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Date: Mon, 12 Sep 2022 03:25:22 +0300 From: Serge Semin <fancer.lancer@...il.com> To: Robin Murphy <robin.murphy@....com> Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>, Serge Semin <Sergey.Semin@...kalelectronics.ru>, Rob Herring <robh+dt@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Bjorn Helgaas <bhelgaas@...gle.com>, Lorenzo Pieralisi <lorenzo.pieralisi@....com>, Jingoo Han <jingoohan1@...il.com>, Gustavo Pimentel <gustavo.pimentel@...opsys.com>, Krzysztof Wilczyński <kw@...ux.com>, Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>, Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>, Frank Li <Frank.Li@....com>, Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, linux-pci@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, willmcvicker@...gle.com Subject: Re: [PATCH v5 20/20] PCI: dwc: Add Baikal-T1 PCIe controller support On Wed, Aug 31, 2022 at 09:54:14AM +0100, Robin Murphy wrote: > 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. Really? Elaborate please. What you said in the comment to that patch has nothing to do with the change you comment here. -Sergey > > Robin. > > [1] https://lore.kernel.org/dmaengine/20220822185332.26149-23-Sergey.Semin@baikalelectronics.ru/
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