On 13/05/15 12:45, Maxime Coquelin wrote:
2015-05-12 23:21 GMT+02:00 Arnd Bergmann <arnd@xxxxxxxx>:
On Saturday 09 May 2015 09:53:56 Maxime Coquelin wrote:
+#include <dt-bindings/mfd/stm32f4-rcc.h>
+
Can you find a way to avoid this dependency?
Maybe you can change the bindings so that the numbers you pass as
arguments to the reset and clock specifiers reflect the numbers that
the hardware use?
If I understand correctly, you prefer the way I did in v7 [0]?
I don't have a strong opinion on this. Either way is fine to me.
I changed the bindings in the v8 after discussions with Daniel
Thompson, who is implementing the clock driver part of the RCC IP.
He proposed we used common defines, because each peripheral has a
reset line and a clock gate.
Both reset and clock are represented as a single bit, with only the
base offset differing between clock and reset.
You can have a look at chapter 6 of the reference manual [1] if you
find some time.
Having common defines between clocks and reset make sense to me, but I
also understand your point of avoiding dependencies.
Maybe I can revert back to v7 bindings for now, and then we can
reconsider using common defines when Daniel will send the clock
patches.
Note that doing that won't break the DT binary compatibility, as the
raw reset values, or the ones from defines are the same.
Daniel, could you share an example of the bindings you would use for the clocks?
For the most cases, where there is a clock gate just before the
peripheral it looks pretty much like the reset driver and I use the bit
offset of the clock gating bit as the index.
However there are a couple of clocks without gating just before the
clock reaches the peripheral:
1. A hard coded /8. I think this will have to be given a synthetic
number.
2. Ungated dividers. For these I am using the bit offset of the LSB of
the mux field.
So I think there is only one value that is completely unrelated to the
hardware and will use a magic constant instead.
I had planned to macros similar to the STM32F4_AxB_RESET() family of
macros in both clk driver and DT in order to reuse the bit layouts from
dt-bindings/mfd/stm32f4-rcc.h .
Normal case would have looked like this:
timer3: timer@40000000 {
compatible = "st,stm32-timer";
reg = <0x40000000 0x400>;
interrupts = <28>;
resets = <&rcc STM32F4_APB1_RESET(TIM3)>;
clocks = <&rcc STM32F4_APB1_CLK(TIM3)>;
status = "disabled";
};
Without the macros it looks like this:
timer3: timer@40000000 {
compatible = "st,stm32-timer";
reg = <0x40000000 0x400>;
interrupts = <28>;
resets = <&rcc 257>;
clocks = <&rcc 513>;
status = "disabled";
};
However we could perhaps be more literate even if we don't use the macros?
timer3: timer@40000000 {
compatible = "st,stm32-timer";
reg = <0x40000000 0x400>;
interrupts = <28>;
resets = <&rcc ((0x20*8) + 1)>;
clocks = <&rcc ((0x40*8) + 1)>;
status = "disabled";
};
Daniel.
Kind regards,
Maxime
Arnd
[0]: http://lkml.iu.edu/hypermail/linux/kernel/1504.3/04523.html
[1]: http://www.st.com/web/en/resource/technical/document/reference_manual/DM00031020.pdf
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