From: mperttunen@nvidia•com (Mikko Perttunen)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 5/8] of: Add Tegra124 EMC bindings
Date: Mon, 14 Jul 2014 13:54:36 +0300 [thread overview]
Message-ID: <53C3B6EC.9090904@nvidia.com> (raw)
In-Reply-To: <20140714102954.GD9870@ulmo>
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
>
next prev parent reply other threads:[~2014-07-14 10:54 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-11 14:18 [PATCH 0/8] Tegra124 EMC (external memory controller) support Mikko Perttunen
2014-07-11 14:18 ` [PATCH 1/8] clk: tegra124: Remove old emc_mux and emc clocks Mikko Perttunen
2014-07-11 14:18 ` [PATCH 2/8] ARM: tegra: Remove TEGRA124_CLK_EMC from tegra124-car.h Mikko Perttunen
2014-07-21 22:37 ` Stephen Warren
2014-07-29 8:28 ` Mikko Perttunen
2014-07-11 14:18 ` [PATCH 3/8] ARM: tegra: Add PLL_M_UD and PLL_C_UD to tegra124-car binding header Mikko Perttunen
2014-08-25 17:41 ` Stephen Warren
2014-09-17 13:41 ` Peter De Schrijver
2014-07-11 14:18 ` [PATCH 4/8] clk: tegra124: Add PLL_M_UD and PLL_C_UD clocks Mikko Perttunen
2014-07-11 14:18 ` [PATCH 5/8] of: Add Tegra124 EMC bindings Mikko Perttunen
2014-07-11 14:51 ` Thierry Reding
2014-07-11 16:01 ` Mikko Perttunen
2014-07-14 7:55 ` Mikko Perttunen
2014-07-14 8:15 ` Thierry Reding
2014-07-14 9:06 ` Mikko Perttunen
2014-07-14 9:31 ` Thierry Reding
2014-07-14 9:57 ` Mikko Perttunen
2014-07-14 10:29 ` Thierry Reding
2014-07-14 10:54 ` Mikko Perttunen [this message]
2014-07-14 11:10 ` Thierry Reding
2014-07-14 12:28 ` Mikko Perttunen
2014-07-11 16:43 ` Andrew Bresticker
2014-07-11 16:48 ` Mikko Perttunen
2014-07-21 21:28 ` Stephen Warren
2014-07-21 22:52 ` Andrew Bresticker
2014-07-22 16:45 ` Stephen Warren
2014-07-22 17:22 ` Andrew Bresticker
2014-07-22 17:34 ` Stephen Warren
2014-07-29 8:30 ` Mikko Perttunen
2014-07-29 15:49 ` Stephen Warren
2014-07-31 10:48 ` Mikko Perttunen
2014-07-31 11:05 ` Mikko Perttunen
2014-07-31 15:32 ` Stephen Warren
2014-07-21 22:36 ` Stephen Warren
2014-07-11 14:18 ` [PATCH 6/8] ARM: tegra: Add EMC to Tegra124 device tree Mikko Perttunen
2014-07-11 14:18 ` [PATCH 7/8] ARM: tegra: Add EMC timings to Jetson TK1 " Mikko Perttunen
2014-07-11 14:18 ` [PATCH 8/8] clk: tegra: Add EMC clock driver Mikko Perttunen
2014-07-22 16:57 ` Stephen Warren
2014-07-29 8:47 ` Mikko Perttunen
2014-07-29 20:19 ` Mike Turquette
2014-07-29 22:14 ` Stephen Warren
2014-07-30 9:34 ` Thierry Reding
2014-07-31 19:06 ` Mike Turquette
2014-07-31 19:53 ` Stephen Warren
2014-07-31 23:08 ` Mike Turquette
2014-08-01 6:31 ` Mikko Perttunen
2014-08-01 8:40 ` Thierry Reding
2014-08-25 17:40 ` [PATCH 0/8] Tegra124 EMC (external memory controller) support Stephen Warren
2014-08-26 7:42 ` Mikko Perttunen
2014-08-26 7:47 ` Thierry Reding
2014-08-26 8:02 ` Mikko Perttunen
2014-09-05 10:22 ` Tomeu Vizoso
2014-09-05 10:55 ` Mikko Perttunen
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