On Wednesday, May 04, 2016 12:27:25 PM Mika Westerberg wrote:
> Many Intel systems the BIOS declares a SystemIO OpRegion below the SMBus
> PCI device as can be seen in ACPI DSDT table from Lenovo Yoga 900:
>
> Device (SBUS)
> {
> OperationRegion (SMBI, SystemIO, (SBAR << 0x05), 0x10)
> Field (SMBI, ByteAcc, NoLock, Preserve)
> {
> HSTS, 8,
> Offset (0x02),
> HCON, 8,
> HCOM, 8,
> TXSA, 8,
> DAT0, 8,
> DAT1, 8,
> HBDR, 8,
> PECR, 8,
> RXSA, 8,
> SDAT, 16
> }
>
> There are also bunch of AML methods that that the BIOS can use to access
> these fields. Most of the systems in question AML methods accessing the
> SMBI OpRegion are never used.
>
> Now, because of this SMBI OpRegion many systems fail to load the SMBus
> driver with an error looking like one below:
>
> ACPI Warning: SystemIO range 0x0000000000003040-0x000000000000305F
> conflicts with OpRegion 0x0000000000003040-0x000000000000304F
> (\_SB.PCI0.SBUS.SMBI) (20160108/utaddress-255)
> ACPI: If an ACPI driver is available for this device, you should use
> it instead of the native driver
>
> The reason is that this SMBI OpRegion conflicts with the PCI BAR used by
> the SMBus driver.
>
> It turns out that we can install a custom SystemIO address space handler
> for the SMBus device to intercept all accesses through that OpRegion. This
> allows us to share the PCI BAR with the AML code if it for some reason is
> using it. We do not expect that this OpRegion handler will ever be called
> but if it is we print a warning and prevent all access from the SMBus
> driver itself.
>
> Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> ---
> Hi,
>
> This is a second try. The first version of the patch is here:
>
> https://patchwork.ozlabs.org/patch/616120/
>
> This version inhibits all further driver access to the SMBus device when
> BIOS first time uses the conflicting OpRegion.
>
> I've tested this using MinnowBoard MAX with modified DSDT where _STA
> (device status) method tries to read from the OpRegion and it seems to
> work. Below is the modified ASL if someone wants to give it a try:
>
> Device (SBUS)
> {
> Name (_ADR, 0x001F0003) // _ADR: Address
> OperationRegion (SMBP, PCI_Config, 0x40, 0xC0)
> Field (SMBP, DWordAcc, NoLock, Preserve)
> {
> , 2,
> I2CE, 1
> }
>
> OperationRegion (SMPB, PCI_Config, 0x20, 0x04)
> Field (SMPB, DWordAcc, NoLock, Preserve)
> {
> , 5,
> SBAR, 11
> }
>
> OperationRegion (SMBI, SystemIO, (SBAR << 0x05), 0x10)
> Field (SMBI, ByteAcc, NoLock, Preserve)
> {
> HSTS, 8,
> Offset (0x02),
> HCON, 8,
> HCOM, 8,
> TXSA, 8,
> DAT0, 8,
> DAT1, 8,
> HBDR, 8,
> PECR, 8,
> RXSA, 8,
> SDAT, 16
> }
>
> Method (_STA, 0, NotSerialized)
> {
> Local0 = HSTS
> Local0 += 1
> Local1 = SDAT
> Local1 += 1
> Return (0xF)
> }
> }
>
> Basically it just does two reads from the OpRegion whenever device status
> is queried. After that accesses to the bus fails:
>
> # i2cget -y 9 0xc 0 b
> Error: Read failed
>
> drivers/i2c/busses/i2c-i801.c | 106 ++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 102 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index 5652bf6ce9be..e200cdbd2882 100644
> --- a/drivers/i2c/busses/i2c-i801.c
> +++ b/drivers/i2c/busses/i2c-i801.c
> @@ -247,6 +247,13 @@ struct i801_priv {
> struct platform_device *mux_pdev;
> #endif
> struct platform_device *tco_pdev;
> +
> + /*
> + * If set to true the host controller registers are reserved for
> + * ACPI AML use. Protected by acpi_lock.
> + */
> + bool acpi_reserved;
> + struct mutex acpi_lock;
> };
>
> #define FEATURE_SMBUS_PEC (1 << 0)
> @@ -720,6 +727,12 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr,
> int ret = 0, xact = 0;
> struct i801_priv *priv = i2c_get_adapdata(adap);
>
> + mutex_lock(&priv->acpi_lock);
> + if (priv->acpi_reserved) {
> + mutex_unlock(&priv->acpi_lock);
> + return -EPERM;
I'd return -EIO from here as that's what it looks like from the caller's perspective.
That's not a big deal, though, so
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
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