Re: [PATCH v3 10/12] misc: rp1: RaspberryPi RP1 misc driver

[Andrea della Porta <andrea.porta@suse.com>]

Hi Stan,

On 15:43 Mon 04 Nov     , Stanimir Varbanov wrote:
> On 10/28/24 16:07, Andrea della Porta wrote:
> > The RaspberryPi RP1 is a PCI multi function device containing
> > peripherals ranging from Ethernet to USB controller, I2C, SPI
> > and others.
> > 
> > Implement a bare minimum driver to operate the RP1, leveraging
> > actual OF based driver implementations for the on-board peripherals
> > by loading a devicetree overlay during driver probe.
> > 
> > The peripherals are accessed by mapping MMIO registers starting
> > from PCI BAR1 region.
> > 
> > With the overlay approach we can achieve more generic and agnostic
> > approach to managing this chipset, being that it is a PCI endpoint
> > and could possibly be reused in other hw implementations. The
> > presented approach is also used by Bootlin's Microchip LAN966x
> > patchset (see link) as well, for a similar chipset.
> > 
> > Since the gpio line names should be provided by the user, there
> > is an interface through configfs that allows the userspace to
> > load a DT overlay that will provide gpio-line-names property.
> > The interface can be invoked like this:
> > 
> > cat rpi-rp1-gpios-5-b.dtbo > /sys/kernel/config/rp1-cfg/gpio_set_names
> > 
> > and is designed to be similar to what users are already used to
> > from distro with downstream kernel.
> > 
> > For reasons why this driver is contained in drivers/misc, please
> > check the links.
> > 
> > This driver is heavily based on downstream code from RaspberryPi
> > Foundation, and the original author is Phil Elwell.
> > 
> > Link: https://datasheets.raspberrypi.com/rp1/rp1-peripherals.pdf
> > Link: https://lore.kernel.org/all/20240612140208.GC1504919@google.com/
> > Link: https://lore.kernel.org/all/83f7fa09-d0e6-4f36-a27d-cee08979be2a@app.fastmail.com/
> > Link: https://lore.kernel.org/all/2024081356-mutable-everyday-6f9d@gregkh/
> > Link: https://lore.kernel.org/all/20240808154658.247873-1-herve.codina@bootlin.com/
> > 
> > Signed-off-by: Andrea della Porta <andrea.porta@suse.com>
> > ---
> >  MAINTAINERS                   |   1 +
> >  drivers/misc/Kconfig          |   1 +
> >  drivers/misc/Makefile         |   1 +
> >  drivers/misc/rp1/Kconfig      |  21 ++
> >  drivers/misc/rp1/Makefile     |   3 +
> >  drivers/misc/rp1/rp1-pci.dtso |   8 +
> >  drivers/misc/rp1/rp1_pci.c    | 357 ++++++++++++++++++++++++++++++++++
> >  drivers/misc/rp1/rp1_pci.h    |  14 ++
> >  drivers/pci/quirks.c          |   1 +
> >  include/linux/pci_ids.h       |   3 +
> >  10 files changed, 410 insertions(+)
> >  create mode 100644 drivers/misc/rp1/Kconfig
> >  create mode 100644 drivers/misc/rp1/Makefile
> >  create mode 100644 drivers/misc/rp1/rp1-pci.dtso
> >  create mode 100644 drivers/misc/rp1/rp1_pci.c
> >  create mode 100644 drivers/misc/rp1/rp1_pci.h
> > 
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 510a071ede78..032678fb2470 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -19389,6 +19389,7 @@ F:	Documentation/devicetree/bindings/misc/pci1de4,1.yaml
> >  F:	Documentation/devicetree/bindings/pci/pci-ep-bus.yaml
> >  F:	Documentation/devicetree/bindings/pinctrl/raspberrypi,rp1-gpio.yaml
> >  F:	drivers/clk/clk-rp1.c
> > +F:	drivers/misc/rp1/
> >  F:	drivers/pinctrl/pinctrl-rp1.c
> >  F:	include/dt-bindings/clock/rp1.h
> >  F:	include/dt-bindings/misc/rp1.h
> > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > index 3fe7e2a9bd29..ac85cb154100 100644
> > --- a/drivers/misc/Kconfig
> > +++ b/drivers/misc/Kconfig
> > @@ -628,4 +628,5 @@ source "drivers/misc/uacce/Kconfig"
> >  source "drivers/misc/pvpanic/Kconfig"
> >  source "drivers/misc/mchp_pci1xxxx/Kconfig"
> >  source "drivers/misc/keba/Kconfig"
> > +source "drivers/misc/rp1/Kconfig"
> >  endmenu
> > diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> > index a9f94525e181..ae86d69997b4 100644
> > --- a/drivers/misc/Makefile
> > +++ b/drivers/misc/Makefile
> > @@ -72,3 +72,4 @@ obj-$(CONFIG_TPS6594_PFSM)	+= tps6594-pfsm.o
> >  obj-$(CONFIG_NSM)		+= nsm.o
> >  obj-$(CONFIG_MARVELL_CN10K_DPI)	+= mrvl_cn10k_dpi.o
> >  obj-y				+= keba/
> > +obj-$(CONFIG_MISC_RP1)		+= rp1/
> > diff --git a/drivers/misc/rp1/Kconfig b/drivers/misc/rp1/Kconfig
> > new file mode 100644
> > index 000000000000..39c4aa4bf634
> > --- /dev/null
> > +++ b/drivers/misc/rp1/Kconfig
> > @@ -0,0 +1,21 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +#
> > +# RaspberryPi RP1 misc device
> > +#
> > +
> > +config MISC_RP1
> > +        tristate "RaspberryPi RP1 PCIe support"
> > +        depends on OF_IRQ && PCI_MSI && PCI_QUIRKS
> > +        select OF_OVERLAY
> > +        select PCI_DYNAMIC_OF_NODES
> > +        help
> > +          Support the RP1 peripheral chip found on Raspberry Pi 5 board.
> > +
> > +          This device supports several sub-devices including e.g. Ethernet
> > +	  controller, USB controller, I2C, SPI and UART.
> > +
> > +          The driver is responsible for enabling the DT node once the PCIe
> > +	  endpoint has been configured, and handling interrupts.
> > +
> > +          This driver uses an overlay to load other drivers to support for
> > +	  RP1 internal sub-devices.
> > diff --git a/drivers/misc/rp1/Makefile b/drivers/misc/rp1/Makefile
> > new file mode 100644
> > index 000000000000..508b4cb05627
> > --- /dev/null
> > +++ b/drivers/misc/rp1/Makefile
> > @@ -0,0 +1,3 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +obj-$(CONFIG_MISC_RP1)		+= rp1-pci.o
> > +rp1-pci-objs			:= rp1_pci.o rp1-pci.dtbo.o
> > diff --git a/drivers/misc/rp1/rp1-pci.dtso b/drivers/misc/rp1/rp1-pci.dtso
> > new file mode 100644
> > index 000000000000..0bf2f4bb18e6
> > --- /dev/null
> > +++ b/drivers/misc/rp1/rp1-pci.dtso
> > @@ -0,0 +1,8 @@
> > +// SPDX-License-Identifier: (GPL-2.0 OR MIT)
> > +
> > +/* the dts overlay is included from the dts directory so
> > + * it can be possible to check it with CHECK_DTBS while
> > + * also compile it from the driver source directory.
> > + */
> > +
> > +#include "arm64/broadcom/rp1.dtso"
> > diff --git a/drivers/misc/rp1/rp1_pci.c b/drivers/misc/rp1/rp1_pci.c
> > new file mode 100644
> > index 000000000000..30d7a15dc7f1
> > --- /dev/null
> > +++ b/drivers/misc/rp1/rp1_pci.c
> > @@ -0,0 +1,357 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (c) 2018-24 Raspberry Pi Ltd.
> > + * All rights reserved.
> > + */
> > +
> > +#include <linux/err.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/irq.h>
> > +#include <linux/irqchip/chained_irq.h>
> > +#include <linux/irqdomain.h>
> > +#include <linux/module.h>
> > +#include <linux/msi.h>
> > +#include <linux/of_platform.h>
> > +#include <linux/pci.h>
> > +#include <linux/platform_device.h>
> > +
> > +#include "rp1_pci.h"
> > +
> > +#define RP1_DRIVER_NAME		"rp1"
> > +
> > +#define RP1_HW_IRQ_MASK		GENMASK(5, 0)
> > +
> > +#define REG_SET			0x800
> > +#define REG_CLR			0xc00
> > +
> > +/* MSI-X CFG registers start at 0x8 */
> > +#define MSIX_CFG(x) (0x8 + (4 * (x)))
> > +
> > +#define MSIX_CFG_IACK_EN        BIT(3)
> > +#define MSIX_CFG_IACK           BIT(2)
> > +#define MSIX_CFG_ENABLE         BIT(0)
> > +
> > +/* Address map */
> > +#define RP1_PCIE_APBS_BASE	0x108000
> > +
> > +/* Interrupts */
> > +#define RP1_INT_IO_BANK0	0
> > +#define RP1_INT_IO_BANK1	1
> > +#define RP1_INT_IO_BANK2	2
> > +#define RP1_INT_AUDIO_IN	3
> > +#define RP1_INT_AUDIO_OUT	4
> > +#define RP1_INT_PWM0		5
> > +#define RP1_INT_ETH		6
> > +#define RP1_INT_I2C0		7
> > +#define RP1_INT_I2C1		8
> > +#define RP1_INT_I2C2		9
> > +#define RP1_INT_I2C3		10
> > +#define RP1_INT_I2C4		11
> > +#define RP1_INT_I2C5		12
> > +#define RP1_INT_I2C6		13
> > +#define RP1_INT_I2S0		14
> > +#define RP1_INT_I2S1		15
> > +#define RP1_INT_I2S2		16
> > +#define RP1_INT_SDIO0		17
> > +#define RP1_INT_SDIO1		18
> > +#define RP1_INT_SPI0		19
> > +#define RP1_INT_SPI1		20
> > +#define RP1_INT_SPI2		21
> > +#define RP1_INT_SPI3		22
> > +#define RP1_INT_SPI4		23
> > +#define RP1_INT_SPI5		24
> > +#define RP1_INT_UART0		25
> > +#define RP1_INT_TIMER_0		26
> > +#define RP1_INT_TIMER_1		27
> > +#define RP1_INT_TIMER_2		28
> > +#define RP1_INT_TIMER_3		29
> > +#define RP1_INT_USBHOST0	30
> > +#define RP1_INT_USBHOST0_0	31
> > +#define RP1_INT_USBHOST0_1	32
> > +#define RP1_INT_USBHOST0_2	33
> > +#define RP1_INT_USBHOST0_3	34
> > +#define RP1_INT_USBHOST1	35
> > +#define RP1_INT_USBHOST1_0	36
> > +#define RP1_INT_USBHOST1_1	37
> > +#define RP1_INT_USBHOST1_2	38
> > +#define RP1_INT_USBHOST1_3	39
> > +#define RP1_INT_DMA		40
> > +#define RP1_INT_PWM1		41
> > +#define RP1_INT_UART1		42
> > +#define RP1_INT_UART2		43
> > +#define RP1_INT_UART3		44
> > +#define RP1_INT_UART4		45
> > +#define RP1_INT_UART5		46
> > +#define RP1_INT_MIPI0		47
> > +#define RP1_INT_MIPI1		48
> > +#define RP1_INT_VIDEO_OUT	49
> > +#define RP1_INT_PIO_0		50
> > +#define RP1_INT_PIO_1		51
> > +#define RP1_INT_ADC_FIFO	52
> > +#define RP1_INT_PCIE_OUT	53
> > +#define RP1_INT_SPI6		54
> > +#define RP1_INT_SPI7		55
> > +#define RP1_INT_SPI8		56
> > +#define RP1_INT_SYSCFG		58
> > +#define RP1_INT_CLOCKS_DEFAULT	59
> > +#define RP1_INT_VBUSCTRL	60
> > +#define RP1_INT_PROC_MISC	57
> > +#define RP1_INT_END		61
> > +
> 
> How those interrupts are supposed to be used by rp1-pci.dtso (or from
> rp1.dtso)?

Unfortunately they will not. See below.

> 
> include/dt-bindings/interrupt-controller/raspberrypi,rp1-interrupts.h ?

Please see:
https://lore.kernel.org/all/e05705c1-95dc-4d77-8a0d-8c2a785b0b05@kernel.org/

> 
> > +struct rp1_dev {
> > +	struct pci_dev *pdev;
> > +	struct device *dev;
> > +	struct irq_domain *domain;
> > +	struct irq_data *pcie_irqds[64];
> > +	void __iomem *bar1;
> > +	int ovcs_id;
> > +	bool level_triggered_irq[RP1_INT_END];
> > +};
> > +
> > +static void msix_cfg_set(struct rp1_dev *rp1, unsigned int hwirq, u32 value)
> > +{
> > +	iowrite32(value, rp1->bar1 + RP1_PCIE_APBS_BASE + REG_SET + MSIX_CFG(hwirq));
> > +}
> > +
> > +static void msix_cfg_clr(struct rp1_dev *rp1, unsigned int hwirq, u32 value)
> > +{
> > +	iowrite32(value, rp1->bar1 + RP1_PCIE_APBS_BASE + REG_CLR + MSIX_CFG(hwirq));
> > +}
> > +
> > +static void rp1_mask_irq(struct irq_data *irqd)
> > +{
> > +	struct rp1_dev *rp1 = irqd->domain->host_data;
> > +	struct irq_data *pcie_irqd = rp1->pcie_irqds[irqd->hwirq];
> > +
> > +	pci_msi_mask_irq(pcie_irqd);
> > +}
> > +
> > +static void rp1_unmask_irq(struct irq_data *irqd)
> > +{
> > +	struct rp1_dev *rp1 = irqd->domain->host_data;
> > +	struct irq_data *pcie_irqd = rp1->pcie_irqds[irqd->hwirq];
> > +
> > +	pci_msi_unmask_irq(pcie_irqd);
> > +}
> > +
> > +static int rp1_irq_set_type(struct irq_data *irqd, unsigned int type)
> > +{
> > +	struct rp1_dev *rp1 = irqd->domain->host_data;
> > +	unsigned int hwirq = (unsigned int)irqd->hwirq;
> > +
> > +	switch (type) {
> > +	case IRQ_TYPE_LEVEL_HIGH:
> > +		dev_dbg(rp1->dev, "MSIX IACK EN for irq %d\n", hwirq);
> > +		msix_cfg_set(rp1, hwirq, MSIX_CFG_IACK_EN);
> > +		rp1->level_triggered_irq[hwirq] = true;
> > +	break;
> > +	case IRQ_TYPE_EDGE_RISING:
> > +		msix_cfg_clr(rp1, hwirq, MSIX_CFG_IACK_EN);
> > +		rp1->level_triggered_irq[hwirq] = false;
> > +		break;
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static struct irq_chip rp1_irq_chip = {
> > +	.name            = "rp1_irq_chip",
> 
> tabs instead of spaces here and below.

Ack.

> 
> > +	.irq_mask        = rp1_mask_irq,
> > +	.irq_unmask      = rp1_unmask_irq,
> > +	.irq_set_type    = rp1_irq_set_type,
> > +};
> > +
> > +static void rp1_chained_handle_irq(struct irq_desc *desc)
> > +{
> > +	unsigned int hwirq = desc->irq_data.hwirq & RP1_HW_IRQ_MASK;
> > +	struct rp1_dev *rp1 = irq_desc_get_handler_data(desc);
> > +	struct irq_chip *chip = irq_desc_get_chip(desc);
> > +	int virq;
> 
> unsigned int

Ack.

> 
> > +
> > +	chained_irq_enter(chip, desc);
> > +
> > +	virq = irq_find_mapping(rp1->domain, hwirq);
> > +	generic_handle_irq(virq);
> > +	if (rp1->level_triggered_irq[hwirq])
> > +		msix_cfg_set(rp1, hwirq, MSIX_CFG_IACK);
> > +
> > +	chained_irq_exit(chip, desc);
> > +}
> > +
> > +static int rp1_irq_xlate(struct irq_domain *d, struct device_node *node,
> > +			 const u32 *intspec, unsigned int intsize,
> > +			 unsigned long *out_hwirq, unsigned int *out_type)
> > +{
> > +	struct rp1_dev *rp1 = d->host_data;
> > +	struct irq_data *pcie_irqd;
> > +	unsigned long hwirq;
> > +	int pcie_irq;
> > +	int ret;
> > +
> > +	ret = irq_domain_xlate_twocell(d, node, intspec, intsize,
> > +				       &hwirq, out_type);
> > +	if (ret)
> > +		return ret;
> > +
> > +	pcie_irq = pci_irq_vector(rp1->pdev, hwirq);
> > +	pcie_irqd = irq_get_irq_data(pcie_irq);
> > +	rp1->pcie_irqds[hwirq] = pcie_irqd;
> > +	*out_hwirq = hwirq;
> > +
> > +	return 0;
> > +}
> > +
> > +static int rp1_irq_activate(struct irq_domain *d, struct irq_data *irqd,
> > +			    bool reserve)
> > +{
> > +	struct rp1_dev *rp1 = d->host_data;
> > +
> > +	msix_cfg_set(rp1, (unsigned int)irqd->hwirq, MSIX_CFG_ENABLE);
> > +
> > +	return 0;
> > +}
> > +
> > +static void rp1_irq_deactivate(struct irq_domain *d, struct irq_data *irqd)
> > +{
> > +	struct rp1_dev *rp1 = d->host_data;
> > +
> > +	msix_cfg_clr(rp1, (unsigned int)irqd->hwirq, MSIX_CFG_ENABLE);
> > +}
> > +
> > +static const struct irq_domain_ops rp1_domain_ops = {
> > +	.xlate      = rp1_irq_xlate,
> > +	.activate   = rp1_irq_activate,
> > +	.deactivate = rp1_irq_deactivate,
> > +};
> > +
> > +static void rp1_unregister_interrupts(struct pci_dev *pdev)
> > +{
> > +	struct rp1_dev *rp1 = pci_get_drvdata(pdev);
> > +	int irq, i;
> > +
> > +	for (i = 0; i < RP1_INT_END; i++) {
> > +		irq = irq_find_mapping(rp1->domain, i);
> > +		irq_dispose_mapping(irq);
> > +	}
> 
> new line

Ack.

> 
> > +	irq_domain_remove(rp1->domain);
> > +	pci_free_irq_vectors(pdev);
> > +}
> > +
> > +static int rp1_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> > +{
> > +	u32 dtbo_size = __dtbo_rp1_pci_end - __dtbo_rp1_pci_begin;
> > +	void *dtbo_start = __dtbo_rp1_pci_begin;
> > +	struct device *dev = &pdev->dev;
> > +	struct device_node *rp1_node;
> > +	struct rp1_dev *rp1;
> > +	int err  = 0;
> > +	int i;
> > +
> > +	rp1_node = dev_of_node(dev);
> > +	if (!rp1_node) {
> > +		dev_err(dev, "Missing of_node for device\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	rp1 = devm_kzalloc(&pdev->dev, sizeof(*rp1), GFP_KERNEL);
> > +	if (!rp1)
> > +		return -ENOMEM;
> > +
> > +	rp1->pdev = pdev;
> > +	rp1->dev = &pdev->dev;
> 
> rp1->dev is used only once in dev_dbg macro. You could drop it and
> extract struct device from rp1->pdev.

Good catch, thanks!

> 
> > +
> > +	if (pci_resource_len(pdev, 1) <= 0x10000) {
> > +		dev_err(&pdev->dev,
> > +			"Not initialised - is the firmware running?\n");
> 
> no need of a new line

It goes past 80 columns, no?

> 
> > +		return -EINVAL;
> > +	}
> > +
> > +	err = pcim_enable_device(pdev);
> > +	if (err < 0) {
> > +		dev_err(&pdev->dev, "Enabling PCI device has failed: %d",
> > +			err);
> 
> ditto

Ditto.

> 
> > +		return err;
> > +	}
> > +
> > +	rp1->bar1 = pcim_iomap(pdev, 1, 0);
> > +	if (!rp1->bar1) {
> > +		dev_err(&pdev->dev, "Cannot map PCI BAR\n");
> > +		return -EIO;
> > +	}
> > +
> > +	pci_set_master(pdev);
> > +
> > +	err = pci_alloc_irq_vectors(pdev, RP1_INT_END, RP1_INT_END,
> > +				    PCI_IRQ_MSIX);
> 
> ditto

Ditto.

> 
> > +	if (err != RP1_INT_END) {
> 
> an 'err' could be smaller then RP1_INT_END but still positive, thus
> .probe will return positive error code.

Ack.

> 
> > +		dev_err(&pdev->dev, "pci_alloc_irq_vectors failed - %d\n", err);
> > +		return err;
> > +	}
> > +
> > +	pci_set_drvdata(pdev, rp1);
> > +	rp1->domain = irq_domain_add_linear(rp1_node, RP1_INT_END,
> > +					    &rp1_domain_ops, rp1);
> 
> irq_domain_add_linear() could fail, check for error ...

Ack.

> 
> > +
> > +	for (i = 0; i < RP1_INT_END; i++) {
> > +		int irq = irq_create_mapping(rp1->domain, i);
> 
> irq_create_mapping() returns 'unsigned int', maybe something like this:
> 
> 		unsigned int irq = irq_create_mapping(rp1->domain, i);
> 		if (!irq) {
> 			err = -EINVAL; (or -ENOMEM)
> 			...
> 		}

Right, thanks.

> 
> > +
> > +		if (irq < 0) {
> > +			dev_err(&pdev->dev, "failed to create irq mapping\n");
> > +			err = irq;
> > +			goto err_unload_overlay;
> 
> 			goto err_unregister_interrupts; ?

Ack.

> 
> > +		}
> 
> new line, please

Ack.

> 
> > +		irq_set_chip_and_handler(irq, &rp1_irq_chip, handle_level_irq);
> > +		irq_set_probe(irq);
> > +		irq_set_chained_handler_and_data(pci_irq_vector(pdev, i),
> > +						 rp1_chained_handle_irq, rp1);
> > +	}
> > +
> > +	err = of_overlay_fdt_apply(dtbo_start, dtbo_size, &rp1->ovcs_id, rp1_node);
> > +	if (err)
> > +		goto err_unregister_interrupts;
> > +
> > +	err = of_platform_default_populate(rp1_node, NULL, dev);
> > +	if (err)
> > +		goto err_unload_overlay;
> > +
> > +	return 0;
> > +
> > +err_unload_overlay:
> > +	of_overlay_remove(&rp1->ovcs_id);
> > +err_unregister_interrupts:
> > +	rp1_unregister_interrupts(pdev);
> > +
> > +	return err;
> > +}
> > +
> > +static void rp1_remove(struct pci_dev *pdev)
> > +{
> > +	struct rp1_dev *rp1 = pci_get_drvdata(pdev);
> > +	struct device *dev = &pdev->dev;
> > +
> > +	of_platform_depopulate(dev);
> > +	of_overlay_remove(&rp1->ovcs_id);
> > +	rp1_unregister_interrupts(pdev);
> > +}
> > +
> > +static const struct pci_device_id dev_id_table[] = {
> > +	{ PCI_DEVICE(PCI_VENDOR_ID_RPI, PCI_DEVICE_ID_RPI_RP1_C0), },
> > +	{ 0, }
> > +};
> > +MODULE_DEVICE_TABLE(pci, dev_id_table);
> > +
> > +static struct pci_driver rp1_driver = {
> > +	.name		= RP1_DRIVER_NAME,
> > +	.id_table	= dev_id_table,
> > +	.probe		= rp1_probe,
> > +	.remove		= rp1_remove,
> > +};
> > +
> > +module_pci_driver(rp1_driver);
> > +
> > +MODULE_AUTHOR("Phil Elwell <phil@raspberrypi.com>");
> > +MODULE_AUTHOR("Andrea della Porta <andrea.porta@suse.com>");
> > +MODULE_DESCRIPTION("RP1 wrapper");
> > +MODULE_LICENSE("GPL");
> > diff --git a/drivers/misc/rp1/rp1_pci.h b/drivers/misc/rp1/rp1_pci.h
> > new file mode 100644
> > index 000000000000..7982f13bad9b
> > --- /dev/null
> > +++ b/drivers/misc/rp1/rp1_pci.h
> > @@ -0,0 +1,14 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +
> > +/*
> > + * Copyright (c) 2018-24 Raspberry Pi Ltd.
> > + * All rights reserved.
> > + */
> > +
> > +#ifndef _RP1_EXTERN_H_
> > +#define _RP1_EXTERN_H_
> > +
> > +extern char __dtbo_rp1_pci_begin[];
> > +extern char __dtbo_rp1_pci_end[];
> 
> Could you point me where those two variables are used outside of rp1_pci.c?

Nowhere else. For the rationale behind this please see:
https://lore.kernel.org/all/e6e6c230-370f-4b04-8cb7-4158dd51efdc@lunn.ch/
and followups.

Many thanks,
Andrea


> 
> ~Stan
>