Re: [PATCH] i2c: ismt: Provide a DMA buffer for Interrupt Cause Logging

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Sat, May 21, 2022 at 12:53:57PM +0200, Wolfram Sang wrote:
> On Wed, Apr 27, 2022 at 01:19:10PM +0300, Mika Westerberg wrote:
> > Before sending a MSI the hardware writes information pertinent to the
> > interrupt cause to a memory location pointed by SMTICL register. This
> > memory holds three double words where the least significant bit tells
> > whether the interrupt cause of master/target/error is valid. The driver
> > does not use this but we need to set it up because otherwise it will
> > perform DMA write to the default address (0) and this will cause an
> > IOMMU fault such as below:
> > 
> >   DMAR: DRHD: handling fault status reg 2
> >   DMAR: [DMA Write] Request device [00:12.0] PASID ffffffff fault addr 0
> >         [fault reason 05] PTE Write access is not set
> > 
> > To prevent this from happening, provide a proper DMA buffer for this
> > that then gets mapped by the IOMMU accordingly.
> > 
> > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> 
> No maintainer response so far, but given this looks like an important
> bugfix and you guys are all from Intel as well, I'll apply it this time.
> 
> Applied to for-current, thanks!

Thanks!