Re: [PATCH v2 0/2] Support BMG PMT features for Xe

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Wed, Nov 13, 2024 at 10:40:42AM -0800, David E. Box wrote:
> On Wed, 2024-11-13 at 15:52 +0200, Ilpo Järvinen wrote:
> > On Wed, 13 Nov 2024, Andy Shevchenko wrote:
> > > On Tue, Nov 12, 2024 at 11:30:33AM -0500, Michael J. Ruhl wrote:
> > > > Updates for PMT to support user offsets from the sysfs API.
> > > > 
> > > > Addressed review comments for the Xe driver udpates.
> > > 
> > > FWIW,
> > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > > 
> > > If you have wish and time, there are problems with the drivers of different
> > > severities (from "fine as is" to "good to be fixed, but okay as is") I have
> > > noticed so far:
> > > - it uses s*printf() instead of sysfs_emit*()
> > > - it most likely never tested the corner cases. e.g.,
> > > 
> > > 	if (disc_res->start >= pci_resource_start(pci_dev, i) &&
> > > 	    (disc_res->start <= pci_resource_end(pci_dev, i))) {
> > > 
> > >   what is this supposed to mean? Probably someone wanted resource_contains()
> > > or
> > >   alike to be called here.
> 
> This is a corner case that occurs for devices that are non-compliant, in this
> case meaning devices that don't follow our PMT spec convention of specifying
> which BAR an address belongs to. Without this information, we have to deduce the
> BAR manually to access other needed registers that are offset from the base of
> that BAR.

What I am pointing out is that we compare start address (and only start!) to
both, start _and_ end of the given resource. So currently the second check is
redundant and that looks suspicious. I believe one wanted to have

	if (disc_res->start >= pci_resource_start(pci_dev, i) &&
	    (disc_res->end <= pci_resource_end(pci_dev, i))) {

(note end!) and if using helpers, this would never happened :-)

> I can change this to use resource_contains().

Please, will clarify the above confusion..

> > > - slightly above the above piece the for-loop
> > > 
> > > 	for (i = 0; i < 6; i++)
> > > 
> > >   which probably want to use PCI_STD_RESOURCE_END)
> > 
> > While both work, in practice PCI_STD_NUM_BARS is way more common than 
> > PCI_STD_RESOURCE_END.
> 
> Will change this too. Thanks.

You are welcome!

-- 
With Best Regards,
Andy Shevchenko