On 14/07/14 13:29, Thierry Reding wrote:
* PGP Signed by an unknown key
> ...
Yes, this sounds sensible. I'll make such a patch. I suppose having another
timings table in the MC node with just the rate and mc-burst-data would
separate the concerns best. It occurs to me that we could also write the
regs in the pre-rate change notifier, but this would turn the dependency
around and would mean that the regs are not written when entering backup
rates. The latter shouldn't be a problem but the reversed dependency would,
so I guess a custom function is the way to go, and we need to add at least
one anyway.
It sounds like maybe moving enough code and data into the MC driver to
handle frequency changes would be a good move. From the above it sounds
like all the MC driver needs to know is that a frequency change is about
to happen and what the new frequency is.
In addition to exposing things like number of DRAM banks, etc.
Yes, so there are two ways to do this:
1) EMC calls tegra_mc_emem_update(freq) at the correct time
2) MC has an optional clock phandle to the EMC clock and registers a
pre-change notifier.
Both work, but the dependency is reversed. In both cases, the other
driver is also optional. In the first case, the EMC driver can give a
warning if the call fails. (As mentioned, if the MC_EMEM updates don't
happen, things still work but potentially with a hefty perf loss.)
TBH, I haven't yet decided which one is better. If you have an opinion,
I'll go with it.
The downstream kernel also overwrites most LA registers during EMC rate
change without regard for the driver-set values, and we might have to read
those values from the device tree too. Upstream can do this in rate change
notifiers if needed. I'll look into this a bit more.
As I understand it, the latency allowance should be specified in terms
of the maximum amount of time that requests are delayed, so that the
proper values for the LA registers can be recomputed on an EMC rate
change.
That's how I understand it too, but in downstream, the LA register
values are hardcoded into EMC tables in platform data/DTS that are just
written into the LA registers as-is during rate change.
Thierry
* Unknown Key
* 0x7F3EB3A1
--
To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
