Subject: Re: [PATCH 08/11] misc: rp1: RaspberryPi RP1 misc driver

From: Andrea della Porta <[email-masked]>
Date: Tue, 3 Sep 2024 17:15:34 +0200

Hi Krzysztof,

On 18:52 Fri 30 Aug     , Krzysztof Kozlowski wrote:
> On 30/08/2024 15:49, Andrea della Porta wrote:
> > Hi Krzysztof,
> > 
> > On 10:38 Wed 21 Aug     , Krzysztof Kozlowski wrote:
> >> On Tue, Aug 20, 2024 at 04:36:10PM +0200, Andrea della Porta wrote:
> >>> The RaspberryPi RP1 is ia 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-borad peripherals
> >>> by loading a devicetree overlay during driver probe.
> >>> The peripherals are accessed by mapping MMIO registers starting
> >>> from PCI BAR1 region.
> >>> As a minimum driver, the peripherals will not be added to the
> >>> dtbo here, but in following patches.
> >>>
> >>> Link: https://datasheets.raspberrypi.com/rp1/rp1-peripherals.pdf
> >>> Signed-off-by: Andrea della Porta <[email-masked]>
> >>> ---
> >>>  MAINTAINERS                           |   2 +
> >>>  arch/arm64/boot/dts/broadcom/rp1.dtso | 152 ++++++++++++
> >>
> >> Do not mix DTS with drivers.
> >>
> >> These MUST be separate.
> > 
> > Separating the dtso from the driver in two different patches would mean
> > that the dtso patch would be ordered before the driver one. This is because
> > the driver embeds the dtbo binary blob inside itself, at build time. So
> > in order to build the driver, the dtso needs to be there also. This is not
> 
> Sure, in such case DTS will have to go through the same tree as driver
> as an exception. Please document it in patch changelog (---).

Ack.

> 
> > the standard approach used with 'normal' dtb/dtbo, where the dtb patch is
> > ordered last wrt the driver it refers to.
> 
> It's not exactly the "ordered last" that matters, but lack of dependency
> and going through separate tree and branch - arm-soc/dts. Here there
> will be an exception how we handle patch, but still DTS is hardware
> description so should not be combined with driver code.

Ack.

> 
> > Are you sure you want to proceed in this way?
> 
> 
> > 
> >>
> >>>  drivers/misc/Kconfig                  |   1 +
> >>>  drivers/misc/Makefile                 |   1 +
> >>>  drivers/misc/rp1/Kconfig              |  20 ++
> >>>  drivers/misc/rp1/Makefile             |   3 +
> >>>  drivers/misc/rp1/rp1-pci.c            | 333 ++++++++++++++++++++++++++
> >>>  drivers/misc/rp1/rp1-pci.dtso         |   8 +
> >>>  drivers/pci/quirks.c                  |   1 +
> >>>  include/linux/pci_ids.h               |   3 +
> >>>  10 files changed, 524 insertions(+)
> >>>  create mode 100644 arch/arm64/boot/dts/broadcom/rp1.dtso
> >>>  create mode 100644 drivers/misc/rp1/Kconfig
> >>>  create mode 100644 drivers/misc/rp1/Makefile
> >>>  create mode 100644 drivers/misc/rp1/rp1-pci.c
> >>>  create mode 100644 drivers/misc/rp1/rp1-pci.dtso
> >>>
> >>> diff --git a/MAINTAINERS b/MAINTAINERS
> >>> index 67f460c36ea1..1359538b76e8 100644
> >>> --- a/MAINTAINERS
> >>> +++ b/MAINTAINERS
> >>> @@ -19119,9 +19119,11 @@ F:	include/uapi/linux/media/raspberrypi/
> >>>  RASPBERRY PI RP1 PCI DRIVER
> >>>  M:	Andrea della Porta <[email-masked]>
> >>>  S:	Maintained
> >>> +F:	arch/arm64/boot/dts/broadcom/rp1.dtso
> >>>  F:	Documentation/devicetree/bindings/clock/raspberrypi,rp1-clocks.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/arch/arm64/boot/dts/broadcom/rp1.dtso b/arch/arm64/boot/dts/broadcom/rp1.dtso
> >>> new file mode 100644
> >>> index 000000000000..d80178a278ee
> >>> --- /dev/null
> >>> +++ b/arch/arm64/boot/dts/broadcom/rp1.dtso
> >>> @@ -0,0 +1,152 @@
> >>> +// SPDX-License-Identifier: (GPL-2.0 OR MIT)
> >>> +
> >>> +#include <dt-bindings/gpio/gpio.h>
> >>> +#include <dt-bindings/interrupt-controller/irq.h>
> >>> +#include <dt-bindings/clock/rp1.h>
> >>> +#include <dt-bindings/misc/rp1.h>
> >>> +
> >>> +/dts-v1/;
> >>> +/plugin/;
> >>> +
> >>> +/ {
> >>> +	fragment@0 {
> >>> +		target-path="";
> >>> +		__overlay__ {
> >>> +			#address-cells = <3>;
> >>> +			#size-cells = <2>;
> >>> +
> >>> +			rp1: rp1@0 {
> >>> +				compatible = "simple-bus";
> >>> +				#address-cells = <2>;
> >>> +				#size-cells = <2>;
> >>> +				interrupt-controller;
> >>> +				interrupt-parent = <&rp1>;
> >>> +				#interrupt-cells = <2>;
> >>> +
> >>> +				// ranges and dma-ranges must be provided by the includer
> >>> +				ranges = <0xc0 0x40000000
> >>> +					  0x01/*0x02000000*/ 0x00 0x00000000
> >>> +					  0x00 0x00400000>;
> >>
> >> Are you 100% sure you do not have here dtc W=1 warnings?
> > 
> > the W=1 warnings are:
> > 
> > arch/arm64/boot/dts/broadcom/rp1.dtso:37.24-42.7: Warning (simple_bus_reg): /fragment@0/__overlay__/rp1@0/clk_xosc: missing or empty reg/ranges property
> > arch/arm64/boot/dts/broadcom/rp1.dtso:44.26-49.7: Warning (simple_bus_reg): /fragment@0/__overlay__/rp1@0/macb_pclk: missing or empty reg/ranges property
> > arch/arm64/boot/dts/broadcom/rp1.dtso:51.26-56.7: Warning (simple_bus_reg): /fragment@0/__overlay__/rp1@0/macb_hclk: missing or empty reg/ranges property
> > arch/arm64/boot/dts/broadcom/rp1.dtso:14.15-173.5: Warning (avoid_unnecessary_addr_size): /fragment@0/__overlay__: unnecessary #address-cells/#size-cells without "ranges", "dma-ranges" or child "reg" property
> > 
> > I don't see anything related to the ranges line you mentioned.
> 
> Hm, indeed, but I would expect warning about unit address not matching
> ranges/reg.
> 
> > 
> >>
> >>> +
> >>> +				dma-ranges =
> >>> +				// inbound RP1 1x_xxxxxxxx -> PCIe 1x_xxxxxxxx
> >>> +					     <0x10 0x00000000
> >>> +					      0x43000000 0x10 0x00000000
> >>> +					      0x10 0x00000000>;
> >>> +
> >>> +				clk_xosc: clk_xosc {
> >>
> >> Nope, switch to DTS coding style.
> > 
> > Ack.
> > 
> >>
> >>> +					compatible = "fixed-clock";
> >>> +					#clock-cells = <0>;
> >>> +					clock-output-names = "xosc";
> >>> +					clock-frequency = <50000000>;
> >>> +				};
> >>> +
> >>> +				macb_pclk: macb_pclk {
> >>> +					compatible = "fixed-clock";
> >>> +					#clock-cells = <0>;
> >>> +					clock-output-names = "pclk";
> >>> +					clock-frequency = <200000000>;
> >>> +				};
> >>> +
> >>> +				macb_hclk: macb_hclk {
> >>> +					compatible = "fixed-clock";
> >>> +					#clock-cells = <0>;
> >>> +					clock-output-names = "hclk";
> >>> +					clock-frequency = <200000000>;
> >>> +				};
> >>> +
> >>> +				rp1_clocks: clocks@c040018000 {
> >>
> >> Why do you mix MMIO with non-MMIO nodes? This really does not look
> >> correct.
> >>
> > 
> > Right. This is already under discussion here:
> > https://lore.kernel.org/all/ZtBzis5CzQMm8loh@apocalypse/
> > 
> > IIUC you proposed to instantiate the non-MMIO nodes (the three clocks) by
> > using CLK_OF_DECLARE.
> 
> Depends. Where are these clocks? Naming suggests they might not be even
> part of this device. But if these are part of the device, then why this
> is not a clock controller (if they are controllable) or even removed
> (because we do not represent internal clock tree in DTS).

xosc is a crystal connected to the oscillator input of the RP1, so I would
consider it an external fixed-clock. If we were in the entire dts, I would have
put it in root under /clocks node, but here we're in the dtbo so I'm not sure
where else should I put it.

Regarding pclk and hclk, I'm still trying to understand where they come from.
If they are external clocks (since they are fixed-clock too), they should be
in the same node as xosc. CLK_OF_DECLARE does not seem to fit here because
there's no special management of these clocks, so no new clock definition is
needed.
If they are internal tree, I cannot simply get rid of them because rp1_eth node
references these two clocks (see clocks property), so they must be decalred 
somewhere. Any hint about this?.

Many thanks,
Andrea

> Best regards,
> Krzysztof