MIPS: PowerTV: Use O(1) algorthm for phys_to_dma/dma_to_phys

Replace phys_to_dma()/dma_to_phys() looping algorithm with an O(1) algorithm
The approach taken is inspired by the sparse memory implementation: take a
certain number of high-order bits off the address them, use this as an
index into a table containing an offset to the desired address and add
it to the original value. There is a table for mapping physical addresses
to DMA addresses and another one for the reverse mapping. The table sizes
depend on how fine-grained the mappings need to be; Coarser granularity
less to smaller tables.  On a processor with 32-bit physical and DMA
addresses, with 4 MIB granularity, memory usage is two 2048-byte arrays.
Each 32-byte cache line thus covers 64 MiB of address space.

Also, renames phys_to_bus() to phys_to_dma() and bus_to_phys() to
dma_to_phys() to align with kernel usage.

[Ralf: Fixed silly build breakage due to stackoverflow warning caused by
huge array on stack.]

Signed-off-by: David VomLehn <dvomlehn@cisco.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1257/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 136 insertions, 0 deletions

diff --git a/arch/mips/powertv/ioremap.c b/arch/mips/powertv/ioremap.c
new file mode 100644
index 000000000000..a77c6f62fe23
--- /dev/null
+++ b/arch/mips/powertv/ioremap.c
@@ -0,0 +1,136 @@
+/*
+ *			ioremap.c
+ *
+ * Support for mapping between dma_addr_t values a phys_addr_t values.
+ *
+ * Copyright (C) 2005-2009 Scientific-Atlanta, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * Author:       David VomLehn <dvomlehn@cisco.com>
+ *
+ * Description:  Defines the platform resources for the SA settop.
+ *
+ * NOTE: The bootloader allocates persistent memory at an address which is
+ * 16 MiB below the end of the highest address in KSEG0. All fixed
+ * address memory reservations must avoid this region.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#include <asm/mach-powertv/ioremap.h>
+
+/*
+ * Define the sizes of and masks for grains in physical and DMA space. The
+ * values are the same but the types are not.
+ */
+#define IOR_PHYS_GRAIN		((phys_addr_t) 1 << IOR_LSBITS)
+#define IOR_PHYS_GRAIN_MASK	(IOR_PHYS_GRAIN - 1)
+
+#define IOR_DMA_GRAIN		((dma_addr_t) 1 << IOR_LSBITS)
+#define IOR_DMA_GRAIN_MASK	(IOR_DMA_GRAIN - 1)
+
+/*
+ * Values that, when accessed by an index derived from a phys_addr_t and
+ * added to phys_addr_t value, yield a DMA address
+ */
+struct ior_phys_to_dma _ior_phys_to_dma[IOR_NUM_PHYS_TO_DMA];
+EXPORT_SYMBOL(_ior_phys_to_dma);
+
+/*
+ * Values that, when accessed by an index derived from a dma_addr_t and
+ * added to that dma_addr_t value, yield a physical address
+ */
+struct ior_dma_to_phys _ior_dma_to_phys[IOR_NUM_DMA_TO_PHYS];
+EXPORT_SYMBOL(_ior_dma_to_phys);
+
+/**
+ * setup_dma_to_phys - set up conversion from DMA to physical addresses
+ * @dma_idx:	Top IOR_LSBITS bits of the DMA address, i.e. an index
+ *		into the array _dma_to_phys.
+ * @delta:	Value that, when added to the DMA address, will yield the
+ *		physical address
+ * @s:		Number of bytes in the section of memory with the given delta
+ *		between DMA and physical addresses.
+ */
+static void setup_dma_to_phys(dma_addr_t dma, phys_addr_t delta, dma_addr_t s)
+{
+	int dma_idx, first_idx, last_idx;
+	phys_addr_t first, last;
+
+	/*
+	 * Calculate the first and last indices, rounding the first up and
+	 * the second down.
+	 */
+	first = dma & ~IOR_DMA_GRAIN_MASK;
+	last = (dma + s - 1) & ~IOR_DMA_GRAIN_MASK;
+	first_idx = first >> IOR_LSBITS;		/* Convert to indices */
+	last_idx = last >> IOR_LSBITS;
+
+	for (dma_idx = first_idx; dma_idx <= last_idx; dma_idx++)
+		_ior_dma_to_phys[dma_idx].offset = delta >> IOR_DMA_SHIFT;
+}
+
+/**
+ * setup_phys_to_dma - set up conversion from DMA to physical addresses
+ * @phys_idx:	Top IOR_LSBITS bits of the DMA address, i.e. an index
+ *		into the array _phys_to_dma.
+ * @delta:	Value that, when added to the DMA address, will yield the
+ *		physical address
+ * @s:		Number of bytes in the section of memory with the given delta
+ *		between DMA and physical addresses.
+ */
+static void setup_phys_to_dma(phys_addr_t phys, dma_addr_t delta, phys_addr_t s)
+{
+	int phys_idx, first_idx, last_idx;
+	phys_addr_t first, last;
+
+	/*
+	 * Calculate the first and last indices, rounding the first up and
+	 * the second down.
+	 */
+	first = phys & ~IOR_PHYS_GRAIN_MASK;
+	last = (phys + s - 1) & ~IOR_PHYS_GRAIN_MASK;
+	first_idx = first >> IOR_LSBITS;		/* Convert to indices */
+	last_idx = last >> IOR_LSBITS;
+
+	for (phys_idx = first_idx; phys_idx <= last_idx; phys_idx++)
+		_ior_phys_to_dma[phys_idx].offset = delta >> IOR_PHYS_SHIFT;
+}
+
+/**
+ * ioremap_add_map - add to the physical and DMA address conversion arrays
+ * @phys:	Process's view of the address of the start of the memory chunk
+ * @dma:	DMA address of the start of the memory chunk
+ * @size:	Size, in bytes, of the chunk of memory
+ *
+ * NOTE: It might be obvious, but the assumption is that all @size bytes have
+ * the same offset between the physical address and the DMA address.
+ */
+void ioremap_add_map(phys_addr_t phys, phys_addr_t dma, phys_addr_t size)
+{
+	if (size == 0)
+		return;
+
+	if ((dma & IOR_DMA_GRAIN_MASK) != 0 ||
+		(phys & IOR_PHYS_GRAIN_MASK) != 0 ||
+		(size & IOR_PHYS_GRAIN_MASK) != 0)
+		pr_crit("Memory allocation must be in chunks of 0x%x bytes\n",
+			IOR_PHYS_GRAIN);
+
+	setup_dma_to_phys(dma, phys - dma, size);
+	setup_phys_to_dma(phys, dma - phys, size);
+}