[PATCH v7 0/4] Add generic driver for on-chip SRAM

[Philipp Zabel]

These patches add support to configure on-chip SRAM via device-tree
node or platform data and to obtain the resulting genalloc pool from
the physical address or a phandle pointing at the device tree node.
This allows drivers to allocate SRAM with the genalloc API without
hard-coding the genalloc pool pointer.

The on-chip SRAM on i.MX53 and i.MX6q can be registered via device tree
and changed to use the simple generic SRAM driver:

                ocram: ocram at 00900000 {
                        compatible = "fsl,imx-ocram", "sram";
                        reg = <0x00900000 0x3f000>;
                };

A driver that needs to allocate SRAM buffers, like the video processing
unit on i.MX53, can retrieve the genalloc pool from a phandle in the
device tree using of_get_named_gen_pool(node, "iram", 0) from patch 1:

                vpu at 63ff4000 {
                        /* ... */
                        iram = <&ocram>;
                };

The allocation granularity is hard-coded to 32 bytes for now,
until a way to configure it can be agreed upon. There is overhead
for bigger SRAMs, where only a much coarser allocation granularity
is needed: At 32 bytes minimum allocation size, a 256 KiB SRAM
needs a 1 KiB bitmap to track allocations.

Once everybody is ok with it, could the first two patches be merged
through the char-misc tree? I'll resend the i.MX and coda patches to
the respective lists afterwards.

Changes since v6:
 - Reduced the hard coded allocation granularity to 32 bytes.

regards
Philipp

---
 Documentation/devicetree/bindings/misc/sram.txt |   17 ++++
 arch/arm/boot/dts/imx53.dtsi                    |    5 +
 arch/arm/boot/dts/imx6q.dtsi                    |    6 ++
 drivers/media/platform/Kconfig                  |    3 +-
 drivers/media/platform/coda.c                   |   47 ++++++---
 drivers/misc/Kconfig                            |    9 ++
 drivers/misc/Makefile                           |    1 +
 drivers/misc/sram.c                             |  121 +++++++++++++++++++++++
 include/linux/genalloc.h                        |   14 +++
 lib/genalloc.c                                  |   67 +++++++++++++
 10 files changed, 274 insertions(+), 16 deletions(-)