From: Roger Quadros <rogerq@ti.com>
To: Florian Fainelli <f.fainelli@gmail.com>, <davem@davemloft.net>,
Andrew Lunn <andrew@lunn.ch>
Cc: <tony@atomide.com>, <nsekhar@ti.com>, <jsarha@ti.com>,
<netdev@vger.kernel.org>, <linux-omap@vger.kernel.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 net-next] mdio_bus: Issue GPIO RESET to PHYs.
Date: Fri, 21 Apr 2017 11:04:41 +0300 [thread overview]
Message-ID: <a04bb6e2-4223-6baa-05d2-665fa99f7d48@ti.com> (raw)
In-Reply-To: <fa24ae98-3d4f-4b11-bbb4-485b9ed41ed7@gmail.com>
Hi Florian,
On 21/04/17 04:23, Florian Fainelli wrote:
> Hi Roger,
>
> On 04/20/2017 07:11 AM, Roger Quadros wrote:
>> Some boards [1] leave the PHYs at an invalid state
>> during system power-up or reset thus causing unreliability
>> issues with the PHY which manifests as PHY not being detected
>> or link not functional. To fix this, these PHYs need to be RESET
>> via a GPIO connected to the PHY's RESET pin.
>>
>> Some boards have a single GPIO controlling the PHY RESET pin of all
>> PHYs on the bus whereas some others have separate GPIOs controlling
>> individual PHY RESETs.
>>
>> In both cases, the RESET de-assertion cannot be done in the PHY driver
>> as the PHY will not probe till its reset is de-asserted.
>> So do the RESET de-assertion in the MDIO bus driver.
>>
>> [1] - am572x-idk, am571x-idk, a437x-idk
>>
>> Signed-off-by: Roger Quadros <rogerq@ti.com>
>
> A few comments on the binding and the code, sorry for this late review.
No problem at all.
>
>> +Example :
>> +This example shows these optional properties, plus other properties
>> +required for the TI Davinci MDIO driver.
>> +
>> + davinci_mdio: ethernet@0x5c030000 {
>> + compatible = "ti,davinci_mdio";
>> + reg = <0x5c030000 0x1000>;
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> +
>> + reset-gpios = <&gpio2 5 GPIO_ACTIVE_LOW>;
>> + reset-delay-us = <2>; /* PHY datasheet states 1uS min */
>
> us is micro seconds, uS is micro siemens.
OK.
>
>> +
>> + ethphy0: ethernet-phy@1 {
>> + reg = <1>;
>> + };
>> +
>> + ethphy1: ethernet-phy@3 {
>> + reg = <3>;
>> + };
>> + };
>
>>
>> + /* de-assert bus level PHY GPIO resets */
>> + for (i = 0; i < bus->num_reset_gpios; i++) {
>> + gpiod = devm_gpiod_get_index(&bus->dev, "reset", i,
>> + GPIOD_OUT_LOW);
>> + if (IS_ERR(gpiod)) {
>> + err = PTR_ERR(gpiod);
>> + if (err != -ENOENT) {
>> + pr_err("mii_bus %s couldn't get reset GPIO\n",
>> + bus->id);
>
> Could we use dev_err(&bus->dev) here to better identify which MDIO bus
> is returning the problem?
Sure.
>
>> + return err;
>
> Should we somehow "unwind" the reset lines we were able to successfully
> take out of reset and therefore put back into reset state? How about
> mdiobus_unregister()? Should we have similar code there, if not for
> correctness to be more power efficient?
Al right.
>
>> + }
>> + } else {
>> + gpiod_set_value_cansleep(gpiod, 1);
>> + udelay(bus->reset_delay_us);
>> + gpiod_set_value_cansleep(gpiod, 0);
>
> Does that work even if the polarity of the reset line is active low?
>
Yes. The polarity needs to be specified at DT as explained by Andrew already.
cheers,
-roger
next prev parent reply other threads:[~2017-04-21 8:05 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-05 8:33 [PATCH] net: davinci_mdio: add GPIO reset logic Roger Quadros
2017-04-05 15:03 ` Andrew Lunn
2017-04-06 9:15 ` Roger Quadros
2017-04-06 12:05 ` Andrew Lunn
2017-04-06 16:48 ` Roger Quadros
2017-04-08 13:55 ` David Miller
2017-04-08 15:10 ` Andrew Lunn
2017-04-08 15:18 ` Florian Fainelli
2017-04-10 7:52 ` Roger Quadros
2017-04-19 9:24 ` [PATCH] mdio_bus: Issue GPIO RESET to PHYs Roger Quadros
2017-04-19 11:39 ` Andrew Lunn
2017-04-19 11:56 ` Roger Quadros
2017-04-19 13:38 ` Andrew Lunn
2017-04-20 7:58 ` Roger Quadros
2017-04-20 8:39 ` [PATCH v2] " Roger Quadros
2017-04-20 13:13 ` Andrew Lunn
2017-04-20 13:56 ` Roger Quadros
2017-04-20 14:11 ` [PATCH v3 net-next] " Roger Quadros
2017-04-21 1:12 ` Andrew Lunn
2017-04-21 1:23 ` Florian Fainelli
2017-04-21 1:38 ` Andrew Lunn
2017-04-21 8:04 ` Roger Quadros [this message]
2017-04-21 13:15 ` [PATCH v4 " Roger Quadros
2017-04-21 13:31 ` Lars-Peter Clausen
2017-04-23 23:35 ` Andrew Lunn
2017-04-24 9:04 ` Roger Quadros
2017-04-24 16:32 ` Florian Fainelli
2017-04-25 16:22 ` Lars-Peter Clausen
2017-04-25 16:31 ` Florian Fainelli
2017-04-26 10:46 ` Roger Quadros
2017-04-26 12:27 ` Andrew Lunn
2017-04-26 10:43 ` Roger Quadros
2017-04-24 16:40 ` David Miller
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