Re: [PATCH 02/10] ata: ahci: Replace deprecated PCI functions

[Philipp Stanner <pstanner@redhat.com>]

On Fri, 2024-10-25 at 18:55 +0300, Ilpo Järvinen wrote:
> On Fri, 25 Oct 2024, Philipp Stanner wrote:
> 
> > pcim_iomap_regions_request_all() and pcim_iomap_table() have been
> > deprecated by the PCI subsystem in commit e354bb84a4c1 ("PCI:
> > Deprecate
> > pcim_iomap_table(), pcim_iomap_regions_request_all()").
> > 
> > Replace these functions with their successors, pcim_iomap() and
> > pcim_request_all_regions().
> > 
> > Signed-off-by: Philipp Stanner <pstanner@redhat.com>
> > Acked-by: Damien Le Moal <dlemoal@kernel.org>
> > ---
> >  drivers/ata/acard-ahci.c | 6 ++++--
> >  drivers/ata/ahci.c       | 6 ++++--
> >  2 files changed, 8 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/ata/acard-ahci.c b/drivers/ata/acard-ahci.c
> > index 547f56341705..3999305b5356 100644
> > --- a/drivers/ata/acard-ahci.c
> > +++ b/drivers/ata/acard-ahci.c
> > @@ -370,7 +370,7 @@ static int acard_ahci_init_one(struct pci_dev
> > *pdev, const struct pci_device_id
> >  	/* AHCI controllers often implement SFF compatible
> > interface.
> >  	 * Grab all PCI BARs just in case.
> >  	 */
> > -	rc = pcim_iomap_regions_request_all(pdev, 1 <<
> > AHCI_PCI_BAR, DRV_NAME);
> > +	rc = pcim_request_all_regions(pdev, DRV_NAME);
> >  	if (rc == -EBUSY)
> >  		pcim_pin_device(pdev);
> >  	if (rc)
> > @@ -386,7 +386,9 @@ static int acard_ahci_init_one(struct pci_dev
> > *pdev, const struct pci_device_id
> >  	if (!(hpriv->flags & AHCI_HFLAG_NO_MSI))
> >  		pci_enable_msi(pdev);
> >  
> > -	hpriv->mmio = pcim_iomap_table(pdev)[AHCI_PCI_BAR];
> > +	hpriv->mmio = pcim_iomap(pdev, AHCI_PCI_BAR, 0);
> > +	if (!hpriv->mmio)
> > +		return -ENOMEM;
> >  
> >  	/* save initial config */
> >  	ahci_save_initial_config(&pdev->dev, hpriv);
> > diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> > index 45f63b09828a..2043dfb52ae8 100644
> > --- a/drivers/ata/ahci.c
> > +++ b/drivers/ata/ahci.c
> > @@ -1869,7 +1869,7 @@ static int ahci_init_one(struct pci_dev
> > *pdev, const struct pci_device_id *ent)
> >  	/* AHCI controllers often implement SFF compatible
> > interface.
> >  	 * Grab all PCI BARs just in case.
> >  	 */
> > -	rc = pcim_iomap_regions_request_all(pdev, 1 <<
> > ahci_pci_bar, DRV_NAME);
> > +	rc = pcim_request_all_regions(pdev, DRV_NAME);
> >  	if (rc == -EBUSY)
> >  		pcim_pin_device(pdev);
> >  	if (rc)
> > @@ -1893,7 +1893,9 @@ static int ahci_init_one(struct pci_dev
> > *pdev, const struct pci_device_id *ent)
> >  	if (ahci_sb600_enable_64bit(pdev))
> >  		hpriv->flags &= ~AHCI_HFLAG_32BIT_ONLY;
> >  
> > -	hpriv->mmio = pcim_iomap_table(pdev)[ahci_pci_bar];
> > +	hpriv->mmio = pcim_iomap(pdev, ahci_pci_bar, 0);
> > +	if (!hpriv->mmio)
> > +		return -ENOMEM;
> 
> Hi,
> 
> I've probably lost the big picture somewhere and the coverletter
> wasn't 
> helpful focusing only the most immediate goal of getting rid of the 
> deprecated function.
> 
> These seem to only pcim_iomap() a single BAR. So my question is, what
> is 
> the reason for using pcim_request_all_regions() and not 
> pcim_request_region() as mentioned in the commit message of the
> commit 
> e354bb84a4c1 ("PCI: Deprecate pcim_iomap_table(), 
> pcim_iomap_regions_request_all()")?

That commit message isn't that precise and / or was written when
pcim_request_all_regions() was still an internal helper function.

> 
> I understand it's strictly not wrong to use
> pcim_request_all_regions()
> but I'm just trying to understand the logic behind the selection.
> I'm sorry if this is a stupid question, it's just what I couldn't
> figure 
> out on my own while trying to review these patches.
> 

The reason pcim_request_all_regions() is used in the entire series is
to keep behavior of the drivers 100% identical.
pcim_iomap_regions_request_all() performs a region request on *all* PCI
BARs and then ioremap()s *specific* ones; namely those set by the
barmask.

It seems to me that those drivers were only using
pcim_iomap_regions_request_all() precisely because of that feature:
they want to reserve all BARs through a region request. You could do
that manually with

for (int i = 0; i < PCI_STD_NUM_BARS; i++) pcim_request_region();
mem = pcim_iomap(...);

When you look at Patch #10 you'll see the implementation of
pcim_iomap_regions_request_all() and will discover that it itself uses
pcim_request_all_regions().

So you could consider this series a partial code-move that handily also
gets rid of a complicated function that prevents us from removing,
ultimately, the problematic function pcim_iomap_table().


Hope this helps,
P.

> (I admit not reading all the related discussions in the earlier
> versions.)
>