Re: [PATCH v6 2/4] firmware: raspberrypi: Introduce vl805 init routine

[Nicolas Saenz Julienne]

Hi Bjorn,
thanks for taking time with this.

On Wed, 2020-04-01 at 15:37 -0500, Bjorn Helgaas wrote:
> On Tue, Mar 24, 2020 at 07:28:10PM +0100, Nicolas Saenz Julienne wrote:
> > On the Raspberry Pi 4, after a PCI reset, VL805's firmware may either be
> > loaded directly from an EEPROM or, if not present, by the SoC's
> > VideCore. The function informs VideCore that VL805 was just reset, or
> > requests for a probe defer.
> 
> Cover letter mentions both "VideCore" and "VideoCore".  I dunno which
> is correct, but between the commit log and the comment, this patch
> mentions "VideCore" four times.

Ouch, sorry, it's VideoCore. I have an auto complete thing, wrote it once wrong
and polluted the whole patch.

> > Based on Tim Gover's downstream implementation.
> 
> Maybe a URL?

I was under the impression that adding links in the commit log that are likely
to be short-lived was frowned upon. That said I could've added it into the
cover letter. For reference here it is:

https://github.com/raspberrypi/linux/commit/9935b4c7e360b4494b4cb6e3ce797238a1ab78bd

> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
> > Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> > 
> > ---
> > Changes since v4:
> >  - Inline function definition when RASPBERRYPI_FIRMWARE is not defined
> > 
> > Changes since v1:
> >  - Move include into .c file and add forward declaration to .h
> > 
> >  drivers/firmware/raspberrypi.c             | 38 ++++++++++++++++++++++
> >  include/soc/bcm2835/raspberrypi-firmware.h |  7 ++++
> >  2 files changed, 45 insertions(+)
> > 
> > diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
> > index da26a584dca0..cbb495aff6a0 100644
> > --- a/drivers/firmware/raspberrypi.c
> > +++ b/drivers/firmware/raspberrypi.c
> > @@ -12,6 +12,7 @@
> >  #include <linux/of_platform.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/slab.h>
> > +#include <linux/pci.h>
> >  #include <soc/bcm2835/raspberrypi-firmware.h>
> >  
> >  #define MBOX_MSG(chan, data28)		(((data28) & ~0xf) | ((chan) &
> > 0xf))
> > @@ -286,6 +287,43 @@ struct rpi_firmware *rpi_firmware_get(struct
> > device_node *firmware_node)
> >  }
> >  EXPORT_SYMBOL_GPL(rpi_firmware_get);
> >  
> > +/*
> > + * On the Raspberry Pi 4, after a PCI reset, VL805's firmware may either be
> > + * loaded directly from an EEPROM or, if not present, by the SoC's
> > VideCore.
> > + * Inform VideCore that VL805 was just reset, or defer xhci's probe if not
> > yet
> > + * joinable trough the mailbox interface.
> 
> s/trough/through/

Noted.

> I don't see anything in this patch that looks like a mailbox
> interface, but maybe that's just because I don't know anything about
> Raspberry Pi.

There are two layers to this. The bcm2835-mailbox interface, that is generic to
all SoC users and the Raspberry Pi firmware driver, which interacts with RPi's
custom VideoCore firmware trough the bcm2835-mailbox, and provides a light
level of abstraction. It's like that to keep a clear separation between what's
a SoC feature an what is RPi specific.

So with a call to rpi_firmware_get() you're supposed to get a handle to the
shared RPi firmware structure. As long as it's ready. To pass messages down the
mailbox, you call rpi_firmware_property(), which takes care of contention,
formating and DMA issues, before passing it into the actual mailbox interface
and beyond.

> > + */
> > +int rpi_firmware_init_vl805(struct pci_dev *pdev)
> > +{
> > +	struct device_node *fw_np;
> > +	struct rpi_firmware *fw;
> > +	u32 dev_addr;
> > +	int ret;
> > +
> > +	fw_np = of_find_compatible_node(NULL, NULL,
> > +					"raspberrypi,bcm2835-firmware");
> > +	if (!fw_np)
> > +		return 0;
> > +
> > +	fw = rpi_firmware_get(fw_np);
> > +	of_node_put(fw_np);
> > +	if (!fw)
> > +		return -EPROBE_DEFER;
> > +
> > +	dev_addr = pdev->bus->number << 20 | PCI_SLOT(pdev->devfn) << 15 |
> > +		   PCI_FUNC(pdev->devfn) << 12;
> > +
> > +	ret = rpi_firmware_property(fw, RPI_FIRMWARE_NOTIFY_XHCI_RESET,
> > +				    &dev_addr, sizeof(dev_addr));
> > +	if (ret)
> > +		return ret;
> > +
> > +	dev_dbg(&pdev->dev, "loaded Raspberry Pi's VL805 firmware\n");
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(rpi_firmware_init_vl805);
> > +
> >  static const struct of_device_id rpi_firmware_of_match[] = {
> >  	{ .compatible = "raspberrypi,bcm2835-firmware", },
> >  	{},

[...]

Regards,
Nicolas

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