[PATCH v4 5/5] arm64: dts: Add dts files for Hisilicon Hi6220 SoC

[mark.rutland@arm.com (Mark Rutland)]

On Wed, May 06, 2015 at 07:50:52AM +0100, Bintian wrote:
> Hello Mark,
> 
> On 2015/5/6 11:16, Bintian wrote:
> > Hello Mark,
> >
> > On 2015/5/6 1:13, Mark Rutland wrote:
> [...]
> >>> +        uart0: uart at f8015000 {    /* console */
> >>> +            compatible = "arm,pl011", "arm,primecell";
> >>> +            reg = <0x0 0xf8015000 0x0 0x1000>;
> >>> +            interrupts = <GIC_SPI 36 IRQ_TYPE_LEVEL_HIGH>;
> >>> +            clocks = <&ao_ctrl HI6220_UART0_PCLK>, <&ao_ctrl
> >>> HI6220_UART0_PCLK>;
> >>> +            clock-names = "uartclk", "apb_pclk";
> >>> +        };
> >>
> >> In a previous discussion [1] the UART on HI6220 was described as not
> >> fully PL011 compliant, with a number of differences (e.g. the FIFO
> >> length).
> >>
> >> Given that, I feel somewhat uncomfortable with the current compatible
> >> string list. What exactly are those differences? We may need a more
> >> specific compatible string (even if in addition to those existing ones),
> >> or perhaps other properties.
> > The small system can be booted and the console also works well without
> > changing any code of driver amba-pl011.c, so I think the compatible
> > string is OK for this patch set.
> >
> > Hisilicon do some performance enhancements based on PL011, but the
> > current driver "amba-pl011.c" also works on hi6220 without those
> > enhancements driver code.
> Checked with Hisilicon chip designer, the UART0 is used for DEBUG
> console and compliant with PL011 fully.

I think that given that we know the UART is not quite a PL011 we should
add an additional compatible string just in case some difference crops
up later that is problematic.

So we'd have something like:

	compatible = "hisilicon,hi6220-uart", "arm,pl011", "arm,primecell";

That way we can add any optimisations or workarounds later as required.

Thanks,
Mark.