Re: [PATCH v1 3/3] arm64: dts: add Hi6220 mailbox node

[Haojian Zhuang]

On Wed, 2015-08-26 at 00:00 +0800, Leo Yan wrote:
> On Tue, Aug 25, 2015 at 09:43:14PM +0800, Haojian Zhuang wrote:
> > On Tue, 2015-08-25 at 11:42 +0100, Mark Rutland wrote:
> > > > > Are you then going to hack GRUB, release a special HiKey version of
> > > > > GRUB, not support any other versions, and still can your firmware
> > > > > UEFI?
> > > > 
> > > > I don't need to hack GRUB at all.
> > > 
> > > Then it is working for you by pure chance alone.
> > > 
> > > Please listen to the advice you are being given here; we're trying to
> > > ensure that your platform functions (and continues to function) as best
> > > it can.
> > 
> > Since we discussed a lot on this, let's make a conclusion on it.
> > 
> > 1. UEFI could append the reserved buffer in it's memory mapping.
> > 2. These reserved buffer must be declared in DT, since we also need to
> >    support non-UEFI (uboot) at the same time.
> > 3. Mailbox node should reference reserved buffer by phandle in DT. Then
> >    map the buffer as non-cacheable in driver.
> > 4. These reserved buffer must use "no-map" property since it should be
> >    non-cacheable in driver.
> 
> For more specific discussion for DTS, i list two options at here;
> 
> - Option 1: just simply reserve memory regions through memory node,
>   and mailbox node will directly use the buffer through reg ranges;
> 
> - Option 2: use reserved-memory and mailbox node will refer phandle
>   of reserved-memory;
> 
> These two options both can work well with UEFI and Uboot, but option 1
> is more simple and straightforward; so i personally prefer it. But
> look forwarding your guys' suggestion.
> 
> Option 1:
> 
> 	memory@0 {
> 		device_type = "memory";
> 		reg = <0x00000000 0x00000000 0x00000000 0x05e00000>,
> 		      <0x00000000 0x05f00000 0x00000000 0x00eff000>,
> 		      <0x00000000 0x06e00000 0x00000000 0x0060f000>,
> 		      <0x00000000 0x07410000 0x00000000 0x38bf0000>;
> 	};
> 
>         [...]
> 
> 	mailbox: mailbox@f7510000 {
> 		#mbox-cells = <1>;
> 		compatible = "hisilicon,hi6220-mbox";
> 		reg = <0x0 0xf7510000 0x0 0x1000>, /* IPC_S */
> 		      <0x0 0x06dff800 0x0 0x0800>; /* Mailbox buffer */
> 		interrupts = <GIC_SPI 94 IRQ_TYPE_LEVEL_HIGH>;
> 	};
> 
> Option 2:
> 
> 	memory@0 {
> 		device_type = "memory";
> 		reg = <0x0 0x0 0x0 0x40000000>;
> 	};
> 
> 	reserved-memory {
> 		#address-cells = <2>;
> 		#size-cells = <2>;
> 		ranges;
> 
> 		mcu_reserved: mcu_reserved@06dff000 {
> 			no-map;
> 			reg = <0x0 0x06dff000 0x0 0x00001000>,	/* MCU mailbox buffer */
> 			      <0x0 0x05e00000 0x0 0x00100000>,	/* MCU firmware buffer */
> 			      <0x0 0x0740f000 0x0 0x00001000>;	/* MCU firmware section */
> 		};
> 	};
> 
>         [...]
> 
> 	mailbox: mailbox@f7510000 {
> 		#mbox-cells = <1>;
> 		compatible = "hisilicon,hi6220-mbox";
> 		reg = <0x0 0xf7510000 0x0 0x1000>; /* IPC_S */
> 		memory-region = <&mcu_reserved>;   /* Mailbox buffer */
> 		interrupts = <GIC_SPI 94 IRQ_TYPE_LEVEL_HIGH>;
> 	};

I prefer the second one. From my view, memory node should only describe
the hardware information of memory.

Regards
Haojian

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