Re: [PATCH] pci: designware: Set DMA_BYPASS bit in outbound IATU CTRL2 register

[Sumit Kumar <sumit.kumar@oss.qualcomm.com>]

On 9/2/2026 9:47 PM, Manivannan Sadhasivam wrote:
> On Wed, Sep 02, 2026 at 08:44:57PM +0530, Krishna Chaitanya Chundru wrote:
>>
>> On 9/2/2026 7:37 PM, Manivannan Sadhasivam wrote:
>>> On Wed, Aug 26, 2026 at 02:41:20PM +0530, Sumit Kumar wrote:
>>>> Outbound IATU apertures are configured with local device-side addresses.
>>>> When DMA engine transactions use destination addresses which fall within
>>>> an outbound IATU aperture range, they get unintentionally translated by
>>>> the IATU, causing the wrong address to be sent on the PCIe link.
>>>> This results in data corruption or IOMMU errors at the host if the
>>>> translated address is not mapped.
>>>>
>>> Why are you using the same device address in both DMA and iATU mapping? This
>>> sounds like a mapping problem that you should fix instead.
>> issue happens, when host address(DMA destination address) matches with the
>> internal iova address programmed in iATU src address.
>> As we can cannot address in both,  we need to program iATU in DMA bypass mode,
>> so DMA transcations will not go through iATU window.
>>
> This needs to be explained clearly in the commit message with an example
> matching the DWC terminologies such as 'Target Address Registers'.
>
> - Mani
>
updated in v2.
- Sumit