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.