linux-kernel - Re: [PATCH] ARM: dts: bcm2711-rpi-4-b: Fix pcie0's unit address

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Message-ID: <e1ca1f086c180f04044996ccf59981d59fbdbc6b.camel@redhat.com>
Date:   Mon, 30 Aug 2021 15:52:54 +0200
From:   nsaenzju@...hat.com
To:     Rob Herring <robh@...nel.org>
Cc:     f.fainelli@...il.com, gregkh@...uxfoundation.org,
        devicetree@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        stefan.wahren@...e.com
Subject: Re: [PATCH] ARM: dts: bcm2711-rpi-4-b: Fix pcie0's unit address

On Mon, 2021-08-30 at 08:39 -0500, Rob Herring wrote:
> On Mon, Aug 30, 2021 at 12:39:09PM +0200, Nicolas Saenz Julienne wrote:
> > dtbs_check currently complains that:
> > 
> > arch/arm/boot/dts/bcm2711-rpi-4-b.dts:220.10-231.4: Warning
> > (pci_device_reg): /scb/pcie@...00000/pci@1,0: PCI unit address format
> > error, expected "0,0"
> > 
> > Unsurprisingly pci@0,0 is the right address, as illustrated by its reg
> > property:
> > 
> > 	&pcie0 {
> > 		pci@0,0 {
> > 			/*
> > 			 * As defined in the IEEE Std 1275-1994 document,
> > 			 * reg is a five-cell address encoded as (phys.hi
> > 			 * phys.mid phys.lo size.hi size.lo). phys.hi
> > 			 * should contain the device's BDF as 0b00000000
> > 			 * bbbbbbbb dddddfff 00000000. The other cells
> > 			 * should be zero.
> > 			 */
> > 			reg = <0 0 0 0 0>;
> > 		};
> > 	};
> > 
> > The bus is clearly 0. So fix it.
> 
> s/bus/device/
> 
> The unit-address format is '<device>,<function>' (and function is 
> optional). The bus number is not part of the unit-address because that 
> is dynamic and then the path would not be fixed/known. The bus is part 
> of 'reg' for true OpenFirmware, but for FDT I think it should always be 
> 0 as the DT is static. 
> 
> Looks like the child node is wrong (both unit-address and reg) as well:
> 
>                 usb@1,0 {
>                         reg = <0x10000 0 0 0 0>;
>                         resets = <&reset RASPBERRYPI_FIRMWARE_RESET_ID_USB>;
>                 };
> 
> It doesn't warn because the bridge node is also missing 'device_type = 
> "pci";'.
> 
> This is all fairly hard to get right (see recent hikey970 patches for a 
> complex example). I'm thinking about writing a tool that generates a DT 
> with PCI nodes by reading the PCI hierachy from sysfs.

Thanks for the review, I'll fix all those. That tool would be very helpful.

-- 
Nicolás Sáenz