linux-kernel - [PATCH V2] PCI/MSI: Set device flag indicating only 32-bit MSI support

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Date:   Tue, 24 Nov 2020 16:20:35 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <bhelgaas@...gle.com>, <lorenzo.pieralisi@....com>,
        <thierry.reding@...il.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 V2] PCI/MSI: Set device flag indicating only 32-bit MSI support

There are devices (Ex:- Marvell SATA controller) that don't support
64-bit MSIs and the same is advertised through their MSI capability
register. Set no_64bit_msi flag explicitly for such devices in the
MSI setup code so that the msi_verify_entries() API would catch
if the MSI arch code tries to use 64-bit MSI.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
V2:
* Addressed Bjorn's comment and changed the error message

 drivers/pci/msi.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index d52d118979a6..8de5ba6b4a59 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -581,10 +581,12 @@ msi_setup_entry(struct pci_dev *dev, int nvec, struct irq_affinity *affd)
 	entry->msi_attrib.multi_cap	= (control & PCI_MSI_FLAGS_QMASK) >> 1;
 	entry->msi_attrib.multiple	= ilog2(__roundup_pow_of_two(nvec));
 
-	if (control & PCI_MSI_FLAGS_64BIT)
+	if (control & PCI_MSI_FLAGS_64BIT) {
 		entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_64;
-	else
+	} else {
 		entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_32;
+		dev->no_64bit_msi = 1;
+	}
 
 	/* Save the initial mask status */
 	if (entry->msi_attrib.maskbit)
@@ -602,8 +604,9 @@ static int msi_verify_entries(struct pci_dev *dev)
 	for_each_pci_msi_entry(entry, dev) {
 		if (!dev->no_64bit_msi || !entry->msg.address_hi)
 			continue;
-		pci_err(dev, "Device has broken 64-bit MSI but arch"
-			" tried to assign one above 4G\n");
+		pci_err(dev, "Device has either broken 64-bit MSI or "
+			"only 32-bit MSI support but "
+			"arch tried to assign one above 4G\n");
 		return -EIO;
 	}
 	return 0;
-- 
2.17.1