[PATCH 6/7] ARM: dts: sun6i: Add required ahb1 clock parent and rates for dma controller

On Fri, Sep 12, 2014 at 10:10:25AM +0800, Chen-Yu Tsai wrote:

On Fri, Sep 12, 2014 at 5:15 AM, Maxime Ripard
[off-list ref] wrote:

quoted

On Sat, Sep 06, 2014 at 06:47:27PM +0800, Chen-Yu Tsai wrote:

quoted

The DMA controller requires AHB1 bus clock to be clocked from PLL6.

Signed-off-by: Chen-Yu Tsai <redacted>
---
 arch/arm/boot/dts/sun6i-a31.dtsi | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm/boot/dts/sun6i-a31.dtsi b/arch/arm/boot/dts/sun6i-a31.dtsi
index 8eb2c6d..1117989 100644
--- a/arch/arm/boot/dts/sun6i-a31.dtsi
+++ b/arch/arm/boot/dts/sun6i-a31.dtsi

@@ -317,6 +317,11 @@
                      clocks = <&ahb1_gates 6>;
                      resets = <&ahb1_rst 6>;
                      #dma-cells = <1>;
+
+                     /* DMA controller requires AHB1 clocked from PLL6 */
+                     assigned-clocks = <&ahb1>;
+                     assigned-clock-parents = <&pll6>;
+                     assigned-clock-rates = <200000000>;

Where did you get that from?

The user manual says that it should be clocked at 600MHz, and I'm not
sure it should be enforced there either.

The bindings mean that ahb1 should be clocked from pll6 and at 200 MHz,
not "pll6 should be 200 MHz". I assume you were misled by them.

Clocking ahb1 from pll6 and at 200 MHz with the /3 pre-divider is the
vendor BSP default:

On sun6i, the clock init code calls aw_ccu_switch_ahb_2_pll6(), which muxes
ahb1 from pll6 with the highest dividers, then sets the rate for ahb1 to
pll6, which sets pre-divider to /3 and divider to /1.

Hope this clears it up. :)

It does, thanks :)

But still, I find it the wrong place to enforce such a limit. This
should go into the clock driver itself. The DMA controller requires
such a parenting, but it doesn't require any specific rate, this is
more something of the global system policy.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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