[PATCH v4 1/4] ARM: OMAP2+: AM33XX: I2C Sleep/wake sequence support

[Russ Dill]

On Sun, Aug 18, 2013 at 10:49 PM, Gururaja Hebbar
<gururaja.hebbar at ti.com> wrote:
>
> On 8/15/2013 4:04 AM, Russ Dill wrote:
> > On Wed, Aug 14, 2013 at 3:18 AM, Gururaja Hebbar <gururaja.hebbar at ti.com> wrote:
> >> On 8/14/2013 3:50 AM, Russ Dill wrote:
> >>> Changes since v1:
> >>> * Rebased onto new am335x PM branch
> >>> * Changed to use 5th param register
>
> >>
>
> [snip]
> [snip]
>
> >>> +
> >>> +     wkup_m3_reset_data_pos();
> >>> +     if (am33xx_i2c_sleep_sequence) {
> >>> +             pos = wkup_m3_copy_data(am33xx_i2c_sleep_sequence,
> >>> +                                             i2c_sleep_sequence_sz);
> >>
> >> Why do we need to copy this data (same constant data) on every iteration?
> >
> > Because the CM3 firmware is reset after each suspend/resume cycle. The
> > firmware reset handler reinitializes the DMEM.
>
> Well in that why can't the i2c payload be copied to UMEM?
>
> Thanks & regards
> Gururaja
>

I've given this some thought, and gone back and forth a bit. UMEM is a
bit more complicated because the linker decides what should go where.
Also, it may be that in the future, either the PM for am335x or am43xx
will be writing different sequences depending on the suspend
mode/options.

Is there a specific aspect of copying the data each suspend cycle that
you are trying to fix? Is it just that the data could only be copied
once? Or is it the latency of the copy?

Thanks!