Hei hei,
With
#define ATMEL_SMC_MODE_TDF(x) (((x) - 1) << 16)
from include/linux/mfd/syscon/atmel-smc.h you added this:
> + ret = of_property_read_u32(np, "atmel,smc-tdf-ns", &val);
> + if (!ret) {
> + required = true;
> + ncycles = DIV_ROUND_UP(val, clk_period_ns);
> + if (ncycles > ATMEL_SMC_MODE_TDF_MAX) {
> + ret = -EINVAL;
> + goto out;
> + }
[…]
> + smcconf->mode |= ATMEL_SMC_MODE_TDF(ncycles);
> + }
This was the same algorithm at some other location in atmel-ebi.c
before:
#define AT91_SMC_TDF_(x) ((((x) - 1) << 16) &
AT91_SMC_TDF)
val = DIV_ROUND_UP(timings->tdf_ns, clk_rate);
if (val > AT91_SMC_TDF_MAX)
val = AT91_SMC_TDF_MAX;
regmap_fields_write(fields->mode, conf->cs,
config->mode | AT91_SMC_TDF_(val));
The hardware manual (AT91SAM9G20) says values from 0 to 15 (4bit, 0x0 to
0xF) are possible and I guess the goal is to set it to a value
corresponding to the value in ns from the dts or to 15 if it's greater
(or -EINVAL in the new version).
However how can one set it to zero? Put in zero to the div you get zero
for ncycles or val and that goes as x into (((x) - 1) << 16) which
results in 0xF ending up as TDF_CYCLES in the mode register, right?
I can of course set a slightly greater value, which ends up in a
calculated register value of zero, but that seems more a hack to me and
is not obvious if I just look at the DTS.
If I'm right this might be topic of another bugfix patch, or should it
be done right in a v2 of this one?
Greets
Alex
