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Date:   Sat, 2 May 2020 11:05:12 +0200
From:   Stefan Wahren <wahrenst@....net>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        f.fainelli@...il.com, gregkh@...uxfoundation.org,
        helgaas@...nel.org, linux-kernel@...r.kernel.org,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com
Cc:     linux-usb@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, tim.gover@...pberrypi.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v7 2/4] firmware: raspberrypi: Introduce vl805 init
 routine

Hi Nicolas,

Am 29.04.20 um 18:47 schrieb Nicolas Saenz Julienne:
> The Raspberry Pi 4 gets its USB functionality from VL805, a PCIe chip
> that implements xHCI. After a PCI reset, VL805's firmware may either be
> loaded directly from an EEPROM or, if not present, by the SoC's
> co-processor, VideoCore. RPi4's VideoCore OS contains both the non public
> firmware load logic and the VL805 firmware blob. The function this patch
> introduces triggers the aforementioned process.
>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
>
> ---
>
> Change since v6:
> - Add test to avoid loading the firmware when not needed
> - Since we have it around, print VL805's firmware version, it'll make
> debugging easier in the future
> - Correct typos
> - Add a clearer view of HW topology in patch description
>
> 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             | 52 ++++++++++++++++++++++
>  include/soc/bcm2835/raspberrypi-firmware.h |  7 +++
>  2 files changed, 59 insertions(+)
>
> diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
> index da26a584dca0..230c05e53403 100644
> --- a/drivers/firmware/raspberrypi.c
> +++ b/drivers/firmware/raspberrypi.c
> @@ -12,6 +12,8 @@
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
>  #include <linux/slab.h>
> +#include <linux/pci.h>
> +#include <linux/delay.h>
>  #include <soc/bcm2835/raspberrypi-firmware.h>
>
>  #define MBOX_MSG(chan, data28)		(((data28) & ~0xf) | ((chan) & 0xf))
> @@ -19,6 +21,8 @@
>  #define MBOX_DATA28(msg)		((msg) & ~0xf)
>  #define MBOX_CHAN_PROPERTY		8
>
> +#define VL805_PCI_CONFIG_VERSION_OFFSET		0x50
> +
>  static struct platform_device *rpi_hwmon;
>  static struct platform_device *rpi_clk;
>
> @@ -286,6 +290,54 @@ struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node)
>  }
>  EXPORT_SYMBOL_GPL(rpi_firmware_get);
>
> +/*
> + * The Raspberry Pi 4 gets its USB functionality from VL805, a PCIe chip that
> + * implements xHCI. After a PCI reset, VL805's firmware may either be loaded
> + * directly from an EEPROM or, if not present, by the SoC's co-processor,
> + * VideoCore. RPi4's VideoCore OS contains both the non public firmware load
> + * logic and the VL805 firmware blob. This function triggers the aforementioned
> + * process.
> + */
> +int rpi_firmware_init_vl805(struct pci_dev *pdev)
> +{
> +	struct device_node *fw_np;
> +	struct rpi_firmware *fw;
> +	u32 dev_addr, version;
> +	int ret = 0;
> +
> +	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 -ENODEV;
> +
> +	/* Make sure we don't trigger a firmware load unnecesarely *
s/unnecesarely/unnecessarily/
> +	pci_read_config_dword(pdev, VL805_PCI_CONFIG_VERSION_OFFSET, &version);
pci_read_config_dword() can fail, we might want to store the return value?
> +	if (version)
> +		goto exit;
> +
> +	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));
> +	/* Wait for vl805 to startup */
> +	udelay(200);

I know, it makes it harder to read but do we really want to wait
unnecessarily if rpi_firmware_property failed?

Btw i assume we are in non-atomic context, so maybe it's worth to use
usleep_range() here?

> +
> +exit:
> +	if (!version)
> +		pci_read_config_dword(pdev, VL805_PCI_CONFIG_VERSION_OFFSET,
> +				      &version);
> +	pci_info(pdev, "VL805 firmware version %08x\n", version);

In case pci_read_config_dword() fails the return code would be more helpful.

Best regards

> +	return ret;
> +
> +}
> +EXPORT_SYMBOL_GPL(rpi_firmware_init_vl805);
> +
>  static const struct of_device_id rpi_firmware_of_match[] = {
>  	{ .compatible = "raspberrypi,bcm2835-firmware", },
>  	{},
> diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
> index cc9cdbc66403..3025aca3c358 100644
> --- a/include/soc/bcm2835/raspberrypi-firmware.h
> +++ b/include/soc/bcm2835/raspberrypi-firmware.h
> @@ -10,6 +10,7 @@
>  #include <linux/of_device.h>
>
>  struct rpi_firmware;
> +struct pci_dev;
>
>  enum rpi_firmware_property_status {
>  	RPI_FIRMWARE_STATUS_REQUEST = 0,
> @@ -141,6 +142,7 @@ int rpi_firmware_property(struct rpi_firmware *fw,
>  int rpi_firmware_property_list(struct rpi_firmware *fw,
>  			       void *data, size_t tag_size);
>  struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node);
> +int rpi_firmware_init_vl805(struct pci_dev *pdev);
>  #else
>  static inline int rpi_firmware_property(struct rpi_firmware *fw, u32 tag,
>  					void *data, size_t len)
> @@ -158,6 +160,11 @@ static inline struct rpi_firmware *rpi_firmware_get(struct device_node *firmware
>  {
>  	return NULL;
>  }
> +
> +static inline int rpi_firmware_init_vl805(struct pci_dev *pdev)
> +{
> +	return 0;
> +}
>  #endif
>
>  #endif /* __SOC_RASPBERRY_FIRMWARE_H__ */

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