Messages in this thread | | | Date | Wed, 31 Aug 2022 09:54:14 +0100 | Subject | Re: [PATCH v5 20/20] PCI: dwc: Add Baikal-T1 PCIe controller support | From | Robin Murphy <> |
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On 2022-08-31 09:36, Robin Murphy wrote: > On 2022-08-29 16:28, Lorenzo Pieralisi wrote: > [...] >>> +static int bt1_pcie_add_port(struct bt1_pcie *btpci) >>> +{ >>> + struct device *dev = &btpci->pdev->dev; >>> + int ret; >>> + >>> + /* >>> + * DW PCIe Root Port controller is equipped with eDMA capable of >>> + * working with the 64-bit memory addresses. >>> + */ >>> + ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); >>> + if (ret) >>> + return ret; >> >> Is this the right place to set the DMA mask for the host controller >> embedded DMA controller (actually, the dev pointer is the _host_ >> controller device) ? >> >> How this is going to play when combined with: >> >> https://lore.kernel.org/linux-pci/1e63a581-14ae-b4b5-a5bf-ca8f09c33af6@arm.com >> >> It is getting a bit confusing. I believe the code in the link >> above sets the mask so that through the DMA API we are capable >> of getting an MSI doorbell virtual address whose physical address >> can be addressed by the endpoint; this through the DMA API. >> >> This patch is setting the DMA mask for a different reason, namely >> setting the host controller embedded DMA controller addressing >> capabilities. >> >> AFAICS - both approaches set the mask for the same device - now >> the question is about which one is legitimate and how to handle >> the other. > > Assuming the dw-edma-pcie driver is the relevant one, that already sets > its own masks on its own device, so I also don't see why this is here.
Ah, I just found the patch at [1], which further implies that this is indeed completely bogus.
Robin.
[1] https://lore.kernel.org/dmaengine/20220822185332.26149-23-Sergey.Semin@baikalelectronics.ru/
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