archive mirror
 help / color / mirror / Atom feed
From: Florian Fainelli <>
To: Nicolas Saenz Julienne <>,
	Bjorn Helgaas <>
	Florian Fainelli <>,,
	Lorenzo Pieralisi <>,
	Andrew Murray <>,,,,,,,,,
	Rob Herring <>
Subject: Re: [PATCH v6 3/4] PCI: brcmstb: Wait for Raspberry Pi's firmware when present
Date: Sat, 4 Apr 2020 13:09:56 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 4/4/2020 12:20 PM, Nicolas Saenz Julienne wrote:
> 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
> chip).
>>   2) the firmware mailbox initialization (maybe
>>   rpi_firmware_probe()?),
>>   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.

Have you looked whether device links between producer/consumer could
help here? AFAICT there is not usually a way to express an ordering
dependency other than by referencing symbols from a different module,
which falls apart when everything gets built into the kernel obviously
and then you are at the mercy of the linking order and initicall levels.

  reply	other threads:[~2020-04-04 20:10 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
2020-04-04 20:09           ` Florian Fainelli [this message]
2020-03-24 18:28 ` [PATCH v6 4/4] USB: pci-quirks: Add Raspberry Pi 4 quirk Nicolas Saenz Julienne

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).