On 2/25/22 10:18, Pratyush Yadav wrote:
On 14/02/22 10:42AM, Cédric Le Goater wrote:
To accommodate the different response time of SPI transfers on different
boards and different SPI NOR devices, the Aspeed controllers provide a
set of Read Timing Compensation registers to tune the timing delays
depending on the frequency being used. The AST2600 SoC has one of
these registers per device. On the AST2500 and AST2400 SoCs, the
timing register is shared by all devices which is a bit problematic to
get good results other than for one device.
The algorithm first reads a golden buffer at low speed and then performs
reads with different clocks and delay cycle settings to find a breaking
point. This selects a default good frequency for the CEx control register.
The current settings are bit optimistic as we pick the first delay giving
good results. A safer approach would be to determine an interval and
choose the middle value.
Due to the lack of API, calibration is performed when the direct mapping
for reads is created.
The dirmap_create mapping says nothing about _when_ it should be called.
So there is no guarantee that it will only be called after the flash is
fully initialized.
spi_nor_create_read_dirmap() is called after spi_nor_scan() in spi_nor_probe().
Since a spi_mem_dirmap_info descriptor is created using the nor fields :
struct spi_mem_dirmap_info info = {
.op_tmpl = SPI_MEM_OP(SPI_MEM_OP_CMD(nor->read_opcode, 0),
SPI_MEM_OP_ADDR(nor->addr_width, 0, 0),
SPI_MEM_OP_DUMMY(nor->read_dummy, 0),
SPI_MEM_OP_DATA_IN(0, NULL, 0)),
.offset = 0,
.length = nor->params->size,
};
struct spi_mem_op *op = &info.op_tmpl;
the spi-mem framework makes the assumption that the nor object is initialized.
I suggest you either make this a requirement of the API,
how ?
Thanks,
C.
or create a new API that guarantees it will only be called after
the flash is initialized, like [0].
[0] https://patchwork.ozlabs.org/project/linux-mtd/patch/20210311191216.7363-2-p.yadav@xxxxxx/
Cc: Pratyush Yadav <p.yadav@xxxxxx>
Signed-off-by: Cédric Le Goater <clg@xxxxxxxx>
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