netdev - Re: [PATCH v6 net-next] net: phy: Add Edge-rate driver for Microsemi PHYs.

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Date:   Tue, 4 Oct 2016 17:56:50 +0530
From:   Raju Lakkaraju <Raju.Lakkaraju@...rosemi.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     <netdev@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <f.fainelli@...il.com>, <Allan.Nielsen@...rosemi.com>
Subject: Re: [PATCH v6 net-next] net: phy: Add Edge-rate driver for Microsemi
 PHYs.

Hi Andrew,

Thank you for review comment.
In another thread, I wrote my comment as below.

-----------------------------------------------------------------
> In edge_table, remove the -'s and call edge_rate_magic_get with 
> positive values. The table is also missing "static const".
> edge_rate_magic_get is missing its prefix, so keeping the name space 
> clean.
> 

I will add "static const" to table and also add prefix vsc85xx_ to edge_rate_magic_get function.

Regarding remove the -'s in table, PHY data sheet descript the concept of edge rate with table. I would like to keep the same table in driver.

> Since you are using real values, you can remove mscc-phy-vsc8531.h.
-------------------------------------------------------------------------

But I did not see your comment. I though you accepted to keep the table
as in PHY Data sheet. 

Is any thing wrong if i keep in table with '-' (minus) values?

Thanks,
Raju.

On Tue, Oct 04, 2016 at 01:51:32PM +0200, Andrew Lunn wrote:
> EXTERNAL EMAIL
> 
> 
> On Tue, Oct 04, 2016 at 05:11:12PM +0530, Raju Lakkaraju wrote:
> > From: Raju Lakkaraju <Raju.Lakkaraju@...rosemi.com>
> >
> > Edge-rate:
> > As system and networking speeds increase, a signal's output transition,
> > also know as the edge rate or slew rate (V/ns), takes on greater importance
> > because high-speed signals come with a price. That price is an assortment of
> > interference problems like ringing on the line, signal overshoot and
> > undershoot, extended signal settling times, crosstalk noise, transmission
> > line reflections, false signal detection by the receiving device and
> > electromagnetic interference (EMI) -- all of which can negate the potential
> > gains designers are seeking when they try to increase system speeds through
> > the use of higher performance logic devices. The fact is, faster signaling
> > edge rates can cause a higher level of electrical noise or other type of
> > interference that can actually lead to slower line speeds and lower maximum
> > system frequencies. This parameter allow the board designers to change the
> > driving strange, and thereby change the EMI behavioral.
> >
> > Edge-rate parameters (vddmac, edge-slowdown) get from Device Tree.
> >
> > Tested on Beaglebone Black with VSC 8531 PHY.
> >
> > Signed-off-by: Raju Lakkaraju <Raju.Lakkaraju@...rosemi.com>
> >
> > ---
> > All the review comments updated and resending for review.
> >
> > Change set:
> > v1:
> > - Initial version of Edge-rate driver add by using IOCTL.
> > v2:
> > - Changed edge-rate parameter to Device Tree with magic number.
> > v3:
> > - Added Device Tree documentati0n and edge-rate parameter table.
> >   Added probe function initialize the vsc8531 private data structure.
> > v4:
> > - As per review comment, Device Tree parameters (vddmac, edge-slowdown)
> >   added.
> > v5:
> > - As per review comment, Device Tree Document parameters (vddmac,
> >   edge-slowdown) real numbers added. Table number changed from 5 to 1.
> > v6:
> > - As per review comment, Removed Device Tree header file. Removed MACROs
> >   and add ARRAYSIZE
> 
> But you ignored my request to make the table values positive, and to
> enforce an exact match in the table.
> 
> NACK
> 
>         Andrew