From: Niklas Cassel <cassel@kernel•org>
To: Koichiro Den <den@valinux•co.jp>
Cc: jingoohan1@gmail•com, mani@kernel•org, lpieralisi@kernel•org,
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Subject: Re: [PATCH v9 4/5] PCI: dwc: ep: Support BAR subrange inbound mapping via Address Match Mode iATU
Date: Fri, 23 Jan 2026 09:51:19 +0100 [thread overview]
Message-ID: <aXM2hwCrziK2I8OL@ryzen> (raw)
In-Reply-To: <l7wknbayighcczjkqfwhbaqrepjtbgxxstgkntoqvnrs7dnm6g@wvmy67ky37pv>
On Fri, Jan 23, 2026 at 10:16:21AM +0900, Koichiro Den wrote:
> >
> > There might be other EPC drivers that don't disable all BARs in their .init(), so I would say that simply checking if the BAR has an address is not sufficient to guarantee that an EPF driver has called set_bar().
> >
>
> Even if an EPC driver does not reset the BAR in their .init() and some
> default translation is left exposed, wouldn't it be safe as long as
> dw_pcie_ep_ib_atu_addr() succeeds in programming inbound mappings for the
> entire BAR?
For e.g. on RK3588, the default HW configuration of the DWC controller has
all 5 BARs as enabled, with a size of 1 GB.
There is no inbound address translation for these BARs by default.
So for it to be safe, the size of the set_bar() call would have to
match the current size of the BAR, but how should the EPF driver know
that when it has not called set_bar() yet?
dw_pcie_ep_read_bar_assigned() does not return the current size of the
BAR. So you can't verify that the set_bar() call has the same size as
the BARs "default size".
>
> That said, such usage apparently contradicts the documented usage (1st
> set_bar with no submap, then with submap) described in the docs and commit
> messages in this series, and allowing it would make things unnecessarily
> complicated. So I agree that adding such a safeguard is the right approach.
>
> >
> > I think the safest option is my second suggestion because then we know that we will only call
> > dw_pcie_ep_ib_atu_addr()
> >
> > When:
> >
> > 1) If ep->epf_bar[bar] is set:
> > https://github.com/torvalds/linux/blob/v6.19-rc6/drivers/pci/controller/dwc/pcie-designware-ep.c#L363
> >
> >
> > 2) All the other requirements to dynamically update a BAR is also met:
> >
> > https://github.com/torvalds/linux/blob/v6.19-rc6/drivers/pci/controller/dwc/pcie-designware-ep.c#L368-L370
> >
>
> That makes sense, and it ensures that the behavior always accords with the
> docs and commit messages in this series.
I think it makes most sense to put the "use_addr_translation = true"
after the check:
/*
* We can only dynamically change a BAR if the new BAR size and
* BAR flags do not differ from the existing configuration.
*/
if (ep->epf_bar[bar]->barno != bar ||
ep->epf_bar[bar]->size != size ||
ep->epf_bar[bar]->flags != flags)
return -EINVAL;
So we know that dw_pcie_ep_ib_atu_addr() is only called when the size is the
same.
Kind regards,
Niklas
next prev parent reply other threads:[~2026-01-23 8:51 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-22 8:49 [PATCH v9 0/5] PCI: endpoint: BAR subrange mapping support Koichiro Den
2026-01-22 8:49 ` [PATCH v9 1/5] PCI: endpoint: Add dynamic_inbound_mapping EPC feature Koichiro Den
2026-01-22 8:49 ` [PATCH v9 2/5] PCI: endpoint: Add BAR subrange mapping support Koichiro Den
2026-01-22 9:03 ` Niklas Cassel
2026-01-22 8:49 ` [PATCH v9 3/5] PCI: dwc: Advertise dynamic inbound " Koichiro Den
2026-01-22 9:00 ` Niklas Cassel
2026-01-22 8:49 ` [PATCH v9 4/5] PCI: dwc: ep: Support BAR subrange inbound mapping via Address Match Mode iATU Koichiro Den
2026-01-22 9:23 ` Niklas Cassel
2026-01-22 14:29 ` Koichiro Den
2026-01-22 16:59 ` Niklas Cassel
2026-01-23 1:16 ` Koichiro Den
2026-01-23 8:51 ` Niklas Cassel [this message]
2026-01-23 14:28 ` Koichiro Den
2026-01-24 14:22 ` Koichiro Den
2026-01-22 8:49 ` [PATCH v9 5/5] Documentation: PCI: endpoint: Clarify pci_epc_set_bar() usage Koichiro Den
2026-01-22 9:07 ` Niklas Cassel
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