On Fri, Mar 18, 2022 at 02:55:08AM +0530, Kuldeep Singh wrote:
On Thu, Mar 17, 2022 at 08:25:12PM +0000, Robin Murphy wrote:
On 2022-03-17 19:15, Kuldeep Singh wrote:
Renesas RZ/N1D platform uses compatible "arm,cortex-a7-timer" in
conjugation with "arm,armv7-timer". Since, initial entry is not
documented, it start raising dtbs_check warnings.
['arm,cortex-a7-timer', 'arm,armv7-timer'] is too long
'arm,cortex-a7-timer' is not one of ['arm,armv7-timer', 'arm,armv8-timer']
'arm,cortex-a7-timer' is not one of ['arm,cortex-a15-timer']
Document this compatible to address it. The motivation to add this
change is taken from an already existing entry "arm,cortex-a15-timer".
Please note, this will not hurt any arch timer users.
Eh, if it's never been documented or supported, I say just get rid of it.
The arch timer interface is by definition part of a CPU, and we can tell
what the CPU is by reading its ID registers. Indeed that's how the driver
handles the non-zero number of CPU-specific errata that already exist - we
don't need compatibles for that.
In some ways it might have been nice to have *SoC-specific* compatibles
given the difficulty some integrators seem to have had in wiring up a stable
count *to* the interface, but it's not like they could be magically added to
already-deployed DTs after a bug is discovered, and nor could we have
mandated them from day 1 just in case and subsequently maintained a binding
that is just an ever-growing list of every SoC. Oh well.
Robin, A similar discussion was already done on v1 thread. Please see
below for details:
https://lore.kernel.org/linux-devicetree/20220317065925.GA9158@9a2d8922b8f1/
https://lore.kernel.org/linux-devicetree/726bde76-d792-febf-d364-6eedeb748c3b@xxxxxxxxxxxxx/
And final outcome of discussion turns out to add this compatible string.
I agree with Robin on dropping. More specific here is not useful. If
we're going to add some cores, then we should add every core
implementation.
If one has a big.LITTLE system with A15/A7 what would be the right
compatible value?
I see people with different set of perspective in regard to whether keep
compatible string or not. We should have some sort of evidences to
support claims so that next time when similar situation arises, we'll be
aware beforehand how to proceed.
Every situation tends to be different.