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Date:   Fri, 8 Jan 2021 15:20:21 -0600
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Michael Walle <michael@walle.cc>
Cc:     linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        intel-wired-lan@lists.osuosl.org,
        Bjorn Helgaas <bhelgaas@google.com>,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Tony Nguyen <anthony.l.nguyen@intel.com>,
        Paul Menzel <pmenzel@molgen.mpg.de>
Subject: Re: [PATCH v2] PCI: Fix Intel i210 by avoiding overlapping of BARs
Message-ID: <20210108212021.GA1472277@bjorn-Precision-5520>
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In-Reply-To: <20201230185317.30915-1-michael@walle.cc>
Precedence: bulk

On Wed, Dec 30, 2020 at 07:53:17PM +0100, Michael Walle wrote:
> The Intel i210 doesn't work if the Expansion ROM BAR overlaps with
> another BAR. Networking won't work at all and once a packet is sent the
> netdev watchdog will bite:

Hi Michael,

Sorry for the issue on your system and thanks for investigating it and
coming up with a patch to fix it!

1) Is this a regression?  It sounds like you don't know for sure
because earlier kernels don't support your platform.

2) Can you open a bugzilla at https://bugzilla.kernel.org and attach
the complete dmesg and "sudo lspci -vv" output?  I want to see whether
Linux is assigning something incorrectly or this is a consequence of
some firmware initialization.

3) If the Intel i210 is defective in how it handles an Expansion ROM
that overlaps another BAR, a quirk might be the right fix.  But my
guess is the device is working correctly per spec and there's
something wrong in how firmware/Linux is assigning things.  That would
mean we need a more generic fix that's not a quirk and not tied to the
Intel i210.

> [   89.059374] ------------[ cut here ]------------
> [   89.064019] NETDEV WATCHDOG: enP2p1s0 (igb): transmit queue 0 timed out
> [   89.070681] WARNING: CPU: 1 PID: 0 at net/sched/sch_generic.c:443 dev_watchdog+0x3a8/0x3b0
> [   89.078989] Modules linked in:
> [   89.082053] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G        W         5.11.0-rc1-00020-gc16f033804b #289
> [   89.091574] Hardware name: Kontron SMARC-sAL28 (Single PHY) on SMARC Eval 2.0 carrier (DT)
> [   89.099870] pstate: 60000005 (nZCv daif -PAN -UAO -TCO BTYPE=--)
> [   89.105900] pc : dev_watchdog+0x3a8/0x3b0
> [   89.109923] lr : dev_watchdog+0x3a8/0x3b0
> [   89.113945] sp : ffff80001000bd50
> [   89.117268] x29: ffff80001000bd50 x28: 0000000000000008
> [   89.122602] x27: 0000000000000004 x26: 0000000000000140
> [   89.127935] x25: ffff002001c6c000 x24: ffff002001c2b940
> [   89.133267] x23: ffff8000118c7000 x22: ffff002001c6c39c
> [   89.138600] x21: ffff002001c6bfb8 x20: ffff002001c6c3b8
> [   89.143932] x19: 0000000000000000 x18: 0000000000000010
> [   89.149264] x17: 0000000000000000 x16: 0000000000000000
> [   89.154596] x15: ffffffffffffffff x14: 0720072007200720
> [   89.159928] x13: 0720072007740775 x12: ffff80001195b980
> [   89.165260] x11: 0000000000000003 x10: ffff800011943940
> [   89.170592] x9 : ffff800010100d44 x8 : 0000000000017fe8
> [   89.175924] x7 : c0000000ffffefff x6 : 0000000000000001
> [   89.181255] x5 : 0000000000000000 x4 : 0000000000000000
> [   89.186587] x3 : 00000000ffffffff x2 : ffff8000118eb908
> [   89.191919] x1 : 84d8200845006900 x0 : 0000000000000000
> [   89.197251] Call trace:
> [   89.199701]  dev_watchdog+0x3a8/0x3b0
> [   89.203374]  call_timer_fn+0x38/0x208
> [   89.207049]  run_timer_softirq+0x290/0x540
> [   89.211158]  __do_softirq+0x138/0x404
> [   89.214831]  irq_exit+0xe8/0xf8
> [   89.217981]  __handle_domain_irq+0x70/0xc8
> [   89.222091]  gic_handle_irq+0xc8/0x2b0
> [   89.225850]  el1_irq+0xb8/0x180
> [   89.228999]  arch_cpu_idle+0x18/0x40
> [   89.232587]  default_idle_call+0x70/0x214
> [   89.236610]  do_idle+0x21c/0x290
> [   89.239848]  cpu_startup_entry+0x2c/0x70
> [   89.243783]  secondary_start_kernel+0x1a0/0x1f0
> [   89.248332] ---[ end trace 1687af62576397bc ]---
> [   89.253350] igb 0002:01:00.0 enP2p1s0: Reset adapter

This entire splat is overkill.  The useful part is what somebody who
trips over this might google for.  Strip out the "cut here", the
timestamps, the register dump, and the last 6-8 lines of the call
trace.

> Before this fixup the Expansion ROM BAR will overlap with BAR3:
>   # lspci -ns 2:1:0 -xx
>   0002:01:00.0 0200: 8086:1533 (rev 03)
>   00: 86 80 33 15 06 04 10 00 03 00 00 02 08 00 00 00
>   10: 00 00 00 40 00 00 00 00 00 00 00 00 00 00 20 40
>   20: 00 00 00 00 00 00 00 00 00 00 00 00 3c 10 03 00
>   30: 00 00 20 40 40 00 00 00 00 00 00 00 22 01 00 00
> 
> Add a quirk which will update the Expansion ROM BAR for Intel i210s even
> if the ROM is disabled. After the quirk is applied:
>   # lspci -ns 2:1:0 -xx
>   0002:01:00.0 0200: 8086:1533 (rev 03)
>   00: 86 80 33 15 06 04 10 00 03 00 00 02 08 00 00 00
>   10: 00 00 00 40 00 00 00 00 00 00 00 00 00 00 20 40
>   20: 00 00 00 00 00 00 00 00 00 00 00 00 3c 10 03 00
>   30: 00 00 10 40 40 00 00 00 00 00 00 00 22 01 00 00
> 
> This behavior was seen with U-Boot v2021.01-rc3 on an ARM64 board (kontron
> sl28). Earlier versions likely behave in the same way, but the board which
> this was tested on, is only supported since the 2021.01 version.
> 
> Signed-off-by: Michael Walle <michael@walle.cc>
> ---
> 
> Paul, thanks for the fast first review!
> 
> changes since v1:
>  - more precise subject
>  - added info about bootloader
>  - fixed typos
>  - added lspci output to the commit message after the quirks is applied
>  - added pci_info() to inform about the quirk
>  - renamed pci_fixup_rewrite_rom_bar() to pci_fixup_write_rom_bar().
>    Technically, linux didn't write the ROM BAR yet.
> 
>  drivers/pci/quirks.c | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 653660e3ba9e..a1a904ed5a10 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -5612,3 +5612,39 @@ static void apex_pci_fixup_class(struct pci_dev *pdev)
>  }
>  DECLARE_PCI_FIXUP_CLASS_HEADER(0x1ac1, 0x089a,
>  			       PCI_CLASS_NOT_DEFINED, 8, apex_pci_fixup_class);
> +
> +/*
> + * Some devices don't work if the Expansion ROM has the same base address as
> + * one of the other BARs although it is disabled.
> + * This might happen if the bootloader/BIOS enumerates the BARs in a different
> + * way than linux. If the Expansion ROM is disabled, linux deliberately skips
> + * writing the ROM BAR if the BAR is not enabled because of some broken
> + * devices, see pci_std_update_resource(). Thus, the ROM BAR of the device will
> + * still contain the value assigned by the booloader, which might be the same
> + * value as one of the other BARs then.
> + *
> + * As a workaround, update the Expansion ROM BAR even if the Expansion ROM is
> + * disabled.
> + */
> +static void pci_fixup_write_rom_bar(struct pci_dev *dev)
> +{
> +	struct resource *res = &dev->resource[PCI_ROM_RESOURCE];
> +	struct pci_bus_region region;
> +	u32 rom_addr;
> +
> +	pci_read_config_dword(dev, dev->rom_base_reg, &rom_addr);
> +
> +	if (rom_addr & PCI_ROM_ADDRESS_ENABLE)
> +		return;
> +
> +	pci_info(dev, "Writing Expansion ROM BAR to avoid overlapping\n");
> +
> +	pcibios_resource_to_bus(dev->bus, &region, res);
> +	rom_addr &= ~PCI_ROM_ADDRESS_MASK;
> +	rom_addr |= region.start;
> +	pci_write_config_dword(dev, dev->rom_base_reg, rom_addr);
> +}
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x1533, pci_fixup_write_rom_bar);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x1536, pci_fixup_write_rom_bar);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x1537, pci_fixup_write_rom_bar);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL, 0x1538, pci_fixup_write_rom_bar);
> -- 
> 2.20.1
>