Re: [PATCH v5 3/5] dt-bindings: phy: tegra: Add Tegra194 support

[JC Kuo <jckuo@nvidia.com>]

On 1/4/20 6:39 AM, Rob Herring wrote:
> On Fri, Jan 03, 2020 at 04:18:12PM +0800, JC Kuo wrote:
>> Extend the bindings to cover the set of features found in Tegra194.
>> Note that, technically, there are four more supplies connected to the
>> XUSB pad controller (DVDD_PEX, DVDD_PEX_PLL, HVDD_PEX and HVDD_PEX_PLL)
>> , but the power sequencing requirements of Tegra194 require these to be
>> under the control of the PMIC.
>>
>> Tegra194 XUSB PADCTL supports up to USB 3.1 Gen 2 speed, however, it
>> is possible for some platforms have long signal trace that could not
>> provide sufficient electrical environment for Gen 2 speed. This patch
>> adds a "maximum-speed" property to usb3 ports which can be used to
>> specify the maximum supported speed for any particular USB 3.1 port.
>> For a port that is not capable of SuperSpeedPlus, "maximum-speed"
>> property should carry "super-speed".
>>
>> Signed-off-by: JC Kuo <jckuo@nvidia.com>
>> ---
>> Changes in v5:
>> - re-use "maximum-speed" instead of adding "nvidia,disable-gen2"
>> Changes in v4: none
>> Changes in v3: none
>> Changes in v2:
>> - fix a typo
>>
>>  .../phy/nvidia,tegra124-xusb-padctl.txt        | 18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt b/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
>> index 9fb682e47c29..7d0089006e67 100644
>> --- a/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
>> +++ b/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
>> @@ -37,6 +37,7 @@ Required properties:
>>    - Tegra132: "nvidia,tegra132-xusb-padctl", "nvidia,tegra124-xusb-padctl"
>>    - Tegra210: "nvidia,tegra210-xusb-padctl"
>>    - Tegra186: "nvidia,tegra186-xusb-padctl"
>> +  - Tegra194: "nvidia,tegra194-xusb-padctl"
>>  - reg: Physical base address and length of the controller's registers.
>>  - resets: Must contain an entry for each entry in reset-names.
>>  - reset-names: Must include the following entries:
>> @@ -62,6 +63,10 @@ For Tegra186:
>>  - vclamp-usb-supply: Bias rail for USB pad. Must supply 1.8 V.
>>  - vddio-hsic-supply: HSIC PHY power supply. Must supply 1.2 V.
>>  
>> +For Tegra194:
>> +- avdd-usb-supply: USB I/Os, VBUS, ID, REXT, D+/D- power supply. Must supply
>> +  3.3 V.
>> +- vclamp-usb-supply: Bias rail for USB pad. Must supply 1.8 V.
>>  
>>  Pad nodes:
>>  ==========
>> @@ -154,6 +159,11 @@ For Tegra210, the list of valid PHY nodes is given below:
>>  - sata: sata-0
>>    - functions: "usb3-ss", "sata"
>>  
>> +For Tegra194, the list of valid PHY nodes is given below:
>> +- usb2: usb2-0, usb2-1, usb2-2, usb2-3
>> +  - functions: "xusb"
>> +- usb3: usb3-0, usb3-1, usb3-2, usb3-3
>> +  - functions: "xusb"
>>  
>>  Port nodes:
>>  ===========
>> @@ -221,6 +231,11 @@ Optional properties:
>>    is internal. In the absence of this property the port is considered to be
>>    external.
>>  
>> +- maximum-speed: Only for Tegra194. A string property that specifies maximum
>> +  supported speed of a usb3 port. Valid values are:
>> +  - "super-speed-plus": default, the usb3 port supports USB 3.1 Gen 2 speed.
> 
> Not defined as a valid value in usb/generic.txt. '-gen2' instead of 
> '-plus' would be clearer IMO. However, is there any need to define the 
> maximum speed possible? The purpose of this property is to limit the 
> speed below the max.
> 
usb_get_maximum_speed(), which parses "maximum-speed" property, indeed handles
string "super-speed-plus". Should "super-speed-plus" be documented in
usb/generic.txt"?

static const char *const speed_names[] = {
	[USB_SPEED_UNKNOWN] = "UNKNOWN",
	[USB_SPEED_LOW] = "low-speed",
	[USB_SPEED_FULL] = "full-speed",
	[USB_SPEED_HIGH] = "high-speed",
	[USB_SPEED_WIRELESS] = "wireless",
	[USB_SPEED_SUPER] = "super-speed",
	[USB_SPEED_SUPER_PLUS] = "super-speed-plus",
};

A proprietary "nvidia,disable-gen2" property was proposed in earlier revision to
"limit the speed below the max". I like it because it fit our needs better and
requires only one line of code change.

   usb3->disable_gen2 = of_property_read_bool(np, "nvidia,disable-gen2");

Should I fallback to that approach?

Thanks,
JC

>> +  - "super-speed": the usb3 port supports USB 3.1 Gen 1 speed only.
>> +
>>  For Tegra124 and Tegra132, the XUSB pad controller exposes the following
>>  ports:
>>  - 3x USB2: usb2-0, usb2-1, usb2-2
>> @@ -233,6 +248,9 @@ For Tegra210, the XUSB pad controller exposes the following ports:
>>  - 2x HSIC: hsic-0, hsic-1
>>  - 4x super-speed USB: usb3-0, usb3-1, usb3-2, usb3-3
>>  
>> +For Tegra194, the XUSB pad controller exposes the following ports:
>> +- 4x USB2: usb2-0, usb2-1, usb2-2, usb2-3
>> +- 4x super-speed USB: usb3-0, usb3-1, usb3-2, usb3-3
>>  
>>  Examples:
>>  =========
>> -- 
>> 2.17.1
>>