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2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/arch/mips/pci/fixup-sb1250.c
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@@ -1,13 +1,11 @@
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+// SPDX-License-Identifier: GPL-2.0-or-later
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 /*
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  *	Copyright (C) 2004, 2006  MIPS Technologies, Inc.  All rights reserved.
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  *	    Author:	Maciej W. Rozycki <macro@mips.com>
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- *
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- *	This program is free software; you can redistribute it and/or
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- *	modify it under the terms of the GNU General Public License
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- *	as published by the Free Software Foundation; either version
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- *	2 of the License, or (at your option) any later version.
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+ *	Copyright (C) 2018  Maciej W. Rozycki
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  */
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+#include <linux/dma-mapping.h>
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 #include <linux/pci.h>
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 /*
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@@ -22,6 +20,57 @@
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 			quirk_sb1250_pci);
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21
 
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 /*
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+ * The BCM1250, etc. PCI host bridge does not support DAC on its 32-bit
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+ * bus, so we set the bus's DMA limit accordingly.  However the HT link
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+ * down the artificial PCI-HT bridge supports 40-bit addressing and the
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+ * SP1011 HT-PCI bridge downstream supports both DAC and a 64-bit bus
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+ * width, so we record the PCI-HT bridge's secondary and subordinate bus
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+ * numbers and do not set the limit for devices present in the inclusive
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+ * range of those.
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+ */
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+struct sb1250_bus_dma_limit_exclude {
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+	bool set;
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+	unsigned char start;
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+	unsigned char end;
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+};
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+
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+static int sb1250_bus_dma_limit(struct pci_dev *dev, void *data)
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+{
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+	struct sb1250_bus_dma_limit_exclude *exclude = data;
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+	bool exclude_this;
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+	bool ht_bridge;
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+
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+	exclude_this = exclude->set && (dev->bus->number >= exclude->start &&
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+					dev->bus->number <= exclude->end);
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+	ht_bridge = !exclude->set && (dev->vendor == PCI_VENDOR_ID_SIBYTE &&
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+				      dev->device == PCI_DEVICE_ID_BCM1250_HT);
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+
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+	if (exclude_this) {
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+		dev_dbg(&dev->dev, "not disabling DAC for device");
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+	} else if (ht_bridge) {
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+		exclude->start = dev->subordinate->number;
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+		exclude->end = pci_bus_max_busnr(dev->subordinate);
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+		exclude->set = true;
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+		dev_dbg(&dev->dev, "not disabling DAC for [bus %02x-%02x]",
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+			exclude->start, exclude->end);
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+	} else {
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+		dev_dbg(&dev->dev, "disabling DAC for device");
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+		dev->dev.bus_dma_limit = DMA_BIT_MASK(32);
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+	}
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+
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+	return 0;
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+}
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+
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+static void quirk_sb1250_pci_dac(struct pci_dev *dev)
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+{
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+	struct sb1250_bus_dma_limit_exclude exclude = { .set = false };
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+
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+	pci_walk_bus(dev->bus, sb1250_bus_dma_limit, &exclude);
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+}
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+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_SIBYTE, PCI_DEVICE_ID_BCM1250_PCI,
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+			quirk_sb1250_pci_dac);
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+
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+/*
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  * The BCM1250, etc. PCI/HT bridge reports as a host bridge.
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  */
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 static void quirk_sb1250_ht(struct pci_dev *dev)