linux-kernel - Re: [PATCH v9 4/6] Documentation: DT: PL011: hi6220: add compatible string for Hisilicon designed UART

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Date:	Tue, 2 Jun 2015 18:55:20 +0800
From:	Bintian <bintian.wang@...wei.com>
To:	Linus Walleij <linus.walleij@...aro.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>
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	Will Deacon <will.deacon@....com>,
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	Rob Herring <robh+dt@...nel.org>,
	Paweł Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
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Subject: Re: [PATCH v9 4/6] Documentation: DT: PL011: hi6220: add compatible
 string for Hisilicon designed UART

On 2015/6/2 16:59, Linus Walleij wrote:
> On Sat, May 30, 2015 at 3:50 AM, Bintian Wang <bintian.wang@...wei.com> wrote:
>
>> Hisilicon does some performance enhancements based on PL011(e.g. larger
>> FIFO length), so add one compatible string "hisilicon,hi6220-uart" for
>
> That compatible string in the commit message is not even
> the same as in the patch.
The UART0 is PL011 compatible, the UART1/2 have some performance
enhancements features, so based on Mark's suggestion and I add this
compatible string just for future use.

>
>> future optimisations or workarounds works.
>>
>> Signed-off-by: Bintian Wang <bintian.wang@...wei.com>
>> Suggested-by: Mark Rutland <mark.rutland@....com>
>
> Maybe I missed out on the earlier conversation, but do you
> mean that the PrimeCell ID has not been properly set up
> to something unique in this HiSilicon version of the PL011
> block?
>
> Even if so: do not override the compatible string like this,
> that is not the PrimeCell style.
>
> Define an 8 bit vendor ID (like tha ASCII for 'H' 0x48
> or whatever) and encode it for these variants, if the
> hardware is just using the ARM default PrimeCell
> ID, override it in the device tree like Broadcom
> are doing in arch/arm/boot/dts/bcm2835.dtsi:
>
> arm,primecell-periphid = <0x00241011>;
>
> Maybe yours would be:
>
> arm,primecell-periphid = <0x00048011>;
>
> For a first HiSilicon variant, then do some
> <include/linux/amba/bus.h>:
>
> enum amba_vendor {
>          AMBA_VENDOR_ARM = 0x41,
> +       AMBA_VENDOR_HISILICON = 0x48,
>
> Then patch drivers/tty/serial/amba_pl011.c to add vendor_hisilicon
> and a match table for 0x00048011 just like everyone else.

Thanks and BR,

Bintian
> Yours,
> Linus Walleij
>
> .
>

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