linux-kernel - [PATCH] PCI: dwc: Set 32-bit DMA mask for MSI target address allocation

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Date:   Tue, 17 Nov 2020 22:23:12 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <jingoohan1@...il.com>, <gustavo.pimentel@...opsys.com>,
        <lorenzo.pieralisi@....com>, <bhelgaas@...gle.com>,
        <robh@...nel.org>, <treding@...dia.com>, <jonathanh@...dia.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kthota@...dia.com>, <mmaddireddy@...dia.com>, <vidyas@...dia.com>,
        <sagar.tv@...il.com>
Subject: [PATCH] PCI: dwc: Set 32-bit DMA mask for MSI target address allocation

Set DMA mask to 32-bit while allocating the MSI target address so that
the address is usable for both 32-bit and 64-bit MSI capable devices.
Throw a warning if it fails to set the mask to 32-bit to alert that
devices that are only 32-bit MSI capable may not work properly.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
Given the other patch that I've pushed to the MSI sub-system
http://patchwork.ozlabs.org/project/linux-pci/patch/20201117145728.4516-1-vidyas@nvidia.com/
which is going to catch any mismatch between MSI capability (32-bit) of the
device and system's inability to allocate the required MSI target address,
I'm not sure how much sense is this patch going to be make. But, I can
certainly say that if the memory allocation mechanism gives the addresses
from 64-bit pool by default, this patch at least makes sure that MSI target
address is allocated from 32-bit pool.

 drivers/pci/controller/dwc/pcie-designware-host.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 44c2a6572199..e6a230eddf66 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -388,6 +388,14 @@ int dw_pcie_host_init(struct pcie_port *pp)
 							    dw_chained_msi_isr,
 							    pp);
 
+			ret = dma_set_mask(pci->dev, DMA_BIT_MASK(32));
+			if (!ret) {
+				dev_warn(pci->dev,
+					 "Failed to set DMA mask to 32-bit. "
+					 "Devices with only 32-bit MSI support"
+					 " may not work properly\n");
+			}
+
 			pp->msi_data = dma_map_single_attrs(pci->dev, &pp->msi_msg,
 						      sizeof(pp->msi_msg),
 						      DMA_FROM_DEVICE,
-- 
2.17.1