Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761780AbdLSKSk (ORCPT ); Tue, 19 Dec 2017 05:18:40 -0500 Received: from foss.arm.com ([217.140.101.70]:34506 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761763AbdLSKSg (ORCPT ); Tue, 19 Dec 2017 05:18:36 -0500 Date: Tue, 19 Dec 2017 10:19:18 +0000 From: Lorenzo Pieralisi To: Niklas Cassel Cc: Jingoo Han , Joao Pinto , Bjorn Helgaas , Niklas Cassel , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 01/18] PCI: dwc: Use the DMA-API to get the MSI address Message-ID: <20171219101918.GA18921@red-moon> References: <20171120133222.27771-1-niklas.cassel@axis.com> <20171120133222.27771-2-niklas.cassel@axis.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171120133222.27771-2-niklas.cassel@axis.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3331 Lines: 92 On Mon, Nov 20, 2017 at 02:32:04PM +0100, Niklas Cassel wrote: > Use the DMA-API to get the MSI address. This address will be written to > our PCI config space and to the register which determines which AXI > address the DWC IP will spoof for incoming MSI irqs. > > Since it is a PCIe endpoint device, rather than the CPU, that is supposed > to write to the MSI address, the proper way to get the MSI address is by > using the DMA API, not by using virt_to_phys(). > > Using virt_to_phys() might work on some systems, but using the DMA API > should work on all systems. > > This is essentially the same thing as allocating a buffer in a driver > to which the endpoint will write to. To do this, we use the DMA API. > > Signed-off-by: Niklas Cassel > --- > drivers/pci/dwc/pcie-designware-host.c | 15 ++++++++++++--- > drivers/pci/dwc/pcie-designware.h | 3 ++- > 2 files changed, 14 insertions(+), 4 deletions(-) > > diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c > index 81e2157a7cfb..33b52fe98a01 100644 > --- a/drivers/pci/dwc/pcie-designware-host.c > +++ b/drivers/pci/dwc/pcie-designware-host.c > @@ -83,10 +83,19 @@ irqreturn_t dw_handle_msi_irq(struct pcie_port *pp) > > void dw_pcie_msi_init(struct pcie_port *pp) > { > + struct dw_pcie *pci = to_dw_pcie_from_pp(pp); > + struct device *dev = pci->dev; > + struct page *page; > u64 msi_target; > > - pp->msi_data = __get_free_pages(GFP_KERNEL, 0); > - msi_target = virt_to_phys((void *)pp->msi_data); > + page = alloc_page(GFP_KERNEL | GFP_DMA32); See this thread about GFP_DMA32: https://patchwork.ozlabs.org/patch/834864/ I need to look back at this set earlier versions, I do not know why you change the allocation flags but GFP_DMA32 may not provide what you need - I think you should either remove it or provide a justification for it given the discussion above. Lorenzo > + pp->msi_data = dma_map_page(dev, page, 0, PAGE_SIZE, DMA_FROM_DEVICE); > + if (dma_mapping_error(dev, pp->msi_data)) { > + dev_err(dev, "failed to map MSI data\n"); > + __free_page(page); > + return; > + } > + msi_target = (u64)pp->msi_data; > > /* program the msi_data */ > dw_pcie_wr_own_conf(pp, PCIE_MSI_ADDR_LO, 4, > @@ -187,7 +196,7 @@ static void dw_msi_setup_msg(struct pcie_port *pp, unsigned int irq, u32 pos) > if (pp->ops->get_msi_addr) > msi_target = pp->ops->get_msi_addr(pp); > else > - msi_target = virt_to_phys((void *)pp->msi_data); > + msi_target = (u64)pp->msi_data; > > msg.address_lo = (u32)(msi_target & 0xffffffff); > msg.address_hi = (u32)(msi_target >> 32 & 0xffffffff); > diff --git a/drivers/pci/dwc/pcie-designware.h b/drivers/pci/dwc/pcie-designware.h > index e5d9d77b778e..ecdede68522a 100644 > --- a/drivers/pci/dwc/pcie-designware.h > +++ b/drivers/pci/dwc/pcie-designware.h > @@ -14,6 +14,7 @@ > #ifndef _PCIE_DESIGNWARE_H > #define _PCIE_DESIGNWARE_H > > +#include > #include > #include > #include > @@ -168,7 +169,7 @@ struct pcie_port { > const struct dw_pcie_host_ops *ops; > int msi_irq; > struct irq_domain *irq_domain; > - unsigned long msi_data; > + dma_addr_t msi_data; > DECLARE_BITMAP(msi_irq_in_use, MAX_MSI_IRQS); > }; > > -- > 2.14.2 >