Re: [PATCH for-linus v3 1/2] PCI: Honor Max Link Speed when determining supported speeds

[Lukas Wunner <lukas@wunner.de>]

On Thu, Dec 19, 2024 at 08:43:57AM +0900, Krzysztof Wilczy??ski wrote:
> > > The GENMASK() macro used herein specifies 0 as lowest bit, even though
> > > the Supported Link Speeds Vector ends at bit 1.  This is done on purpose
> > > to avoid a GENMASK(0, 1) macro if Max Link Speed is zero.  That macro
> > > would be invalid as the lowest bit is greater than the highest bit.
> > > Ilpo has witnessed a zero Max Link Speed on Root Complex Integrated
> > > Endpoints in particular, so it does occur in practice.
> > 
> > Thanks for adding this extra information.
> > 
> > I'd also add reference to r6.2 section 7.5.3 which states those registers 
> > are required for RPs, Switch Ports, Bridges, and Endpoints _that are not 
> > RCiEPs_. My reading is that implies they're not required from RCiEPs.
> 
> Let me know how you would like to update the commit message.  I will do it
> directly on the branch.

FWIW, I edited the commit message like this on my local branch:

-Endpoints in particular, so it does occur in practice.
+Endpoints in particular, so it does occur in practice.  (The Link
+Capabilities Register is optional on RCiEPs per PCIe r6.2 sec 7.5.3.)

In other words, I just added the sentence in parentheses.
But maybe Ilpo has another wording preference... :)

Thanks,

Lukas