linux-kernel - Re: [PATCH v2 3/4] PCI: brcmstb: Wait for Raspberry Pi's firmware when present

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Message-ID: <816cccb3-be5d-f0d5-77bd-6afdba3c0848@gmail.com>
Date:   Thu, 20 Feb 2020 10:27:35 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <amurray@...goodpenguin.co.uk>
Cc:     linux-usb@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, gregkh@...uxfoundation.org,
        tim.gover@...pberrypi.org, linux-pci@...r.kernel.org,
        wahrenst@....net, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v2 3/4] PCI: brcmstb: Wait for Raspberry Pi's firmware
 when present



On 2/20/2020 10:14 AM, Nicolas Saenz Julienne wrote:
> On Wed, 2020-02-19 at 11:21 -0800, Florian Fainelli wrote:
>> On 2/19/20 4:39 AM, Nicolas Saenz Julienne wrote:
>>> xHCI's PCI fixup, run at the end of pcie-brcmstb's probe, depends on
>>> RPi4's VideoCore firmware interface to be up and running. It's possible
>>> for both initializations to race, so make sure it's available prior
>>> starting.
>>>
>>> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
>>
>> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
>>
>> It does not look like there is something making sure that
>> CONFIG_RASPBERRYPI_FIRMWARE is being selected or depended on, should we
>> have a "default XHCI_PCI" added to drivers/firmware/Kconfig?
> 
> I think having that would enable the firmware interface for all XHCI_PCI users,
> which isn't ideal. The firmware call has stubs for the case the firmware
> interace isn't compiled, so no problem there. Ultimately we want to enable
> CONFIG_RASPBERRYPI_FIRMWARE only when the built image targets the RPi4
> (reglardless of being arm64/arm32). But I don't think that's feasible.

It would enable the driver, which is only functional if the matching
Device Tree node is present, that seems like a reasonable price to pay
for a multiplatform kernel. After all, this is a functional dependency
for the Pi4.
-- 
Florian