Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752107AbdFZVcq (ORCPT ); Mon, 26 Jun 2017 17:32:46 -0400 Received: from cloudserver094114.home.net.pl ([79.96.170.134]:59634 "EHLO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752037AbdFZVco (ORCPT ); Mon, 26 Jun 2017 17:32:44 -0400 From: "Rafael J. Wysocki" To: Lyude Cc: intel-gfx@lists.freedesktop.org, "Rafael J . Wysocki" , Benjamin Tissoires , Mika Westerberg , Jean Delvare , Wolfram Sang , Jean Delvare , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, Linux ACPI Subject: Re: [PATCH] i2c: i801: Allow ACPI SystemIO OpRegion to conflict harder Date: Mon, 26 Jun 2017 23:25:19 +0200 Message-ID: <7337961.XKbvYND0Ly@aspire.rjw.lan> User-Agent: KMail/4.14.10 (Linux/4.12.0-rc1+; KDE/4.14.9; x86_64; ; ) In-Reply-To: <20170626204009.32607-1-lyude@redhat.com> References: <20170626204009.32607-1-lyude@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5220 Lines: 125 On Monday, June 26, 2017 04:40:08 PM Lyude wrote: > There's quite a number of machines on the market, mainly Lenovo > ThinkPads, that make the horrible mistake in their firmware of reusing > the PCIBAR space reserved for the SMBus for things that are completely > unrelated to the SMBus controller, such as the OpRegion used for i915. > This is very bad and entirely evil, but with Lenovo's historically poor > track record of fixing their firmware, it is extremely unlikely this is > ever going to be properly fixed. > > So, while it would be nice if we could just cut off the SMBus controller > and call it a day this unfortunately breaks RMI4 mode completely for > most of the ThinkPads. Even though this behavior is extremely wrong, for > whatever reason sharing the PCIBAR between the OpRegion and SMBus seems > to be just fine. Regardless however, I think it's safe to assume that > when the BIOS accesses the PCIBAR space of the SMBus controller like > this that it's trying to get to something else that we mapped the SMBus > controller over. > > On my X1 Carbon, this assumption appears to be correct. I've traced down > the firmware accesses to being caused by the firmware mistakenly placing > the SWSCI mailbox for i915 on top of the SMBus host controller region. > And indeed, blacklisting i915 causes the firmware to never attempt to > touch this region. > > So, in order to try to workaround this and not break either SMBus or > i915, we temporarily unmap the PCI device for the SMBus controller, > do the thing that the firmware wanted to do, then remap the device and > report a firmware bug. > > Signed-off-by: Lyude > Cc: Rafael J. Wysocki > Cc: Benjamin Tissoires > Cc: Mika Westerberg > Cc: Jean Delvare > Cc: Wolfram Sang > Cc: intel-gfx@lists.freedesktop.org > --- > So: unfortunately > > a7ae81952cda (i2c: i801: Allow ACPI SystemIO OpRegion to conflict with PCI BAR) > > Seems to prevent the ThinkPad X1 Carbon 4th gen and the T460s from actually > using their SMBus controllers at all. As mentioned above, I've traced the issue > down to the firmware responding to the SWSCI by sticking data in places it > shouldn't, e.g. the SMBus registers. > > I'm entirely unsure if this patch is the correct fix for this, and wouldn't be > at all surprised if it's just as bad of a patch as I think it is ;P. So I > figured I'd send it to intel-gfx and the authors of the original version of this > patch to get their take on it and see if there might be something less hacky we > can do to fix this. It would really help to send this to linux-acpi@vger.kernel.org (as pretty much everything ACPI-related). Adding the CC and retaining the patch below for completeness. > > drivers/i2c/busses/i2c-i801.c | 41 +++++++++++++++++++++++++---------------- > 1 file changed, 25 insertions(+), 16 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c > index 6484fa6..bfbe0f9 100644 > --- a/drivers/i2c/busses/i2c-i801.c > +++ b/drivers/i2c/busses/i2c-i801.c > @@ -1406,33 +1406,42 @@ i801_acpi_io_handler(u32 function, acpi_physical_address address, u32 bits, > { > struct i801_priv *priv = handler_context; > struct pci_dev *pdev = priv->pci_dev; > + struct device *dev = &pdev->dev; > acpi_status status; > + int err; > > - /* > - * 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. > - */ > mutex_lock(&priv->acpi_lock); > > - if (!priv->acpi_reserved) { > - priv->acpi_reserved = true; > + /* > + * BIOS AML code should never actually touch the SMBus registers, > + * however crappy firmware (mainly Lenovo's) can make the mistake of > + * mapping things over the SMBus region that should definitely not be > + * there (such as the OpRegion for Intel GPUs). > + * This is extremely bad firmware behavior, but it is unlikely this will > + * ever get fixed by Lenovo. > + */ > + dev_warn_once(dev, > + FW_BUG "OpRegion overlaps with SMBus registers, working around\n"); > > - 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); > - } > + pm_runtime_get_sync(dev); > + pcim_iounmap_regions(pdev, 1 << SMBBAR); > > if ((function & ACPI_IO_MASK) == ACPI_READ) > status = acpi_os_read_port(address, (u32 *)value, bits); > else > status = acpi_os_write_port(address, (u32)*value, bits); > > + err = pcim_iomap_regions(pdev, 1 << SMBBAR, > + dev_driver_string(&pdev->dev)); > + if (err) { > + dev_err(&pdev->dev, > + FW_BUG "Failed to restore SMBus region 0x%lx-0x%Lx. SMBus is now broken.\n", > + priv->smba, > + (unsigned long long)pci_resource_end(pdev, SMBBAR)); > + priv->acpi_reserved = true; > + } > + > + pm_runtime_put(dev); > mutex_unlock(&priv->acpi_lock); > > return status; >