netdev - Re: [PATCH v2 3/5] drivers: net: phy: Add MDIO driver

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Date:	Wed, 6 Jul 2016 16:44:44 -0700
From:	Iyappan Subramanian <isubramanian@....com>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, patches <patches@....com>,
	Matthias Brugger <matthias.bgg@...il.com>
Subject: Re: [PATCH v2 3/5] drivers: net: phy: Add MDIO driver

Hi Andrew,

On Tue, Jul 5, 2016 at 6:49 AM, Andrew Lunn <andrew@...n.ch> wrote:
> On Mon, Jun 06, 2016 at 10:12:35AM -0700, Iyappan Subramanian wrote:
>> Hi Andrew,
>>
>> Thanks for the review.
>>
>> On Tue, May 31, 2016 at 6:11 PM, Andrew Lunn <andrew@...n.ch> wrote:
>> > On Tue, May 31, 2016 at 05:10:38PM -0700, Iyappan Subramanian wrote:
>> >> +static int xgene_mdio_reset(struct xgene_mdio_pdata *pdata)
>> >> +{
>> >> +     int ret;
>> >> +
>> >> +     if (pdata->mdio_id == XGENE_MDIO_RGMII) {
>> >> +             if (pdata->dev->of_node) {
>> >> +                     clk_prepare_enable(pdata->clk);
>> >> +                     clk_disable_unprepare(pdata->clk);
>> >> +                     clk_prepare_enable(pdata->clk);
>> >
>> > Hi Iyappan
>> >
>> > Is that a workaround for a hardware problem? If so, i would suggest
>> > adding a comment, to stop people submitting a patch simplifying it.
>>
>> Hardware expects this clock sequence.  I'll add comment as you suggested.
>
> What exactly does the hardware require? Is this a workaround for a bug
> in the clock generator? Or a workaround for a bug in the MDIO device?

Hardware requires a clock pulse.  There is no bug.

>
> If it is a clock generator bug, i think the fix should be in the clock
> driver. If this is bug in the MDIO device, do you need a sleep in
> there, so you actually have the clock ticking/not ticking for a time?
> Since these calls can all sleep, you have no idea how long/sort the
> clock will be enabled/disabled.
>
>       Andrew