linux-kernel - Re: [PATCH v1 1/2] dt/bindings/usb: Add bindings for PIC32 MUSB driver.

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Date:	Thu, 7 Apr 2016 16:12:20 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Purna Chandra Mandal <purna.mandal@...rochip.com>,
	linux-kernel@...r.kernel.org
Cc:	Rob Herring <robh+dt@...nel.org>, linux-usb@...r.kernel.org,
	Joshua Henderson <digitalpeer@...italpeer.com>,
	devicetree@...r.kernel.org, Kumar Gala <galak@...eaurora.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v1 1/2] dt/bindings/usb: Add bindings for PIC32 MUSB
 driver.

On 4/7/2016 4:02 PM, Purna Chandra Mandal wrote:

>>> Document devicetree binding for the USB controller
>>
>>     Device tree.
>>
> ack.
>
>>> and USB Phy found on Microchip PIC32 class devices.
>>
>>     PHY.
>>
> ack.
>
>>> Signed-off-by: Purna Chandra Mandal <purna.mandal@...rochip.com>
>>>
>>> ---
>>>
>>>    .../bindings/usb/microchip,pic32-musb.txt          | 67 ++++++++++++++++++++++
>>>    1 file changed, 67 insertions(+)
>>>    create mode 100644 Documentation/devicetree/bindings/usb/microchip,pic32-musb.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/usb/microchip,pic32-musb.txt b/Documentation/devicetree/bindings/usb/microchip,pic32-musb.txt
>>> new file mode 100644
>>> index 0000000..e1cec9d
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/usb/microchip,pic32-musb.txt
>>> @@ -0,0 +1,67 @@
>>> +Microchip PIC32 MUSB DRC/OTG controller
>>> +-------------------------------------------
>>> +
>>> +Required properties:
>>> + - compatible       : should be "microchip,pic32mzda-usb".
>>> + - reg              : offset and length of "MUSB Core Registers" and
>>> +                      "USB Clock & Reset Registers".
>>> + - reg-names        : should be "mc", and "usbcr" in order
>>> + - clocks           : clock specifier for the musb controller clock
>>> + - clock-names      : should be "usb_clk"
>>> + - interrupts       : interrupt number for MUSB Core General interrupt
>>> +                      and DMA interrupt
>>> + - interrupt-names  : must be "mc" and "dma" in order.
>>> + - phys             : phy specifier for the otg phy.
>>> + - dr_mode          : should be one of "host", "peripheral" or "otg".
>>> + - mentor,multipoint: Should be "1" indicating the musb controller supports
>>> +                      multipoint. This is MUSB configuration-specific setting.
>>> + - mentor,num-eps   : Specifies the number of endpoints. This is also a
>>> +                      MUSB configuration-specific setting. Should be set to "8".
>>> + - mentor,ram-bits  : Specifies the ram address size. Should be set to "11".
>>> + - mentor,power     : Should be "500". This signifies the controller can supply
>>> +                      up to 500mA when operating in host mode.
>>
>>     No, these "nentor" prefixed parameters must be determined from the "compatible" prop.
>>
> Prefix "mentor" here is used to signify configuration of the MUSB controller IP, not
> specifics of the chip or glue logic.

    I know.

> Please suggest if replacing with "microchip" makes it better.

    No, nothing of that sort. These parameters are probably fixed for the said 
PIC32 implementation? If so, they shouldn't appear as the node props but 
should instead be hard-coded in the glue layer. Don't look at the OMAP glues, 
they are a bad example.

>>> + - phys             : phandle of the USB phy.

    "phys" are reserved for use by the drivers/phy/, while your PHY seems to 
be controlled by drivers/usb/phy/. Please rename this property to "usb-phy".

>>> +                      interrupt number for over-current detection logic.
>>> +
>>> +Optional properties:
>>> + - microchip,fifo-mode: Specifies layout of internal SRAM for end-point fifos.
>>> +                        Should be 0 (default) or 1.

    Probably would be better as a boolean prop...

[...]

MBR, Sergei