Re: [PATCH v4 2/4] Documentation: Add APM X-Gene SoC 15Gbps Multi-purpose PHY driver binding documentation

[Loc Ho <lho@apm.com>]

Hi,

> On Thursday 12 December 2013, Loc Ho wrote:
>> +- reg                  : First PHY memory resource is the SDS PHY access
>> +                         resource.
>> +                         Second PHY memory resoruce is the clock and reset
>> +                         resources.
>> +                         Third PHY memory resource is the SDS PHY access
>> +                         resource outside of the IP if it is type
>> +                         "apm,xgene-phy-ext".
>
> Why do the "clock and reset" resources not use a clock driver and a reset
> driver?
>
> I would expect these to get replaced with
>
>         clocks          : Reference to external clock input
>         resets          : Reference to reset controller input
[Loc Ho]
The clock register has bit for the SDS interface, each sata ports,
CSR, AXI interface, and the PM (power management) interface. The clock
and CSR for all these are enabled by the host controller driver.
Unfortunately, during calibration the SATA ports clocks must not be
enable. This sequence is required by the hardware itself. Unless I
separate out the two, this requirement is handled by the PHY. If you
believe this is needed, I can have two separate clocks but it is over
kill. You can look at function xgene_phy_sata_setup_preclk and
xgene_phy_sata_setup_postclk.

>
>> +Optional properties:
>> +- status             : Shall be "ok" if enabled or "disabled" if disabled.
>> +                       Default is "ok".
>> +- apm,tx-eye-tuning  : Manual control to fine tune the capture of the serial
>> +                       bit lines from the automatic calibrated position.
>> +                       Two set of 3-tuple setting for Gen1, Gen2, and Gen3.
>> +                       Range from 0 to 0x7f in unit of one bit period.
>> +                       Default is 0xa.
>
> What does gen1, gen2 and gen3 refer to? Is this PCIe, SATA or serdes generations
> or all of them?
[Loc Ho]
Douglas already commented on this. Gen1 in SATA term is 1.5Gbps, Gen2
is 3.0Gbps, and Gen3 is 6Gbps.

>
> Why are there two sets?
[Loc Ho]
Each controller has two SATA ports - one set for each port.

>
> Will this have to change if you add PCIe support?
[Loc Ho]
So far, we don't see a need to use override setting for PCIe

>
> I would suggest using decimal notation here instead of hexadecimal since you
> are dealing with numbers couting things. Same for the others.
[Loc Ho]
Okay... for future version.

>
>> +- apm,tx-eye-direction       : Eye tuning manual control direction. 0 means sample
>> +                       data earlier than the nominal sampling point. 1 means
>> +                       sample data later than the nominal sampling point.
>> +                       Two set of 3-tuple setting for Gen1, Gen2, and Gen3.
>> +                       Default is 0x0.
>> +
>> +- apm,tx-boost-gain  : Frequency boost AC (LSB 3-bit) and DC (2-bit)
>> +                       gain control. Two set of 3-tuple setting for Gen1,
>> +                       Gen2, and Gen3. Range is between 0 to 0x1f in unit
>> +                       of dB. Default is 0x3.
>> +
>> +- apm,tx-amplitude   : Amplitude control. Two set of 3-tuple setting for
>> +                       Gen1, Gen2, and Gen3. Range is between 0 to 0xf in
>> +                       unit of 13.3mV. Default is 0xf.
>
> Units of 13.3mV don't seem to be useful as a generic measurement. I'd
> recommend using milivolts or microvolts.
[Loc Ho]
Each unit is 13.3mV. If I use millivolt, then someone can set fraction
which will get round up or down. If you still strongly suggest this is
required, then fine.

>
>> +- apm,tx-pre-cursor1 : 1st pre-cursor emphasis taps control. Two set of
>> +                       3-tuple setting for Gen1, Gen2, and Gen3. Range is
>> +                       between 0 to 0xf in unit of 18.2mV. Default is 0x0.
>> +- apm,tx-pre-cursor2 : 2st pre-cursor emphasis taps control. Two set of
>> +                       3-tuple setting for Gen1, Gen2, and Gen3. Range is
>> +                       between 0 to 0x7 in unit of 18.2mV. Default is 0x0.
>> +- apm,tx-post-cursor : Post-cursor emphasis taps control. Two set of
>> +                       3-tuple setting for Gen1, Gen2, and Gen3. Range is
>> +                       between 0 to 0x1f in unit of 18.2mV. Default is 0xf.
>
> Same here.
>
>> +- apm,tx-speed               : Tx operating speed. One set of 3-tuple for
>> +                       Gen1 (0x1), Gen2 (0x3), and Gen3 (0x7). Default is
>> +                       0x7.
>
> I'm completely confused by this description. Can you rephrase this?
> It sounds like the only possible values are <1 3 7> for this property.
[Loc Ho]
Douglas already comment on this. If you believe this needs to be
rephrased, then let me know.

-Loc