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

Marc Zyngier marc.zyngier at arm.com
Tue Jun 2 02:13:26 PDT 2015

On 02/06/15 09:59, Linus Walleij wrote:
> On Sat, May 30, 2015 at 3:50 AM, Bintian Wang <bintian.wang at huawei.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.
>> future optimisations or workarounds works.
>> Signed-off-by: Bintian Wang <bintian.wang at huawei.com>
>> Suggested-by: Mark Rutland <mark.rutland at arm.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.

That feels weird. This amba_vendor enum is not under control of the DT
author, nor the kernel. This is a set of codes that are managed by a
third party (probably ARM). What if some company with a name starting
with 'H' (Hilarious Inc?) comes up with some actual HW and ends up
conflicting with the above?


Jazz is not dead. It just smells funny...

More information about the linux-arm-kernel mailing list