From: mikko.perttunen@kapsi•fi (Mikko Perttunen)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH 1/4] memory: tegra124-emc: Add EMC driver
Date: Tue, 17 Jun 2014 19:59:35 +0300 [thread overview]
Message-ID: <53A073F7.20700@kapsi.fi> (raw)
In-Reply-To: <53A069B6.6070902@wwwdotorg.org>
On 06/17/2014 07:15 PM, Stephen Warren wrote:
> On 06/17/2014 06:16 AM, Tomeu Vizoso wrote:
>> On 06/16/2014 10:02 PM, Stephen Warren wrote:
>>> On 06/16/2014 07:35 AM, Tomeu Vizoso wrote:
>
>>> This binding looks quite anaemic vs.
>>> Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-emc.txt; I
>>> would expect that this binding needs all the EMC register data from the
>>> tegra20-emc binding too. Can the two bindings be identical?
>>
>> There's even less stuff needed right now, as all what ultimately the EMC
>> driver does is call clk_set_rate on the EMC clock. As the T124 EMC
>> driver gains more features, they should get more similar.
>
> IIRC, even changing the EMC clock rate requires modifying the memory
> controller's programming (e.g. delays/taps/tuning etc.). That's exactly
> what the more complex stuff in the nvidia,tegra20-emc.txt is all about.
> I not convinced that a driver that just modifies the clock rate without
> adjusting the EMC programming will work reliably.
Indeed, changing the EMC clock rate is a somewhat complicated sequence
of ~10 steps. The kernel even won't let one the rate be change directly,
as the change would be propagated to PLL_M which cannot have its rate
changed while it is enabled. I suppose the sequence should be hidden in
the EMC clk's set_rate implementation, which I guess would leave just
the rate policy to this driver.
next prev parent reply other threads:[~2014-06-17 16:59 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-16 13:35 [RFC PATCH 0/4] Tegra124: EMC scaling Tomeu Vizoso
2014-06-16 13:35 ` [RFC PATCH 1/4] memory: tegra124-emc: Add EMC driver Tomeu Vizoso
2014-06-16 14:03 ` Mikko Perttunen
2014-06-16 20:02 ` Stephen Warren
2014-06-17 12:16 ` Tomeu Vizoso
2014-06-17 16:15 ` Stephen Warren
2014-06-17 16:59 ` Mikko Perttunen [this message]
2014-06-18 17:23 ` Tomeu Vizoso
2014-06-18 17:46 ` Stephen Warren
2014-06-18 22:03 ` Thierry Reding
2014-06-18 22:09 ` Stephen Warren
2014-06-18 23:14 ` Thierry Reding
2014-06-18 23:24 ` Stephen Warren
2014-06-18 22:00 ` Thierry Reding
2014-06-18 22:19 ` Stéphane Marchesin
2014-06-18 22:33 ` Stephen Warren
2014-06-18 23:20 ` Thierry Reding
2014-06-17 22:35 ` Thierry Reding
2014-06-18 8:57 ` Peter De Schrijver
2014-06-16 13:35 ` [RFC PATCH 2/4] ARM: tegra: Add Tegra124 EMC support Tomeu Vizoso
2014-06-17 22:38 ` Thierry Reding
2014-06-16 13:35 ` [RFC PATCH 3/4] drm/tegra: Request memory bandwidth for the display controller Tomeu Vizoso
2014-06-16 20:06 ` Stephen Warren
2014-06-17 22:43 ` Thierry Reding
2014-06-16 13:35 ` [RFC PATCH 4/4] cpufreq: tegra: Register a minimum EMC frequency based on the CPU clock Tomeu Vizoso
2014-06-16 14:08 ` Mikko Perttunen
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