[PATCH 2/3] Revert "bus: mvebu-mbus: make sure SDRAM CS for DMA don't overlap the MBus bridge window"
Thomas Petazzoni
thomas.petazzoni at free-electrons.com
Thu May 28 01:40:13 PDT 2015
This reverts commit 1737cac69369 ("bus: mvebu-mbus: make sure SDRAM CS
for DMA don't overlap the MBus bridge window"), because it breaks DMA
on platforms having more than 2 GB of RAM.
This commit changed the information reported to DMA masters device
drivers through the mv_mbus_dram_info() function so that the returned
DRAM ranges do not overlap with I/O windows.
This was necessary as a preparation to support the new CESA Crypto
Engine driver, which will use DMA for cryptographic operations. But
since it does DMA with the SRAM which is mapped as an I/O window,
having DRAM ranges overlapping with I/O windows was problematic.
To solve this, the above mentioned commit changed the mvebu-mbus to
adjust the DRAM ranges so that they don't overlap with the I/O
windows. However, by doing this, we re-adjust the DRAM ranges in a way
that makes them have a size that is no longer a power of two. While
this is perfectly fine for the Crypto Engine, which supports DRAM
ranges with a granularity of 64 KB, it breaks basically all other DMA
masters, which expect power of two sizes for the DRAM ranges.
Due to this, if the installed system memory is 4 GB, in two
chip-selects of 2 GB, the second DRAM range will be reduced from 2 GB
to a little bit less than 2 GB to not overlap with the I/O windows, in
a way that results in a DRAM range that doesn't have a power of two
size. This means that whenever you do a DMA transfer with an address
located in the [ 2 GB ; 4 GB ] area, it will freeze the system. Any
serious DMA activity like simply running:
for i in $(seq 1 64) ; do dd if=/dev/urandom of=file$i bs=1M count=16 ; done
in an ext3 partition mounted over a SATA drive will freeze the system.
Since the new CESA crypto driver that uses DMA has not been merged
yet, the easiest fix is to simply revert this commit. A follow-up
commit will introduce a different solution for the CESA crypto driver.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Fixes: 1737cac69369 ("bus: mvebu-mbus: make sure SDRAM CS for DMA don't overlap the MBus bridge window")
Cc: <stable at vger.kernel.org> # v4.0+
---
drivers/bus/mvebu-mbus.c | 105 ++++++++---------------------------------------
1 file changed, 16 insertions(+), 89 deletions(-)
diff --git a/drivers/bus/mvebu-mbus.c b/drivers/bus/mvebu-mbus.c
index 7fa4510..6f047dc 100644
--- a/drivers/bus/mvebu-mbus.c
+++ b/drivers/bus/mvebu-mbus.c
@@ -58,7 +58,6 @@
#include <linux/debugfs.h>
#include <linux/log2.h>
#include <linux/syscore_ops.h>
-#include <linux/memblock.h>
/*
* DDR target is the same on all platforms.
@@ -103,9 +102,7 @@
/* Relative to mbusbridge_base */
#define MBUS_BRIDGE_CTRL_OFF 0x0
-#define MBUS_BRIDGE_SIZE_MASK 0xffff0000
#define MBUS_BRIDGE_BASE_OFF 0x4
-#define MBUS_BRIDGE_BASE_MASK 0xffff0000
/* Maximum number of windows, for all known platforms */
#define MBUS_WINS_MAX 20
@@ -579,106 +576,36 @@ static unsigned int armada_xp_mbus_win_remap_offset(int win)
return MVEBU_MBUS_NO_REMAP;
}
-/*
- * Use the memblock information to find the MBus bridge hole in the
- * physical address space.
- */
-static void __init
-mvebu_mbus_find_bridge_hole(uint64_t *start, uint64_t *end)
-{
- struct memblock_region *r;
- uint64_t s = 0;
-
- for_each_memblock(memory, r) {
- /*
- * This part of the memory is above 4 GB, so we don't
- * care for the MBus bridge hole.
- */
- if (r->base >= 0x100000000)
- continue;
-
- /*
- * The MBus bridge hole is at the end of the RAM under
- * the 4 GB limit.
- */
- if (r->base + r->size > s)
- s = r->base + r->size;
- }
-
- *start = s;
- *end = 0x100000000;
-}
-
static void __init
mvebu_mbus_default_setup_cpu_target(struct mvebu_mbus_state *mbus)
{
int i;
int cs;
- uint64_t mbus_bridge_base, mbus_bridge_end;
mvebu_mbus_dram_info.mbus_dram_target_id = TARGET_DDR;
- mvebu_mbus_find_bridge_hole(&mbus_bridge_base, &mbus_bridge_end);
-
for (i = 0, cs = 0; i < 4; i++) {
- u64 base = readl(mbus->sdramwins_base + DDR_BASE_CS_OFF(i));
- u64 size = readl(mbus->sdramwins_base + DDR_SIZE_CS_OFF(i));
- u64 end;
- struct mbus_dram_window *w;
-
- /* Ignore entries that are not enabled */
- if (!(size & DDR_SIZE_ENABLED))
- continue;
-
- /*
- * Ignore entries whose base address is above 2^32,
- * since devices cannot DMA to such high addresses
- */
- if (base & DDR_BASE_CS_HIGH_MASK)
- continue;
-
- base = base & DDR_BASE_CS_LOW_MASK;
- size = (size | ~DDR_SIZE_MASK) + 1;
- end = base + size;
-
- /*
- * Adjust base/size of the current CS to make sure it
- * doesn't overlap with the MBus bridge hole. This is
- * particularly important for devices that do DMA from
- * DRAM to a SRAM mapped in a MBus window, such as the
- * CESA cryptographic engine.
- */
+ u32 base = readl(mbus->sdramwins_base + DDR_BASE_CS_OFF(i));
+ u32 size = readl(mbus->sdramwins_base + DDR_SIZE_CS_OFF(i));
/*
- * The CS is fully enclosed inside the MBus bridge
- * area, so ignore it.
+ * We only take care of entries for which the chip
+ * select is enabled, and that don't have high base
+ * address bits set (devices can only access the first
+ * 32 bits of the memory).
*/
- if (base >= mbus_bridge_base && end <= mbus_bridge_end)
- continue;
+ if ((size & DDR_SIZE_ENABLED) &&
+ !(base & DDR_BASE_CS_HIGH_MASK)) {
+ struct mbus_dram_window *w;
- /*
- * Beginning of CS overlaps with end of MBus, raise CS
- * base address, and shrink its size.
- */
- if (base >= mbus_bridge_base && end > mbus_bridge_end) {
- size -= mbus_bridge_end - base;
- base = mbus_bridge_end;
+ w = &mvebu_mbus_dram_info.cs[cs++];
+ w->cs_index = i;
+ w->mbus_attr = 0xf & ~(1 << i);
+ if (mbus->hw_io_coherency)
+ w->mbus_attr |= ATTR_HW_COHERENCY;
+ w->base = base & DDR_BASE_CS_LOW_MASK;
+ w->size = (size | ~DDR_SIZE_MASK) + 1;
}
-
- /*
- * End of CS overlaps with beginning of MBus, shrink
- * CS size.
- */
- if (base < mbus_bridge_base && end > mbus_bridge_base)
- size -= end - mbus_bridge_base;
-
- w = &mvebu_mbus_dram_info.cs[cs++];
- w->cs_index = i;
- w->mbus_attr = 0xf & ~(1 << i);
- if (mbus->hw_io_coherency)
- w->mbus_attr |= ATTR_HW_COHERENCY;
- w->base = base;
- w->size = size;
}
mvebu_mbus_dram_info.num_cs = cs;
}
--
2.1.0
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