Re: [PATCH] arm64: tegra: Fix CPU compatible string for Tegra132

[Joseph Lo <josephl-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On 05/25/2016 11:42 PM, Stephen Warren wrote:
> On 05/24/2016 08:11 PM, Joseph Lo wrote:
>> On 05/23/2016 03:42 PM, Joseph Lo wrote:
>>> As per commit f634da375fc96 ("Documentation: DT bindings: add nvidia,
>>> tegra132-denver compatible string"), fixing the CPU compatible string
>>> for
>>> Tegra132 to match the binding document currently.
>>>
>>> Signed-off-by: Joseph Lo <josephl-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
>>> ---
>>>   arch/arm64/boot/dts/nvidia/tegra132.dtsi | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/arm64/boot/dts/nvidia/tegra132.dtsi
>>> b/arch/arm64/boot/dts/nvidia/tegra132.dtsi
>>> index 2013f8916084..7b1cdc029de3 100644
>>> --- a/arch/arm64/boot/dts/nvidia/tegra132.dtsi
>>> +++ b/arch/arm64/boot/dts/nvidia/tegra132.dtsi
>>> @@ -964,13 +964,13 @@
>>>
>>>           cpu@0 {
>>>               device_type = "cpu";
>>> -            compatible = "nvidia,denver", "arm,armv8";
>>> +            compatible = "nvidia,tegra132-denver", "arm,armv8";
>>
>> Hi Stephen, Thierry,
>>
>> Should we fix this or fix the compatible string in the binding document
>> as just "nvidia,denver" to represent all the Devner CPU revisions just
>> like some other CPUs did? e.g. arm,cortex-a57, which represents all the
>> A57 revisions.
>
> I would expect compatible to be:
>
> compatible = "nvidia,tegra132-denver", "nvidia,denver", "arm,armv8";

Because we don't have "nvidia,denver" binding in the document, to do 
what you said, supposely I should add that first and fix the binding for 
Tegra132, right?

>
> The "nvidia,denver" entry is already present, and hence probably
> shouldn't be removed. It can represent "Denver 1.0". We should add the
> T132 entry to indicate the specific implementation. Admittedly right now
> there's a 1:1 relation between SoC and Denver version. Either/both of
> those could in theory be required to trigger specific bug-fixes/WARs.
>
> For later chips which have a different Denver version, I'd expect to see
> something like:
>
> compatible = "nvidia,tegraNNN-denver", "nvidia,denverMMM", "arm,armv8";
>
> ... where NNN is the SoC version/name and MMM is the Denver version.
> There could be extra entries in the property if the new versions are
> backwards-compatible with old versions.

Because it's 1:1 relationship, if we have new cores coming later, we 
should add both of the compatible string of SoC version and CPU core 
version in the ARM CPU binding document, is that correct?

Thanks,
Joseph