Messages in this thread | | | Date | Wed, 22 Nov 2023 11:46:14 +0100 | Subject | Re: [PATCH v2 1/7] dt-bindings: usb: ti,j721e-usb: add ti,j7200-usb compatible | From | Théo Lebrun <> |
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Hello,
On Tue Nov 21, 2023 at 6:11 PM CET, Krzysztof Kozlowski wrote: > On 21/11/2023 17:53, Théo Lebrun wrote: > > On Mon Nov 20, 2023 at 6:32 PM CET, Krzysztof Kozlowski wrote: > >> On 20/11/2023 18:06, Théo Lebrun wrote: > >>> On this platform, the controller & its wrapper are reset on resume. This > >>> makes it have a different behavior from other platforms. > >>> > >>> We allow using the new compatible with a fallback onto the original > >>> ti,j721e-usb compatible. We therefore allow using an older kernel with > >> > >> Where is fallback ti,j721e-usb used? Please point me to the code. > > > > No fallback is implemented in code. Using a kernel that doesn't have > > this patch series but a more recent devicetree: DT has both > > devicetrees & the kernel will know which driver to use. > > I meant your bindings. You said - with fallback to ti,j721e-usb. I do > not see it. To me the commit description is not accurate.
I see your point, I'll remove that aspect.
> > That is opposed to having only compatible = "ti,j7200-usb". If using an > > old kernel, it would not know what driver to match it to. > > > > [...] > > > >>> --- a/Documentation/devicetree/bindings/usb/ti,j721e-usb.yaml > >>> +++ b/Documentation/devicetree/bindings/usb/ti,j721e-usb.yaml > >>> @@ -12,11 +12,15 @@ maintainers: > >>> properties: > >>> compatible: > >>> oneOf: > >>> + - const: ti,j7200-usb > >>> - const: ti,j721e-usb > >>> - const: ti,am64-usb > >>> - items: > >>> - const: ti,j721e-usb > >>> - const: ti,am64-usb > >>> + - items: > >>> + - const: ti,j721e-usb > >> > >> This makes little sense. It's already on the list. Twice! Don't add it > >> third time. > >> > >> I am sorry, but this binding makes no sense. I mean, existing binding > >> makes no sense, but your change is not making it anyhow better. > > > > The goal of the DT schema pre-patch was to allow all three: > > > > compatible = "ti,j721e-usb"; > > compatible = "ti,am64-usb"; > > compatible = "ti,j721e-usb", "ti,am64-usb"; > > Which does not make sense. > > How ti,j721e-usb can be and cannot be compatible with am64 in the same time?
The code tells us that there is no difference between ti,j721e-usb & ti,am64-usb. And the commit adding the of_device_id entry agrees, see 4f30b9d2315f (usb: cdns3: Add support for TI's AM64 SoC, 2021-01-19). Here is the entire patch because it is so small:
diff --git a/drivers/usb/cdns3/cdns3-ti.c b/drivers/usb/cdns3/cdns3-ti.c index 90e246601537..eccb1c766bba 100644 --- a/drivers/usb/cdns3/cdns3-ti.c +++ b/drivers/usb/cdns3/cdns3-ti.c @@ -214,6 +214,7 @@ static int cdns_ti_remove(struct platform_device *pdev)
static const struct of_device_id cdns_ti_of_match[] = { { .compatible = "ti,j721e-usb", }, + { .compatible = "ti,am64-usb", }, {}, }; MODULE_DEVICE_TABLE(of, cdns_ti_of_match);
> > I've followed the same scheme & added both of those: > > > > compatible = "ti,j7200-usb"; > > compatible = "ti,j7200-usb", "ti,j721e-usb"; > > > > I messed up the ordering in the added 'items' options, but the logic > > seems right to me. And dtbs_check agrees. Am I missing something? > > Logic is wrong. Device either is or is not compatible with something. At > least usually. We have some exceptions like SMMU for Adreno. Is this the > case? Why the device is and is not compatible with some other variant?
My understanding is this: j721e & am64 are strictly equivalent. On our j7200 we know we reset on resume. I see three ways forward:
- properties: compatible: oneOf: - const: ti,j7200-usb - const: ti,j721e-usb - const: ti,am64-usb
We keep both ti,j721e-usb & ti,am64-usb separate even though they are compatible. It makes for simpler changes & it avoids touching devicetrees.
- properties: compatible: oneOf: - const: ti,j7200-usb - const: ti,j721e-usb
AM64 is a duplicate of J721E. Remove it and update upstream devicetrees.
- properties: compatible: oneOf: - const: ti,j7200-usb - items: - const: ti,j721e-usb - const: ti,am64-usb
J721E & AM64 are compatible, express that & update devicetrees.
Option one is simpler & doesn't change devicetrees so I'd lean in that direction. What's your opinion?
Regards,
-- Théo Lebrun, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
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