From: Nicolas Saenz Julienne <firstname.lastname@example.org>
To: Bjorn Helgaas <email@example.com>
Florian Fainelli <firstname.lastname@example.org>,
Lorenzo Pieralisi <email@example.com>,
Andrew Murray <firstname.lastname@example.org>,
Rob Herring <email@example.com>
Subject: Re: [PATCH v6 3/4] PCI: brcmstb: Wait for Raspberry Pi's firmware when present
Date: Sat, 04 Apr 2020 21:20:27 +0200 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
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On Thu, 2020-04-02 at 14:38 -0500, Bjorn Helgaas wrote:
> [+cc Rob for DT platform device dependency question]
> On Thu, Apr 02, 2020 at 04:27:23PM +0200, Nicolas Saenz Julienne wrote:
> > Sorry it wasn't clear enough, I'll redo this comment. Also note that
> > the PCIe bus and the XHCI chip are hardwired, so that's the only
> > device that'll ever be available on the bus.
> > VIA805's XHCI firmware has to be loaded trough RPi's firmware
> > mailbox in between the PCIe bus probe and the subsequent USB probe.
> > Note that a PCI reset clears the firmware. The only mechanism
> > available in between the two operations are PCI Fixups. These are
> > limited in their own way, as I can't return -EPROBE_DEFER if the
> > firmware interface isn't available yet. Hence the need for an
> > explicit dependency between pcie-brcmstb and raspberrypi's firmware
> > mailbox device.
> > Your concern here showcases this series' limitations. From a high
> > level perspective it's not clear to me who should be responsible for
> > downloading the firmware.
> I think it's fairly common for drivers to download firmware to their
> devices. I guess there's not really any need to download the firmware
> until a driver wants to use the device, right?
> > And I get the feeling I'm abusing PCI fixups. I haven't found any
> > smart way to deal with this three way dependency of
> > platform/non-platform devices.
> So IIUC, the three-way dependency involves:
> 1) brcm_pcie_probe(), which initialize the PCI host controller
> platform device, enumerates PCI devices, and makes them available
> for driver binding,
Yes, and also resets the PCI bus, which will clear VL805's firmware (the XHCI
> 2) the firmware mailbox initialization (maybe
> 3) quirk_usb_early_handoff(), which downloads firmware to the VL805
> PCI USB adapter via rpi_firmware_init_vl805(), which uses the
> firmware mailbox?
And yes, that's the general idea.
> Is there some way to express a dependency between
> "raspberrypi,bcm2835-firmware" (the platform device claimed by
> rpi_firmware_probe() and "brcm,bcm2711-pcie"? If we could ensure that
> rpi_firmware_probe() runs before brcm_pcie_probe(), would that solve
> part of this?
That's ultimately what this patch tries to achieve. If there was a way to
offload it to DT it would be way nicer.
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next prev parent reply other threads:[~2020-04-04 19:20 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-24 18:28 [PATCH v6 0/4] USB: pci-quirks: Add Raspberry Pi 4 quirk Nicolas Saenz Julienne
2020-03-24 18:28 ` [PATCH v6 1/4] soc: bcm2835: Sync xHCI reset firmware property with downstream Nicolas Saenz Julienne
2020-04-02 18:01 ` Bjorn Helgaas
2020-04-04 20:11 ` Florian Fainelli
2020-03-24 18:28 ` [PATCH v6 2/4] firmware: raspberrypi: Introduce vl805 init routine Nicolas Saenz Julienne
2020-04-01 20:37 ` Bjorn Helgaas
2020-04-02 11:32 ` Nicolas Saenz Julienne
2020-04-02 19:40 ` Bjorn Helgaas
2020-04-04 18:56 ` Nicolas Saenz Julienne
2020-03-24 18:28 ` [PATCH v6 3/4] PCI: brcmstb: Wait for Raspberry Pi's firmware when present Nicolas Saenz Julienne
2020-04-01 20:41 ` Bjorn Helgaas
2020-04-02 14:27 ` Nicolas Saenz Julienne
2020-04-02 19:38 ` Bjorn Helgaas
2020-04-04 19:20 ` Nicolas Saenz Julienne [this message]
2020-04-04 20:09 ` Florian Fainelli
2020-03-24 18:28 ` [PATCH v6 4/4] USB: pci-quirks: Add Raspberry Pi 4 quirk Nicolas Saenz Julienne
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