Re: [PATCH v3 06/11] dt-bindings: PCI: Update the RK3399 example to a valid one

From: Rick Wertenbroek <rick.wertenbroek@gmail.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: alberto.dassatti@heig-vd.ch, damien.lemoal@opensource.wdc.com,
	xxm@rock-chips.com, "Shawn Lin" <shawn.lin@rock-chips.com>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Rob Herring" <robh@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Heiko Stuebner" <heiko@sntech.de>,
	"Johan Jonker" <jbx6244@gmail.com>,
	"Brian Norris" <briannorris@chromium.org>,
	"Caleb Connolly" <kc@postmarketos.org>,
	"Corentin Labbe" <clabbe@baylibre.com>,
	"Judy Hsiao" <judyhsiao@chromium.org>,
	"Lin Huang" <hl@rock-chips.com>,
	"Arnaud Ferraris" <arnaud.ferraris@collabora.com>,
	"Hugh Cole-Baker" <sigmaris@gmail.com>,
	linux-pci@vger.kernel.org, linux-rockchip@lists.infradead.org,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 06/11] dt-bindings: PCI: Update the RK3399 example to a valid one
Date: Tue, 4 Apr 2023 10:58:45 +0200	[thread overview]
Message-ID: <CAAEEuhrnp1QyP498V1wzyLv6KvfRCpNidF9NJpzg+kofWqrJtA@mail.gmail.com> (raw)
In-Reply-To: <d9afc07f-0346-1fe7-907c-261e4c6f92cd@linaro.org>

On Tue, Apr 4, 2023 at 10:45 AM Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> On 04/04/2023 10:24, Rick Wertenbroek wrote:
> > Update the example in the documentation a valid example.
> > The default max-outbound-regions is 32 but the example showed 16.
>
> This is not reason to be invalid. It is perfectly fine to change default
> values to desired ones. What is not actually obvious is to change some
> value to a default one, instead of removing it...

Hello, the example value <0x0 0x80000000 0x0 0x20000>; is plain wrong
and will crash the kernel. This is a value that point to an address that falls
in the DDR RAM region but depending on the amount of RAM on the
board this address may not even exist (e.g., board with 2GB or less).

Also this address requires pointing to where the PCIe controller has the
windows from AXI Physical space to PCIe space. This address is
allocated when the SoC address map is created so it can only be that
one unless rockchip refabs the SoC with another address map.

The example never worked with the values given as reported by e.g.,
https://stackoverflow.com/questions/73586703/device-tree-issues-with-rockpro64-pcie-endpoint
and here they set it to 0 (base of the DDR, which is a "valid" address
as to it exists even on boards with less than 2GB) but it is still wrong
to do so.

>
> > Address for mem-base was invalid. Added pinctrl.
> >
> > Signed-off-by: Rick Wertenbroek <rick.wertenbroek@gmail.com>
> > ---
> >  .../devicetree/bindings/pci/rockchip,rk3399-pcie-ep.yaml  | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/pci/rockchip,rk3399-pcie-ep.yaml b/Documentation/devicetree/bindings/pci/rockchip,rk3399-pcie-ep.yaml
> > index 88386a6d7011..0c67e96096eb 100644
> > --- a/Documentation/devicetree/bindings/pci/rockchip,rk3399-pcie-ep.yaml
> > +++ b/Documentation/devicetree/bindings/pci/rockchip,rk3399-pcie-ep.yaml
> > @@ -47,14 +47,15 @@ examples:
> >
> >          pcie-ep@f8000000 {
> >              compatible = "rockchip,rk3399-pcie-ep";
> > -            reg = <0x0 0xfd000000 0x0 0x1000000>, <0x0 0x80000000 0x0 0x20000>;
> > -            reg-names = "apb-base", "mem-base";
>
> Reg (and reg-names) is usually second property, why moving it? What is
> incorrect in the placement?

Sorry, I was not aware there was a standard ordering, the reason I moved
so that it follows the ordering I had in the entry I added to the .dtsi file
(which therefore also is in the non standard order).
Could you be kind enough to share with me the link to the documentation
for the order, so that I can both update the .dtsi and this file, this
way it will
be in order and coherent for both. Thank you.

>
> > +            rockchip,max-outbound-regions = <32>;
> >              clocks = <&cru ACLK_PCIE>, <&cru ACLK_PERF_PCIE>,
> >                <&cru PCLK_PCIE>, <&cru SCLK_PCIE_PM>;
> >              clock-names = "aclk", "aclk-perf",
> >                      "hclk", "pm";
> >              max-functions = /bits/ 8 <8>;
> >              num-lanes = <4>;
> > +            reg = <0x0 0xfd000000 0x0 0x1000000>, <0x0 0xfa000000 0x0 0x2000000>;
> > +            reg-names = "apb-base", "mem-base";
> >              resets = <&cru SRST_PCIE_CORE>, <&cru SRST_PCIE_MGMT>,
> >                <&cru SRST_PCIE_MGMT_STICKY>, <&cru SRST_PCIE_PIPE> ,
> >                <&cru SRST_PCIE_PM>, <&cru SRST_P_PCIE>, <&cru SRST_A_PCIE>;
> > @@ -62,7 +63,8 @@ examples:
> >                      "pm", "pclk", "aclk";
> >              phys = <&pcie_phy 0>, <&pcie_phy 1>, <&pcie_phy 2>, <&pcie_phy 3>;
> >              phy-names = "pcie-phy-0", "pcie-phy-1", "pcie-phy-2", "pcie-phy-3";
> > -            rockchip,max-outbound-regions = <16>;
> > +            pinctrl-names = "default";
> > +            pinctrl-0 = <&pcie_clkreqnb_cpm>;
> >          };
> >      };
> >  ...
>
> Best regards,
> Krzysztof
>

Thank you for you comments,
Sincerely
Rick