linux-kernel - [PATCH 2/3] PCI: of: avoid 'devm_pci_remap_iospace' if PCI

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Date:   Sat,  7 Aug 2021 09:24:08 +0200
From:   Sergio Paracuellos <sergio.paracuellos@...il.com>
To:     tsbogend@...ha.franken.de
Cc:     bhelgaas@...gle.com, matthias.bgg@...il.com,
        gregkh@...uxfoundation.org, linux-mips@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-staging@...ts.linux.dev,
        neil@...wn.name, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] PCI: of: avoid 'devm_pci_remap_iospace' if PCI_IOBASE is not defined

Defining PCI_IOBASE for MIPS ralink in expected addresses results in PCI IO
resources being assigned but the addresses generated for IO accesses are wrong
since the ioremap in the PCI core function 'pci_parse_request_of_pci_ranges'
tries to remap to a fixed virtual address (PC_IOBASE) which can't work for KSEG1
addresses. To get it working this way, we would need to put PCI_IOBASE somewhere
into KSEG2 which will result in creating TLB entries for IO addresses, which most
of the time isn't needed on MIPS because of access via KSEG1. To allow MIPS PCI
drivers to properly use the PCI generic core we need to increase IO_SPACE_LIMIT
since IO addresses are in addresses higher that 0xffff. We also need to avoid
the call 'devm_pci_remap_iospace' when 'pci_parse_request_of_pci_ranges' is
called to avoid the following problem:

------------[ cut here ]------------
WARNING: CPU: 2 PID: 1 at ../drivers/pci/pci.c:4066 pci_remap_iospace+0x3c/0x54
This architecture does not support memory mapped I/O
Modules linked in:
CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.10.1+ #1228
Stack : 00000000 00000000 807fa974 00000000 827ffa80 80066b48 80710000 0000000b
        00000000 00000000 81c59aac 7d06ddec 80850000 00000001 81c59a40 7d06ddec
        00000000 00000000 807c909c 81c598f0 00000001 81c59904 00000000 0000000a
        203a6d6d 80708880 0000000f 70617773 80850000 00000000 00000000 807d0000
        807ffecc 1e160000 00000001 00000200 00000000 8054e920 00000008 815e0008
        ...
Call Trace:
[<80008efc>] show_stack+0x8c/0x130
[<806e1674>] dump_stack+0x9c/0xc8
[<80024a3c>] __warn+0xc0/0xe8
[<80024ad0>] warn_slowpath_fmt+0x6c/0xbc
[<80410ca8>] pci_remap_iospace+0x3c/0x54
[<80410d20>] devm_pci_remap_iospace+0x58/0xa4
[<8042019c>] devm_of_pci_bridge_init+0x4dc/0x55c
[<80408de8>] devm_pci_alloc_host_bridge+0x78/0x88
[<80424e44>] mt7621_pci_probe+0x68/0x9a4
[<80464804>] platform_drv_probe+0x40/0x7c
[<804628bc>] really_probe+0x2fc/0x4e4
[<80463214>] device_driver_attach+0x4c/0x74
[<80463384>] __driver_attach+0x148/0x150
[<8046047c>] bus_for_each_dev+0x6c/0xb0
[<804614dc>] bus_add_driver+0x1b4/0x1fc
[<80463aa0>] driver_register+0xd0/0x110
[<80001714>] do_one_initcall+0x84/0x1c0
[<808e7fd0>] kernel_init_freeable+0x214/0x24c
[<806e4164>] kernel_init+0x14/0x118
[<80003358>] ret_from_kernel_thread+0x14/0x1c

---[ end trace 1c9d4412bd51b53c ]---
mt7621-pci 1e140000.pcie: error -19: failed to map resource [io  0x1e160000-0x1e16ffff]

Hence don't call 'devm_pci_remap_iospace' if PCI_IOBASE is not defined to get
a working PCI core APIs for MIPS ralink platforms.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@...il.com>
---
 drivers/pci/of.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index a143b02b2dcd..657aef39bf63 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -564,12 +564,14 @@ static int pci_parse_request_of_pci_ranges(struct device *dev,
 
 		switch (resource_type(res)) {
 		case IORESOURCE_IO:
+#ifdef PCI_IOBASE
 			err = devm_pci_remap_iospace(dev, res, iobase);
 			if (err) {
 				dev_warn(dev, "error %d: failed to map resource %pR\n",
 					 err, res);
 				resource_list_destroy_entry(win);
 			}
+#endif
 			break;
 		case IORESOURCE_MEM:
 			res_valid |= !(res->flags & IORESOURCE_PREFETCH);
-- 
2.25.1