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

[Raju Lakkaraju]

Hi Andrew,

Thank you for review comments.
I accepted your review comment and change the code.
I resent for code review.

Thanks,
Raju.

On Tue, Oct 04, 2016 at 02:53:19PM +0200, Andrew Lunn wrote:
> EXTERNAL EMAIL
> 
> 
> > 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.
> 
> The double negative makes the code ugly. Plus a negative slowdown is a
> speed up! The kernel maintainability and sanity comes first, and if
> the data sheet is crazy, because it uses negative slows downs, it
> should be ignored. Get the data sheet fixed
> 
>Andrew

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

[Andrew Lunn]

> 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.

The double negative makes the code ugly. Plus a negative slowdown is a
speed up! The kernel maintainability and sanity comes first, and if
the data sheet is crazy, because it uses negative slows downs, it
should be ignored. Get the data sheet fixed

   Andrew

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

[Raju Lakkaraju]

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 
> >
> > 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 
> >
> > ---
> > 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

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

[Raju Lakkaraju]

From: Raju Lakkaraju 

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 

---
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 

---

 .../devicetree/bindings/net/mscc-phy-vsc8531.txt   |  3 ++-
 drivers/net/phy/mscc.c | 29 --
 include/dt-bindings/net/mscc-phy-vsc8531.h | 21 
 3 files changed, 18 insertions(+), 35 deletions(-)
 delete mode 100644 include/dt-bindings/net/mscc-phy-vsc8531.h

diff --git a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt 
b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
index 99c7eb0..241841c 100644
--- a/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
+++ b/Documentation/devicetree/bindings/net/mscc-phy-vsc8531.txt
@@ -18,7 +18,8 @@ Optional properties:
  to reprogram drive strength and in effect slow
  down the edge rate if desired.  Table 1 shows the
  impact to the edge rate per VDDMAC supply for each
- drive strength setting.
+ drive strength setting. VDDMAC supply voltage
+ should be one of the value in Table-1 first row.
  Ref: Table:1 - Edge rate change below.
 
 Note: see dt-bindings/net/mscc-phy-vsc8531.h for applicable values
diff --git a/drivers/net/phy/mscc.c b/drivers/net/phy/mscc.c
index a17573e..e25786e 100644
--- a/drivers/net/phy/mscc.c
+++ b/drivers/net/phy/mscc.c
@@ -12,7 +12,6 @@
 #include 
 #include 
 #include 
-#include 
 
 enum rgmii_rx_clock_delay {
RGMII_RX_CLK_DELAY_0_2_NS = 0,
@@ -56,12 +55,14 @@ enum rgmii_rx_clock_delay {
 #define PHY_ID_VSC8531   0x00070570
 #define PHY_ID_VSC8541   0x00070770
 
+#define MSCC_SLOWDOWN_MAX8
+
 struct edge_rate_table {
u16 vddmac;
int slowdown[MSCC_SLOWDOWN_MAX];
 };
 
-struct edge_rate_table edge_table[MSCC_VDDMAC_MAX] = {
+static const struct edge_rate_table edge_table[] = {
{3300, { 0, -2, -4,  -7,  -10, -17, -29, -53} },
{2500, { 0, -3, -6,  -10, -14, -23, -37, -63} },
{1800, { 0, -5, -9,  -16, -23, -35, -52, -76} },
@@ -81,18 +82,21 @@ static int vsc85xx_phy_page_set(struct phy_device *phydev, 
u8 page)
return rc;
 }
 
-static u8 edge_rate_magic_get(u16 vddmac,
- int slowdown)
+static u8 vsc85xx_edge_rate_magic_get(u16 vddmac,
+ int slowdown)
 {
-   int rc = (MSCC_SLOWDOWN_MAX - 1);
+   int rc = (ARRAY_SIZE(edge_table[0].slowdown) - 1);
u8 vdd;
u8 sd;
 
-   for (vdd = 0; vdd < MSCC_VDDMAC_MAX; vdd++) {
+   for (vdd = 0; vdd < ARRAY_SIZE(edge_table); vdd++) {
if (edge_table[vdd].vddmac == vddmac) {
-   for (sd = 0; sd < MSCC_SLOWDOWN_MAX; sd++) {
+   for (sd = 0;
+sd < ARRAY_SIZE(edge_table[0].slowdown);
+sd++) {
if (edge_table[vdd].slowdown[sd] <= slowdown) {
-   rc = (MSCC_SLOWDOWN_MAX - sd - 1);
+   rc = 

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

[Andrew Lunn]

On Tue, Oct 04, 2016 at 05:11:12PM +0530, Raju Lakkaraju wrote:
> From: Raju Lakkaraju 
> 
> 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 
> 
> ---
> 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