On Mon, 7 Jan 2019 14:01:01 +0100 Maxime Ripard maxime.ripard@bootlin.com wrote:
Hi,
On Mon, Jan 07, 2019 at 01:03:33AM +0000, André Przywara wrote:
On 31/12/2018 16:59, Jagan Teki wrote:
Clock control unit comprises of parent clocks, gates, multiplexers, dividers, multipliers, pre/post dividers and flags etc.
So, the U-Boot implementation of ccu has divided into gates and tree. gates are generic clock configuration of enable/disable bit management which can be handle via ccu_clock_gate.
So if I understand this correctly, you implement the gate functionality separately from the complex clock code, even if they are the same clock from the DT point of view? So if one wants to enable the MMC0 clock, which is a mux/divider clock, one needs to specify an extra entry in the gate array to describe the enable bit in this special clock register? Sounds a bit surprising, but is probably a neat trick to keep things simple. There should be a comment in the code to this regard then.
Tree clocks are parent clock type, fixed clocks, mp, nk, nkm, nkmp, pre/post div, flags etc. which were managed via ccu_clock_tree.
For a start, can we use more descriptive names than those very specific MP/NK names? DIV_MUX and PLL sound more descriptive to me. I understand that Linux uses those terms, but it would be great if uninitiated people have a chance to understand this as well.
This patch add support for MP, NK, MISC, FIXED clock types as part of ccu clock tree with get_rate functionality this eventually used by uart driver. and rest of the infrastructure will try to add while CLK is being used on respective peripherals.
Note that few of the tree type clock would require to enable gates on their specific clock, in that case we need to add the gate details via ccu_clock_gate, example: MP with gate so the gate offset, bit value should add as part of ccu_clock_gate.
Signed-off-by: Jagan Teki jagan@amarulasolutions.com
arch/arm/include/asm/arch-sunxi/ccu.h | 192 +++++++++++++++++++++++++- drivers/clk/sunxi/clk_a64.c | 40 ++++++ drivers/clk/sunxi/clk_sunxi.c | 182 ++++++++++++++++++++++++ 3 files changed, 413 insertions(+), 1 deletion(-)
diff --git a/arch/arm/include/asm/arch-sunxi/ccu.h b/arch/arm/include/asm/arch-sunxi/ccu.h index 3fdc26978d..61b8c36b3b 100644 --- a/arch/arm/include/asm/arch-sunxi/ccu.h +++ b/arch/arm/include/asm/arch-sunxi/ccu.h @@ -7,15 +7,204 @@ #ifndef _ASM_ARCH_CCU_H #define _ASM_ARCH_CCU_H
+#define OSC_32K_ULL 32000ULL
32768
And why ULL? The whole Allwinner clock system works with 32-bit values, so just U would be totally sufficient. This avoid blowing this up to 64 bit unnecessarily, which sounds painful for those poor ARMv7 parts.
+#define OSC_24M_ULL 24000000ULL
+/**
- enum ccu_clk_type - ccu clock types
- @CCU_CLK_TYPE_MISC: misc clock type
What is MISC, exactly? Seems like an artefact clock to me, some placeholder you need because gate clocks are handled separately in the gates struct. Should this be called something with SIMPLE instead, or GATE?
- @CCU_CLK_TYPE_FIXED: fixed clock type
- @CCU_CLK_TYPE_MP: mp clock type
- @CCU_CLK_TYPE_NK: nk clock type
What is the point of those comments, as you are basically repeating the enum name? What about:
- @CCU_CLK_TYPE_PLL: PLL clock with two multiplier
fields
We have PLL with 2 multipliers, but also others with other factors sets, so that will end up being confusing. If the MP, NK and so on stuff is confusing, maybe we should just add a comment on top of that structure to explain what those factors are and what it actually means?
Fair enough, or we name it CCU_CLK_TYPE_PLL_NK, because this is what this type deals with. Point is that by chance I happened to know about those naming of factors in the manual, but other might be lost by just seeing "mp" or "nk", without any explanation - and the comment doesn't help here at all.
The other part is that the "TYPE_MP" is twice as confusing, as it can perfectly describe the MMC clocks, which use "N" and "M" in the A64 manual, for instance. That's why my suggestion for calling a spade a spade and saying it's a divider clock with a multiplexer. Happy to have the Linux naming in the comments.
Thanks, Andre.