[lkml]   [2016]   [May]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 2/2] irqchip/gic-v2m: Add workaround for Broadcom NS2 GICv2m erratum
Hi Marc,

On 5/4/2016 12:49 AM, Marc Zyngier wrote:
> On 04/05/16 00:47, Ray Jui wrote:
>> Alex Barba <> discovered Broadcom NS2 GICv2m
>> implementation has an erratum where the MSI data needs to be the SPI
>> number subtracted by an offset of 32, for the correct MSI interrupt to
>> be triggered.
>> We are aware that APM X-Gene GICv2m has a similar erratum where the
>> MSI data needs to be the offset from the spi_start. While APM's workaround
>> is triggered based on readings from the MSI_IIDR register, this patch
>> contains a more general solution by allowing this offset to be
>> specified with an optional DT property 'arm,msi-offset-spi'. This patch
>> also maintains compatibility with existing APM platforms
> It may be more generic, but it also fails to deal with less capable
> firmware implementations. In contrast, reading MSI_IIDR is always
> possible (assuming you have a unique ID for this v2m implementation).
> If you cannot uniquely identify it using an ID register, the usual
> alternative is to have a new "compatible" string identifying the
> defective part, and set the offset based on this string. This still
> fails the ACPI test, but is the least invasive DT-wise.

Okay. We do seem to have an ID. The JEP code looks a bit weird as the
IIDR register reads 0x13f. We were just a bit concerned that there's
another chip from Broadcom that may happen to have the same ID but may
already have this offset issue fixed (or made worse with a different
offset, :) ). Since that chip has not even taped out yet, we can wait
till later to confirm. If a compatible string is needed in the future,
we'll add that.

For now, I'm going to submit another patch to deal with this offset
based on IIDR reading 0x13f.

> Thanks,
> M.



 \ /
  Last update: 2016-05-04 18:41    [W:0.080 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site