linux-kernel - Re: [PATCH v2 1/2] dt-bindings: PCI: meson: add DT bindings for Amlogic Meson PCIe controller

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Message-ID: <186a782b20053c42ca8311c421925617d83ffa07.camel@baylibre.com>
Date:   Thu, 30 Aug 2018 10:52:12 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Hanjie Lin <hanjie.lin@...ogic.com>, Rob Herring <robh@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Yue Wang <yue.wang@...ogic.com>,
        Kevin Hilman <khilman@...libre.com>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org,
        Yixun Lan <yixun.lan@...ogic.com>,
        Liang Yang <liang.yang@...ogic.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Qiufang Dai <qiufang.dai@...ogic.com>,
        Jian Hu <jian.hu@...ogic.com>, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: PCI: meson: add DT bindings for
 Amlogic Meson PCIe controller

On Thu, 2018-08-30 at 15:37 +0800, Hanjie Lin wrote:
> 
> On 2018/8/29 8:41, Rob Herring wrote:
> > On Mon, Aug 27, 2018 at 04:55:20PM +0800, Hanjie Lin wrote:
> > > 
> > > 
> > > On 2018/8/24 16:22, Jerome Brunet wrote:
> > > > On Fri, 2018-08-24 at 15:36 +0800, Hanjie Lin wrote:
> > > > > From: Yue Wang <yue.wang@...ogic.com>
> > > > > 
> > > > > The Amlogic Meson PCIe host controller is based on the Synopsys DesignWare
> > > > > PCI core. This patch adds documentation for the DT bindings in Meson PCIe
> > > > > controller.
> > > > > 
> > > > > Signed-off-by: Yue Wang <yue.wang@...ogic.com>
> > > > > Signed-off-by: Hanjie Lin <hanjie.lin@...ogic.com>
> > > > > ---
> > > > >  .../devicetree/bindings/pci/amlogic,meson-pcie.txt | 63 ++++++++++++++++++++++
> > > > >  1 file changed, 63 insertions(+)
> > > > >  create mode 100644 Documentation/devicetree/bindings/pci/amlogic,meson-pcie.txt
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/pci/amlogic,meson-pcie.txt b/Documentation/devicetree/bindings/pci/amlogic,meson-pcie.txt
> > > > > new file mode 100644
> > > > > index 0000000..8a831d1
> > > > > --- /dev/null
> > > > > +++ b/Documentation/devicetree/bindings/pci/amlogic,meson-pcie.txt
> > > > > @@ -0,0 +1,63 @@
> > > > > +Amlogic Meson AXG DWC PCIE SoC controller
> > > > > +
> > > > > +Amlogic Meson PCIe host controller is based on the Synopsys DesignWare PCI core.
> > > > > +It shares common functions with the PCIe DesignWare core driver and
> > > > > +inherits common properties defined in
> > > > > +Documentation/devicetree/bindings/pci/designware-pci.txt.
> > > > > +
> > > > > +Additional properties are described here:
> > > > > +
> > > > > +Required properties:
> > > > > +- compatible:
> > > > > +	should contain "amlogic,axg-pcie" to identify the core.
> > > > > +- reg:
> > > > > +	Should contain the configuration address space.
> > > > > +- reg-names: Must be
> > > > > +	- "elbi"	External local bus interface registers
> > > > > +	- "cfg"		Meson specific registers
> > > > > +	- "config"	PCIe configuration space
> > > > > +- reset-gpios: The GPIO to generate PCIe PERST# assert and deassert signal.
> > > > > +- clocks: Must contain an entry for each entry in clock-names.
> > > > > +- clock-names: Must include the following entries:
> > > > > +	- "pclk"       PCIe GEN 100M PLL clock
> > > > > +	- "port"       PCIe_x(A or B) RC clock gate
> > > > > +	- "general"    PCIe Phy clock
> > > > > +	- "mipi"       PCIe_x(A or B) 100M ref clock gate
> > > > > +- resets: phandle to the reset lines.
> > > > > +- reset-names: must contain "phy" and "peripheral"
> > > > > +       - "port" Port A or B reset
> > > > > +       - "apb" APB reset
> > > > 
> > > > The above description is not coherent (phy <=> port)
> > > > 
> > > 
> > > Yes, this should be port and apb here.
> > > We'll integrate phy driver into ctrl driver, and move phy reset to here also.
> > 
> > Why? That's the wrong thing to do if they are separate h/w blocks. You 
> > can do whatever you like in the drivers, but the DT should reflect the 
> > h/w.
> > 
> > Rob
> > 
> > .
> > 
> 
> We have the dedicated phy driver which only process reset job,
> and we consider that it's too overkill to do just these things .
> So we will integrate phy reset job into the controller driver int the next version.

Rob has a point there. Even if overkill, it does model the HW as it is.
+ I spotted in your v2 that there is also a register access, so not only the
reset

> 
> thanks.