bus: mvebu-mbus: add mv_mbus_dram_info_nooverlap()

This commit introduces a variant of the mv_mbus_dram_info() function
called mv_mbus_dram_info_nooverlap(). Both functions are used by
Marvell drivers supporting devices doing DMA, and provide them a
description the DRAM ranges that they need to configure their DRAM
windows.

The ranges provided by the mv_mbus_dram_info() function may overlap
with the I/O windows if there is a lot (>= 4 GB) of RAM
installed. This is not a problem for most of the DMA masters, except
for the upcoming new CESA crypto driver because it does DMA to the
SRAM, which is mapped through an I/O window. For this unit, we need to
have DRAM ranges that do not overlap with the I/O windows.

A first implementation done in commit 1737cac69369 ("bus: mvebu-mbus:
make sure SDRAM CS for DMA don't overlap the MBus bridge window"),
changed the information returned by mv_mbus_dram_info() to match this
requirement. However, it broke the requirement of the other DMA
masters than the DRAM ranges should have power of two sizes.

To solve this situation, this commit introduces a new
mv_mbus_dram_info_nooverlap() function, which returns the same
information as mv_mbus_dram_info(), but guaranteed to not overlap with
the I/O windows.

In the end, it gives us two variants of the mv_mbus_dram_info*()
functions:

 - The normal one, mv_mbus_dram_info(), which has been around for many
   years. This function returns the raw DRAM ranges, which are
   guaranteed to use power of two sizes, but will overlap with I/O
   windows. This function will therefore be used by all DMA masters
   (SATA, XOR, Ethernet, etc.) except the CESA crypto driver.

 - The new 'nooverlap' variant, mv_mbus_dram_info_nooverlap(). This
   function returns DRAM ranges after they have been "tweaked" to make
   sure they don't overlap with I/O windows. By doing this tweaking,
   we remove the power of two size guarantee. This variant will be
   used by the new CESA crypto driver.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/mbus.h b/include/linux/mbus.h
index 611b69fa8594..1f7bc630d225 100644
--- a/include/linux/mbus.h
+++ b/include/linux/mbus.h
@@ -54,11 +54,16 @@ struct mbus_dram_target_info
  */
 #ifdef CONFIG_PLAT_ORION
 extern const struct mbus_dram_target_info *mv_mbus_dram_info(void);
+extern const struct mbus_dram_target_info *mv_mbus_dram_info_nooverlap(void);
 #else
 static inline const struct mbus_dram_target_info *mv_mbus_dram_info(void)
 {
 	return NULL;
 }
+static inline const struct mbus_dram_target_info *mv_mbus_dram_info_nooverlap(void)
+{
+	return NULL;
+}
 #endif
 
 int mvebu_mbus_save_cpu_target(u32 *store_addr);