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SubjectRE: [PATCH 1/3] phy: keystone: serdes driver for gbe 10gbe and pcie
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> -----Original Message-----
> From: Mark Rutland [mailto:mark.rutland@arm.com]
> Sent: Tuesday, October 13, 2015 2:33 PM
> To: Kwok, WingMan
> Cc: robh+dt@kernel.org; pawel.moll@arm.com;
> ijc+devicetree@hellion.org.uk; galak@codeaurora.org; KISHON VIJAY
> ABRAHAM; Quadros, Roger; Karicheri, Muralidharan; bhelgaas@google.com;
> ssantosh@kernel.org; linux@arm.linux.org.uk;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; linux-
> pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org
> Subject: Re: [PATCH 1/3] phy: keystone: serdes driver for gbe 10gbe
> and pcie
>
> On Tue, Oct 13, 2015 at 02:04:22PM -0400, WingMan Kwok wrote:
> > On TI's Keystone platforms, several peripherals such as the
> > gbe ethernet switch, 10gbe ethernet switch and PCIe controller
> > require the use of a SerDes for converting SoC parallel data into
> > serialized data that can be output over a high-speed electrical
> > interface, and also converting high-speed serial input data
> > into parallel data that can be processed by the SoC. The
> > SerDeses used by those peripherals, though they may be different,
> > are largely similar in functionality and setup.
> >
> > This patch provides a SerDes phy driver implementation that can be
> > used by the above mentioned peripheral drivers to configure their
> > respective SerDeses.
> >
> > Signed-off-by: WingMan Kwok <w-kwok2@ti.com>
> > ---
> > Documentation/devicetree/bindings/phy/ti-phy.txt | 256 +++
> > drivers/phy/Kconfig | 8 +
> > drivers/phy/Makefile | 1 +
> > drivers/phy/phy-keystone-serdes.c | 2465
> ++++++++++++++++++++++
> > 4 files changed, 2730 insertions(+)
> > create mode 100644 drivers/phy/phy-keystone-serdes.c
> >
> > diff --git a/Documentation/devicetree/bindings/phy/ti-phy.txt
> b/Documentation/devicetree/bindings/phy/ti-phy.txt
> > index 9cf9446..231716e 100644
> > --- a/Documentation/devicetree/bindings/phy/ti-phy.txt
> > +++ b/Documentation/devicetree/bindings/phy/ti-phy.txt
> > @@ -115,4 +115,260 @@ sata_phy: phy@4A096000 {
> > clock-names = "sysclk", "refclk";
> > syscon-pllreset = <&scm_conf 0x3fc>;
> > #phy-cells = <0>;
> > +
> > +TI Keystone SerDes PHY
> > +======================
> > +
> > +Required properties:
> > + - compatible: should be one of
> > + * "ti,keystone-serdes-gbe"
> > + * "ti,keystone-serdes-xgbe"
> > + * "ti,keystone-serdes-pcie"
> > + - reg:
> > + * base address and length of the SerDes register set
> > + - reg-names:
> > + * "reg_serdes"
> > + - name of the reg SerDes register set
>
> Just describe reg in terms of reg-names, and don't bother with the
> "reg_" prefix, we know this is a reg entry:
>
> - reg: a list of address and length pairs, corresponding to entires in
> reg-names
>
> - reg-names: should contain:
> * "serdes"
>
> > + - #phy-cells:
> > + * From the generic phy bindings, must be 0;
> > + - max-lanes:
> > + * Number of lanes in SerDes.
>
> Why is this not "num-lanes"? Why do you even need this?
>

will change to "num-lanes".

serdes on different peripherals have different number of
lanes and each individual lane can be enabled or disabled.

> > + - phy-type: should be one of
> > + * "sgmii"
> > + * "xge"
> > + * "pcie"
> > +
> > +Optional properties:
> > + - syscon-peripheral:
> > + * Handle to the subsystem register region of the peripheral
> > + inside which the SerDes exists.
> > + - syscon-link:
> > + * Handle to the Link register region of the peripheral inside
> > + which the SerDes exists. Example: it is the PCSR register
> > + region in the case of 10gbe.
> > + - refclk-khz:
> > + * Reference clock rate of SerDes in kHz.
>
> Surely this should be an actual clock?
>

ok, this is not actually needed and will remove

> > + - link-rate-kbps:
> > + * SerDes link rate to be configured, in kbps.
>
> Why does this need to be in the binding? How does one derive the
> correct
> value?
>

a serdes can be configured at different link rates. for example,
the 10gbe serdes can be configured at 1.25G link rate to support
1gbe on the 10gbe switch.

> > + - control-rate:
> > + * Lane control rate
> > + 0: full rate
> > + 1: half rate
> > + 2: quarter rate
>
> Likewise on both points.

the serdes is a generic hardware block that needs to be configured
with the proper link-rate and lane control rate.

>
> > + - rx-start:
> > + * Initial lane rx equalizer attenuation and boost configurations.
> > + * Must be array of 2 integers.
> > + - rx-force:
> > + * Forced lane rx equalizer attenuation and boost configurations.
> > + * Must be array of 2 integers.
> > + - tx-coeff:
> > + * Lane c1, c2, cm, attenuation and regulator outpust voltage
> > + configurations.
> > + * Must be array of 5 integers.
>
> s/outpust/output/
>

ok.

> > + - debug:
> > + * enable more debug messages.
>
> NAK.
>
> This is a driver option, and belongs on the kernel command line. It
> does
> not describe the hardware, and does not belong in the DT.
>

will remove.

> > +Example for Keystone K2E GBE:
> > +-----------------------------
> > +
> > +gbe_serdes0: gbe_serdes@232a000 {
> > + #phy-cells = <0>;
> > + compatible = "ti,keystone-serdes-gbe";
> > + reg = <0x0232a000 0x2000>;
> > + reg-names = "reg_serdes";
> > + refclk-khz = <156250>;
> > + link-rate-kbps = <1250000>;
> > + phy-type = "sgmii";
> > + max-lanes = <4>;
> > + lane0 {
> > + control-rate = <2>; /* quart */
> > + rx-start = <7 5>;
> > + rx-force = <1 1>;
> > + tx-coeff = <0 0 0 12 4>;
> > + /* c1 c2 cm att vreg */
> > + };
> > + lane1 {
> > + control-rate = <2>; /* quart */
> > + rx-start = <7 5>;
> > + rx-force = <1 1>;
> > + tx-coeff = <0 0 0 12 4>;
> > + /* c1 c2 cm att vreg */
> > + };
>
> The binding didn't describe the sub-nodes, and which properties belong
> to them.
>

will add descriptions for lane nodes

> Don't use magic names. Define a new address space, and use reg to
> identify lanes.
>

will update to the following

lanes {
lane@0 {
reg = <0>;
...
};

lane@1 {
reg = <1>;
...
};
};


> > + if (of_find_property(np, "disable", NULL))
> > + lc->enable = 0;
> > + else
> > + lc->enable = 1;
>
> This was not described in the binding, and uses the wrong accessor.
> What
> is this for?

after the above mentioned update, this will become: status = "disabled/ok".
>
> > + if (of_find_property(np, "loopback", NULL))
> > + lc->loopback = 1;
> > + else
> > + lc->loopback = 0;
>
> Likewise.

will add documentation

>
> > + if (of_property_read_bool(np, "syscon-peripheral")) {
> > + sc->peripheral_regmap =
> > + syscon_regmap_lookup_by_phandle(np,
> > + "syscon-peripheral");
>
> Can't you always call syscon_regmap_lookup_by_phandle, then check the
> return value to see if the property existed?
>
> You clearly know that of_property_read_bool exists, why did you not
> use
> it to read properties which are boolean?
>

ok.

> > + if (of_property_read_bool(np, "syscon-link")) {
> > + sc->pcsr_regmap =
> > + syscon_regmap_lookup_by_phandle(np, "syscon-link");
>
> Likewise.
>

ok.

> > + sc->debug = of_property_read_bool(np, "debug");
>
> As stated above, NAK for this property.
>

will remove.

> > +
> > + if (of_find_property(np, "rx-force-enable", NULL))
> > + sc->rx_force_enable = 1;
> > + else
> > + sc->rx_force_enable = 0;
>
> Not in the binding, and uses the wrong accessor.
>

ok. will update the binding and change of_find_property to
of_property_read_bool.

> > +
> > + for (i = 0; i < sc->lanes; i++) {
> > + sprintf(&name[4], "%d", i);
> > + lp = of_find_node_by_name(np, name);
> > + if (lp) {
> > + if (kserdes_get_lane_bindings(dev, lp, &sc->lane[i]))
> > + return -EINVAL;
> > + }
> > + }
>
> As above, use reg, not magic names.

ok.

Thanks,
WingMan
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