[PATCH 24/32] powerpc: Cell "Spider" MMIO workarounds

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

This is totally untested, I just put it together quickly, but gives an
example of how the hooks can be used which is why I introduced it in
this serie. Hopefully, I'll test & fix it up properly this week.

This patch implements a workaround for a Spider PCI host bridge bug
where it doesn't enforce some of the PCI ordering rules unless some
manual manipulation of a special register is done. In order to be
fully compliant with the PCI spec, I do this on every MMIO read
operation.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

 arch/powerpc/Kconfig                         |    1 
 arch/powerpc/platforms/cell/Makefile         |    3 
 arch/powerpc/platforms/cell/io-workarounds.c |  346 +++++++++++++++++++++++++++
 3 files changed, 349 insertions(+), 1 deletion(-)

Index: linux-cell/arch/powerpc/Kconfig
===================================================================
--- linux-cell.orig/arch/powerpc/Kconfig	2006-11-08 15:18:10.000000000 +1100
+++ linux-cell/arch/powerpc/Kconfig	2006-11-09 17:29:40.000000000 +1100
@@ -468,6 +468,7 @@ config PPC_CELL_NATIVE
 	select PPC_CELL
 	select PPC_DCR_MMIO
 	select PPC_OF_PLATFORM_PCI
+	select PPC_INDIRECT_IO
 	select MPIC
 	default n
 
Index: linux-cell/arch/powerpc/platforms/cell/Makefile
===================================================================
--- linux-cell.orig/arch/powerpc/platforms/cell/Makefile	2006-11-08 15:18:10.000000000 +1100
+++ linux-cell/arch/powerpc/platforms/cell/Makefile	2006-11-08 15:21:34.000000000 +1100
@@ -1,5 +1,6 @@
 obj-$(CONFIG_PPC_CELL_NATIVE)		+= interrupt.o iommu.o setup.o \
-					   cbe_regs.o spider-pic.o pervasive.o
+					   cbe_regs.o spider-pic.o \
+					   pervasive.o io-workarounds.o
 obj-$(CONFIG_CBE_RAS)			+= ras.o
 
 ifeq ($(CONFIG_SMP),y)
Index: linux-cell/arch/powerpc/platforms/cell/io-workarounds.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-cell/arch/powerpc/platforms/cell/io-workarounds.c	2006-11-09 17:30:11.000000000 +1100
@@ -0,0 +1,346 @@
+/*
+ *  Copyright (C) 2006 Benjamin Herrenschmidt <benh@kernel.crashing.org>
+ *		       IBM, Corp.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#undef DEBUG
+
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/pci.h>
+#include <asm/io.h>
+#include <asm/machdep.h>
+#include <asm/pci-bridge.h>
+#include <asm/ppc-pci.h>
+
+
+#define SPIDER_PCI_REG_BASE		0xd000
+#define SPIDER_PCI_VCI_CNTL_STAT	0x0110
+#define SPIDER_PCI_DUMMY_READ		0x0810
+#define SPIDER_PCI_DUMMY_READ_BASE	0x0814
+
+/* Undefine that to re-enable bogus prefetch
+ *
+ * Without that workaround, the chip will do bogus prefetch past
+ * page boundary from system memory. This setting will disable that,
+ * though the documentation is unclear as to the consequences of doing
+ * so, either purely performances, or possible misbehaviour... It's not
+ * clear wether the chip can handle unaligned accesses at all without
+ * prefetching enabled.
+ *
+ * For now, things appear to be behaving properly with that prefetching
+ * disabled and IDE, possibly because IDE isn't doing any unaligned
+ * access.
+ */
+#define SPIDER_DISABLE_PREFETCH
+
+#define MAX_SPIDERS	2
+
+static struct spider_pci_bus {
+	void __iomem	*regs;
+	unsigned long	mmio_start;
+	unsigned long	mmio_end;
+	unsigned long	pio_vstart;
+	unsigned long	pio_vend;
+} spider_pci_busses[MAX_SPIDERS];
+static int spider_pci_count;
+
+static struct spider_pci_bus *spider_pci_find(unsigned long vaddr,
+					      unsigned long paddr)
+{
+	int i;
+
+	for (i = 0; i < spider_pci_count; i++) {
+		struct spider_pci_bus *bus = &spider_pci_busses[i];
+		if (paddr && paddr >= bus->mmio_start && paddr < bus->mmio_end)
+			return bus;
+		if (vaddr && vaddr >= bus->pio_vstart && vaddr < bus->pio_vend)
+			return bus;
+	}
+	return NULL;
+}
+
+static void spider_io_flush(const volatile void __iomem *addr)
+{
+	struct spider_pci_bus *bus;
+	int token;
+
+	/* Get platform token (set by ioremap) from address */
+	token = PCI_GET_ADDR_TOKEN(addr);
+
+	/* Fast path if we have a non-0 token, it indicates which bus we
+	 * are on.
+	 *
+	 * If the token is 0, that means either the the ioremap was done
+	 * before we initialized this layer, or it's a PIO operation. We
+	 * fallback to a low path in this case. Hopefully, internal devices
+	 * which are ioremap'ed early should use in_XX/out_XX functions
+	 * instead of the PCI ones and thus not suffer from the slowdown.
+	 *
+	 * Also note that currently, the workaround will not work for areas
+	 * that are not mapped with PTEs (bolted in the hash table). This
+	 * is the case for ioremaps done very early at boot (before
+	 * mem_init_done) and includes the mapping of the ISA IO space.
+	 *
+	 * Fortunately, none of the affected devices is expected to do DMA
+	 * and thus there should be no problem in practice.
+	 *
+	 * In order to improve performances, we only do the PTE search for
+	 * addresses falling in the PHB IO space area. That means it will
+	 * not work for hotplug'ed PHBs but those don't exist with Spider.
+	 */
+	if (token && token <= spider_pci_count)
+		bus = &spider_pci_busses[token - 1];
+	else {
+		unsigned long vaddr, paddr;
+		pte_t *ptep;
+
+		/* Fixup physical address */
+		vaddr = (unsigned long)PCI_FIX_ADDR(addr);
+
+		/* Check if it's in allowed range for  PIO */
+		if (vaddr < PHBS_IO_BASE || vaddr >= IMALLOC_BASE)
+			return;
+
+		/* Try to find a PTE. If not, clear the paddr, we'll do
+		 * a vaddr only lookup (PIO only)
+		 */
+		ptep = find_linux_pte(init_mm.pgd, vaddr);
+		if (ptep == NULL)
+			paddr = 0;
+		else
+			paddr = pte_pfn(*ptep) << PAGE_SHIFT;
+
+		bus = spider_pci_find(vaddr, paddr);
+		if (bus == NULL)
+			return;
+	}
+
+	/* Now do the workaround
+	 */
+	(void)in_be32(bus->regs + SPIDER_PCI_DUMMY_READ);
+}
+
+static u8 spider_readb(const volatile void __iomem *addr)
+{
+	u8 val = __do_readb(addr);
+	spider_io_flush(addr);
+	return val;
+}
+
+static u16 spider_readw(const volatile void __iomem *addr)
+{
+	u16 val = __do_readw(addr);
+	spider_io_flush(addr);
+	return val;
+}
+
+static u32 spider_readl(const volatile void __iomem *addr)
+{
+	u32 val = __do_readl(addr);
+	spider_io_flush(addr);
+	return val;
+}
+
+static u64 spider_readq(const volatile void __iomem *addr)
+{
+	u64 val = __do_readq(addr);
+	spider_io_flush(addr);
+	return val;
+}
+
+static u16 spider_readw_be(const volatile void __iomem *addr)
+{
+	u16 val = __do_readw_be(addr);
+	spider_io_flush(addr);
+	return val;
+}
+
+static u32 spider_readl_be(const volatile void __iomem *addr)
+{
+	u32 val = __do_readl_be(addr);
+	spider_io_flush(addr);
+	return val;
+}
+
+static u64 spider_readq_be(const volatile void __iomem *addr)
+{
+	u64 val = __do_readq_be(addr);
+	spider_io_flush(addr);
+	return val;
+}
+
+static void spider_readsb(const volatile void __iomem *addr, void *buf,
+			  unsigned long count)
+{
+	__do_readsb(addr, buf, count);
+	spider_io_flush(addr);
+}
+
+static void spider_readsw(const volatile void __iomem *addr, void *buf,
+			  unsigned long count)
+{
+	__do_readsw(addr, buf, count);
+	spider_io_flush(addr);
+}
+
+static void spider_readsl(const volatile void __iomem *addr, void *buf,
+			  unsigned long count)
+{
+	__do_readsl(addr, buf, count);
+	spider_io_flush(addr);
+}
+
+static void spider_memcpy_fromio(void *dest, const volatile void __iomem *src,
+				 unsigned long n)
+{
+	__do_memcpy_fromio(dest, src, n);
+	spider_io_flush(src);
+}
+
+
+static void __iomem * spider_ioremap(unsigned long addr, unsigned long size,
+				     unsigned long flags)
+{
+	struct spider_pci_bus *bus;
+	void __iomem *res = __ioremap(addr, size, flags);
+	int busno;
+
+	pr_debug("spider_ioremap(0x%lx, 0x%lx, 0x%lx) -> 0x%p\n",
+		 addr, size, flags, res);
+
+	bus = spider_pci_find(0, addr);
+	if (bus != NULL) {
+		busno = bus - spider_pci_busses;
+		pr_debug(" found bus %d, setting token\n", busno);
+		PCI_SET_ADDR_TOKEN(res, busno + 1);
+	}
+	pr_debug(" result=0x%p\n", res);
+
+	return res;
+}
+
+static void __init spider_pci_setup_chip(struct spider_pci_bus *bus)
+{
+#ifdef SPIDER_DISABLE_PREFETCH
+	u32 val = in_be32(bus->regs + SPIDER_PCI_VCI_CNTL_STAT);
+	pr_debug(" PVCI_Control_Status was 0x%08x\n", val);
+	out_be32(bus->regs + SPIDER_PCI_VCI_CNTL_STAT, val | 0x8);
+#endif
+
+	/* Configure the dummy address for the workaround */
+	out_be32(bus->regs + SPIDER_PCI_DUMMY_READ_BASE, 0x80000000);
+}
+
+static void __init spider_pci_add_one(struct pci_controller *phb)
+{
+	struct spider_pci_bus *bus = &spider_pci_busses[spider_pci_count];
+	struct device_node *np = phb->arch_data;
+	struct resource rsrc;
+	void __iomem *regs;
+
+	if (spider_pci_count >= MAX_SPIDERS) {
+		printk(KERN_ERR "Too many spider bridges, workarounds"
+		       " disabled for %s\n", np->full_name);
+		return;
+	}
+
+	/* Get the registers for the beast */
+	if (of_address_to_resource(np, 0, &rsrc)) {
+		printk(KERN_ERR "Failed to get registers for spider %s"
+		       " workarounds disabled\n", np->full_name);
+		return;
+	}
+
+	/* Mask out some useless bits in there to get to the base of the
+	 * spider chip
+	 */
+	rsrc.start &= ~0xfffffffful;
+
+	/* Map them */
+	regs = ioremap(rsrc.start + SPIDER_PCI_REG_BASE, 0x1000);
+	if (regs == NULL) {
+		printk(KERN_ERR "Failed to map registers for spider %s"
+		       " workarounds disabled\n", np->full_name);
+		return;
+	}
+
+	spider_pci_count++;
+
+	/* We assume spiders only have one MMIO resource */
+	bus->mmio_start = phb->mem_resources[0].start;
+	bus->mmio_end = phb->mem_resources[0].end + 1;
+
+	bus->pio_vstart = (unsigned long)phb->io_base_virt;
+	bus->pio_vend = bus->pio_vstart + phb->pci_io_size;
+
+	bus->regs = regs;
+
+	printk(KERN_INFO "PCI: Spider MMIO workaround for %s\n",np->full_name);
+
+	pr_debug(" mmio (P) = 0x%016lx..0x%016lx\n",
+		 bus->mmio_start, bus->mmio_end);
+	pr_debug("  pio (V) = 0x%016lx..0x%016lx\n",
+		 bus->pio_vstart, bus->pio_vend);
+	pr_debug(" regs (P) = 0x%016lx (V) = 0x%p\n",
+		 rsrc.start + SPIDER_PCI_REG_BASE, bus->regs);
+
+	spider_pci_setup_chip(bus);
+}
+
+static struct ppc_pci_io __initdata spider_pci_io = {
+	.readb = spider_readb,
+	.readw = spider_readw,
+	.readl = spider_readl,
+	.readq = spider_readq,
+	.readw_be = spider_readw_be,
+	.readl_be = spider_readl_be,
+	.readq_be = spider_readq_be,
+	.readsb = spider_readsb,
+	.readsw = spider_readsw,
+	.readsl = spider_readsl,
+	.memcpy_fromio = spider_memcpy_fromio,
+};
+
+static int __init spider_pci_workaround_init(void)
+{
+	struct pci_controller *phb;
+
+	if (!machine_is(cell))
+		return 0;
+
+	/* Find spider bridges. We assume they have been all probed
+	 * in setup_arch(). If that was to change, we would need to
+	 * update this code to cope with dynamically added busses
+	 */
+	list_for_each_entry(phb, &hose_list, list_node) {
+		struct device_node *np = phb->arch_data;
+		const char *model = get_property(np, "model", NULL);
+
+		/* If no model property or name isn't exactly "pci", skip */
+		if (model == NULL || strcmp(np->name, "pci"))
+			continue;
+		/* If model is not "Spider", skip */
+		if (strcmp(model, "Spider"))
+			continue;
+		spider_pci_add_one(phb);
+	}
+
+	/* No Spider PCI found, exit */
+	if (spider_pci_count == 0)
+		return 0;
+
+	/* Setup IO callbacks. We only setup MMIO reads. PIO reads will
+	 * fallback to MMIO reads (though without a token, thus slower)
+	 */
+	ppc_pci_io = spider_pci_io;
+
+	/* Setup ioremap callback */
+	ppc_md.ioremap = spider_ioremap;
+
+	return 0;
+}
+arch_initcall(spider_pci_workaround_init);