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

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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@xxxxxxxxxx>
---
  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
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