Lately we have working on Flash interface unit (FIU) SPI driver that
using spi-mem interface, Our FIU HW module support direct Flash Rd//Wr.
In our SOC (32 bit dual core ARM) we have 3 FIU's that using memory mapping as
follow:
FIU0 - have 2 chip select and each one have 128MB memory mapping (total 256MB
memory mapping)
FIU1 - have 4 chip select and each one have 128MB memory mapping (total 512MB
memory mapping)
FIU2 - have 4 chip select and each one have 16MB memory mapping (total 32MB
memory mapping)
Totally 800MB memory mapping.
When the FIU driver probe it don't know the size of each Flash that
connected to the FIU, so the entire memory mapping is allocated for each FIU
according the FIU device tree memory map parameters.
It means, if we enable all three FIU's the drivers will try to allocate totally
800MB.
In 32bit system it is problematic because the kernel have only 1GB
of memory allocation so the vmalloc cannot take 800MB.
When implementing the FIU driver in the mtd/spi-nor we allocating memory
address only
for detected Flash with exact size (usually we are not using 128MB Flash), and
in that case usually we allocating much less memory.
To solve this issue we needed to overcome two things:
1. Get argument from the upper layer (spi-mem layer)
2. Calling the get argument function after SPI_NOR_SCAN function. (the MTD
Flash size filled in SPI_NOR_SCAN function)
The attach patch set solving the describe issue by:
1. Add spi-mem callback function and value to the SPI device
for passing an argument from the spi-mem layer to the spi layer
2. Add spi-mem setup function to the spi-memory operation that running
after the spi-mem probe finished.
3. Implement function callback in the m25p80 driver that execute
get Flash size.
The patch set tested on NPCM750 EVB with FIU driver (implemented with SPI-MEM
interface).
Thanks for your attention.
Tomer
Tomer Maimon (3):
spi: spi-mem: add spi-mem setup function
spi: spi-mem: add callback function to spi-mem device
mtd: m25p80: add get Flash size callback support
drivers/mtd/devices/m25p80.c | 12 ++++++++++++
drivers/spi/spi-mem.c | 27 ++++++++++++++++++++++++++-
include/linux/spi/spi-mem.h | 11 +++++++++++
3 files changed, 49 insertions(+), 1 deletion(-)
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2.18.0
