linux-kernel - [PATCH 1/2] [PCI] Check that MWI bit really did get set

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Date:	Fri, 06 Oct 2006 13:05:18 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Val Henson <val_henson@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...e.de>
Cc:	netdev@...r.kernel.org, linux-pci@...ey.karlin.mff.cuni.cz,
	linux-kernel@...r.kernel.org, Matthew Wilcox <matthew@....cx>
Subject: [PATCH 1/2] [PCI] Check that MWI bit really did get set

Since some devices may not implement the MWI bit, we should check that
the write did set it and return an error if it didn't.

Signed-off-by: Matthew Wilcox <matthew@....cx>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index a544997..3d041f4 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -900,13 +900,17 @@ #endif
 		return rc;
 
 	pci_read_config_word(dev, PCI_COMMAND, &cmd);
-	if (! (cmd & PCI_COMMAND_INVALIDATE)) {
-		pr_debug("PCI: Enabling Mem-Wr-Inval for device %s\n", pci_name(dev));
-		cmd |= PCI_COMMAND_INVALIDATE;
-		pci_write_config_word(dev, PCI_COMMAND, cmd);
-	}
-	
-	return 0;
+	if (cmd & PCI_COMMAND_INVALIDATE)
+		return 0;
+
+	pr_debug("PCI: Enabling Mem-Wr-Inval for device %s\n", pci_name(dev));
+	cmd |= PCI_COMMAND_INVALIDATE;
+	pci_write_config_word(dev, PCI_COMMAND, cmd);
+
+	/* read result from hardware (in case bit refused to enable) */
+	pci_read_config_word(dev, PCI_COMMAND, &cmd);
+
+	return (cmd & PCI_COMMAND_INVALIDATE) ? 0 : -EINVAL;
 }
 
 /**
-
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