set. Protected by acpi_lock.
+ */
+ bool acpi_blocked;
struct mutex acpi_lock;
};
@@ -320,6 +325,11 @@ MODULE_PARM_DESC(disable_features, "Disable selected driver features:\n"
"\t\t 0x10 don't use interrupts\n"
"\t\t 0x20 disable SMBus Host Notify ");
+static bool block_acpi;
+module_param(block_acpi, bool, S_IRUGO);
+MODULE_PARM_DESC(block_acpi, "Prevent ACPI AML from accessing SMBus. "
+ "[0] = allow ACPI access, 1 = deny ACPI access");
+
/* Make sure the SMBus host is ready to start transmitting.
Return 0 if it is, -EBUSY if it is not. */
static int i801_check_pre(struct i801_priv *priv)
@@ -1616,23 +1626,48 @@ i801_acpi_io_handler(u32 function, acpi_physical_address address, u32 bits,
acpi_status status;
/*
- * Once BIOS AML code touches the OpRegion we warn and inhibit any
- * further access from the driver itself. This device is now owned
- * by the system firmware.
+ * If BIOS AML code tries to touches the OpRegion we have two options:
+ * Warn and inhibit any further access from the driver, or warn and
+ * inhibit all access from the BIOS.
*/
mutex_lock(&priv->acpi_lock);
- if (!priv->acpi_reserved && i801_acpi_is_smbus_ioport(priv, address)) {
- priv->acpi_reserved = true;
-
- dev_warn(&pdev->dev, "BIOS is accessing SMBus registers\n");
- dev_warn(&pdev->dev, "Driver SMBus register access inhibited\n");
-
- /*
- * BIOS is accessing the host controller so prevent it from
- * suspending automatically from now on.
- */
- pm_runtime_get_sync(&pdev->dev);
+ if (i801_acpi_is_smbus_ioport(priv, address)) {
+ if (block_acpi) {
+ /*
+ * Refuse to allow the BIOS to use SMBus. SMBus does
+ * have a lock bit in the status register that in theory
+ * can be used to safely share the SMBus between the
+ * BIOS and the kernel, but some badly behaved BIOS
+ * implementations don't use it. In that case, the only
+ * way to ensure continued safe access from the driver
+ * is to cripple the BIOS.
+ */
+ if (!priv->acpi_blocked) {
+ dev_warn(&pdev->dev,
+ "BIOS tried to access SMBus registers\n");
+ dev_warn(&pdev->dev,
+ "BIOS SMBus register access inhibited\n");
+ priv->acpi_blocked = true;
+ }
+ mutex_unlock(&priv->acpi_lock);
+ return -EPERM;
+ }
+ if (!priv->acpi_reserved) {
+ /* This device is now owned by the system firmware. */
+ priv->acpi_reserved = true;
+
+ dev_warn(&pdev->dev,
+ "BIOS is accessing SMBus registers\n");
+ dev_warn(&pdev->dev,
+ "Driver SMBus register access inhibited\n");
+
+ /*
+ * BIOS is accessing the host controller so prevent it
+ * from suspending automatically from now on.
+ */
+ pm_runtime_get_sync(&pdev->dev);
+ }
}
if ((function & ACPI_IO_MASK) == ACPI_READ)
--
2.34.1
