linux-kernel - Re: [PATCH v5 08/10] misc: rp1: RaspberryPi RP1 misc driver

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Message-ID: <Z2A0aAPotT0NvoCl@apocalypse>
Date: Mon, 16 Dec 2024 15:08:40 +0100
From: Andrea della Porta <andrea.porta@...e.com>
To: Rob Herring <robh@...nel.org>
Cc: Andrea della Porta <andrea.porta@...e.com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczynski <kw@...ux.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Bartosz Golaszewski <brgl@...ev.pl>,
	Derek Kiernan <derek.kiernan@....com>,
	Dragan Cvetic <dragan.cvetic@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Saravana Kannan <saravanak@...gle.com>, linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-gpio@...r.kernel.org,
	Masahiro Yamada <masahiroy@...nel.org>,
	Stefan Wahren <wahrenst@....net>,
	Herve Codina <herve.codina@...tlin.com>,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH v5 08/10] misc: rp1: RaspberryPi RP1 misc driver

Hi Rob,

On 16:48 Tue 10 Dec     , Rob Herring wrote:
> On Mon, Dec 02, 2024 at 12:19:32PM +0100, 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
> 
> Where's the configfs support? This looks like a stale comment.

Yes, you are right. Thanks for pointing that out, I've dropped that
paragraph, since there is no gpio name support in this specific patchset
anymore.

> 
> If this is the general purpose configfs interface for overlays, that's 
> likely never going upstream. If you want this support, then you should 
> load your overlay with the firmware loader instead of building it into 
> the kernel. You can of course add that later.

I think the best thing would be to leave the actual base overlay compiled
inside the driver as it is now, and to prepare a secondary overlay for the
gpio names to be loaded as a binary blob through request_firmware(). Does
it make sense? Of course, the gpio name overlay support would be a future
patchset of its own.

> 
> > 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@...e.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    | 366 ++++++++++++++++++++++++++++++++++
> >  drivers/misc/rp1/rp1_pci.h    |  14 ++
> >  drivers/pci/quirks.c          |   1 +
> >  include/linux/pci_ids.h       |   3 +
> >  10 files changed, 419 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 fbdd8594aa7e..d67ba6d10aa8 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -19583,6 +19583,7 @@ 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 09cbe3f0ab1e..ffa4d8315c35 100644
> > --- a/drivers/misc/Kconfig
> > +++ b/drivers/misc/Kconfig
> > @@ -651,4 +651,5 @@ 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 40bf953185c7..3b6b07a23aac 100644
> > --- a/drivers/misc/Makefile
> > +++ b/drivers/misc/Makefile
> > @@ -74,3 +74,4 @@ lan966x-pci-objs		:= lan966x_pci.o
> >  lan966x-pci-objs		+= lan966x_pci.dtbo.o
> >  obj-$(CONFIG_MCHP_LAN966X_PCI)	+= lan966x-pci.o
> >  obj-y				+= keba/
> > +obj-$(CONFIG_MISC_RP1)		+= rp1/
> > diff --git a/drivers/misc/rp1/Kconfig b/drivers/misc/rp1/Kconfig
> > new file mode 100644
> > index 000000000000..15c443e13389
> > --- /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.
> 
> I haven't tried, but I think if you set CHECK_DTBS=y, then this file 
> will get checked. Applying it to the base DT will not though.

I think we're saying the same thing here, which is that the dtso can be
checked by passing CHECK_DTB=y but it has to be located somewhere under
arch/*/boot/dts. Or maybe I'm misunderstandig what you mean here?

> 
> > + */
> > +
> > +#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..0dd345341c6f
> > --- /dev/null
> > +++ b/drivers/misc/rp1/rp1_pci.c
> > @@ -0,0 +1,366 @@
> > +// 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
> 
> Why all these defines which will never be used because they come from 
> DT?
>

Right, those defines where originally designed to be included from dts, but
previous discussion deemed interrupt numbers to be hardcoded instead of being
specified as mnemonics. In the driver source code I just use RP1_INT_END as the
number of interrupts but I thought that the specific interrupt numbers should
be documented in some way or another. Since no one is currently referencing
those defines, would it be better to just turn those in a multiline comment
just to describe them in a more compact form?

Many thanks,
Andrea

> Rob