Re: [PATCH v8 4/4] USB: pci-quirks: Add Raspberry Pi 4 quirk

[Nicolas Saenz Julienne]

On Tue, 2020-05-05 at 18:13 +0200, 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
> VideoCore. Inform VideoCore that VL805 was just reset.
> 
> Also, as this creates a dependency between USB_PCI and VideoCore's
> firmware interface, and since USB_PCI can't be set as a module neither
> this can. Reflect that on the firmware interface Kconfg.
> 
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
> ---

It was pointed out to me on the u-boot mailing lists that all this could be
implemented trough a reset controller. In other words have xhci get the reset
controller trough device-tree, assert it, ultamately causing the firmware
routine to be run.

As much as it pains me to go over stuff that's already 'fixed', it seems to me
it's a better solution. On one hand we get over the device-tree dependency mess
(see patch #3), and on the other we transform a pci-quirk into something less
hacky.

That said, before getting my hands dirty, I was wondering if there is any
obvious reasons why I shouldn't do this, note that:

- We're talking here of a PCIe XCHI device, maybe there's an issue integrating
  it with DT, given the fact that, as of today, it's not really represented
  there.

- There is no reset controller support in xhci-pci, maybe there are good
  reasons why. For instance, it's not something that's reflected in any way in
  the spec.

Regards,
Nicolas

> 
> Changes since v5:
>  - Fix Kconfig issue with allmodconfig
> 
> Changes since v4:
>  - Do not split up error message
> 
> Changes since v3:
>  - Add more complete error message
> 
> Changes since v1:
>  - Make RASPBERRYPI_FIRMWARE dependent on this quirk to make sure it
>    gets compiled when needed.
> 
>  drivers/firmware/Kconfig      |  3 ++-
>  drivers/usb/host/pci-quirks.c | 16 ++++++++++++++++
>  2 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
> index 8007d4aa76dc..b42140cff8ac 100644
> --- a/drivers/firmware/Kconfig
> +++ b/drivers/firmware/Kconfig
> @@ -178,8 +178,9 @@ config ISCSI_IBFT
>  	  Otherwise, say N.
>  
>  config RASPBERRYPI_FIRMWARE
> -	tristate "Raspberry Pi Firmware Driver"
> +	bool "Raspberry Pi Firmware Driver"
>  	depends on BCM2835_MBOX
> +	default USB_PCI
>  	help
>  	  This option enables support for communicating with the firmware on the
>  	  Raspberry Pi.
> diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
> index 92150ecdb036..0b949acfa258 100644
> --- a/drivers/usb/host/pci-quirks.c
> +++ b/drivers/usb/host/pci-quirks.c
> @@ -16,6 +16,9 @@
>  #include <linux/export.h>
>  #include <linux/acpi.h>
>  #include <linux/dmi.h>
> +
> +#include <soc/bcm2835/raspberrypi-firmware.h>
> +
>  #include "pci-quirks.h"
>  #include "xhci-ext-caps.h"
>  
> @@ -1243,11 +1246,24 @@ static void quirk_usb_handoff_xhci(struct pci_dev
> *pdev)
>  
>  static void quirk_usb_early_handoff(struct pci_dev *pdev)
>  {
> +	int ret;
> +
>  	/* Skip Netlogic mips SoC's internal PCI USB controller.
>  	 * This device does not need/support EHCI/OHCI handoff
>  	 */
>  	if (pdev->vendor == 0x184e)	/* vendor Netlogic */
>  		return;
> +
> +	if (pdev->vendor == PCI_VENDOR_ID_VIA && pdev->device == 0x3483) {
> +		ret = rpi_firmware_init_vl805(pdev);
> +		if (ret) {
> +			/* Firmware might be outdated, or something failed */
> +			dev_warn(&pdev->dev,
> +				 "Failed to load VL805's firmware: %d. Will
> continue to attempt to work, but bad things might happen. You should fix
> this...\n",
> +				 ret);
> +		}
> +	}
> +
>  	if (pdev->class != PCI_CLASS_SERIAL_USB_UHCI &&
>  			pdev->class != PCI_CLASS_SERIAL_USB_OHCI &&
>  			pdev->class != PCI_CLASS_SERIAL_USB_EHCI &&

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