Hi,
the i2c-mxs driver does not work when transmit buffers are located
within module memory.
E.g. when doing something like
struct i2c_msg xfer = {
.buf = "something",
...
};
ret = i2c_transfer(client->adapter, &xfer, 1);
random data will be sent because buf is not DMA mapable ("something" is
located in the .strtab section within module memory). MXS has a memory
layout like
vmalloc : 0xc8800000 - 0xff000000 ( 872 MB)
lowmem : 0xc0000000 - 0xc8000000 ( 128 MB)
modules : 0xbf000000 - 0xc0000000 ( 16 MB)
.text : 0xc0008000 - 0xc04b1e8c (4776 kB)
.init : 0xc04b2000 - 0xc04e61ac ( 209 kB)
.data : 0xc04e8000 - 0xc051b578 ( 206 kB)
.bss : 0xc051b578 - 0xc05eba44 ( 834 kB)
and is CONFIG_FLATMEM. Buffers above are e.g. at 0xbf0cdaf0.
You can verify the problem e.g. with the edt-ft5x06.c touch driver;
dumping 'sg->dma_address' in mxs_dma_prep_slave_sg() shows physical
addresses like 0x3f0cdaf0 for such strings, which are outside of valid
memory (0x40000000-0x7fffffff).
Does the i2c layer require DMA mapable buffers in its xfer structures
(e.g. like usb), or is the problem in the generic ARM/MXS layer or in
the mxs i2c driver?
Enrico
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