Re: [PATCH 2/2 net-next] net: stmmac: Improve documentation on AVB parameters

Hi Peppe,

Às 8:09 AM de 7/7/2017, Giuseppe CAVALLARO escreveu:

Hi Joao

On 7/5/2017 12:34 PM, Joao Pinto wrote:

quoted

Hi Peppe,

Às 8:10 AM de 6/9/2017, Giuseppe CAVALLARO escreveu:

quoted

Hi Joao

On 6/8/2017 8:02 PM, Joao Pinto wrote:

quoted

This patch fixes the description of the DT AVB parameters and gives
an accurate example. It was also included the base values that were
used to get the example' CBS paremeter values.

Signed-off-by: Joao Pinto<redacted>
---
   Documentation/devicetree/bindings/net/stmmac.txt | 24 ++++++++++++++++--------
   1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/stmmac.txt

b/Documentation/devicetree/bindings/net/stmmac.txt
index c3a7be6..707426d 100644

--- a/Documentation/devicetree/bindings/net/stmmac.txt
+++ b/Documentation/devicetree/bindings/net/stmmac.txt

@@ -109,10 +109,10 @@ Optional properties:
                 [Attention] Queue 0 is reserved for legacy traffic
                 and so no AVB is available in this queue.
           - Configure Credit Base Shaper (if AVB Mode selected):
-            - snps,send_slope: enable Low Power Interface
-            - snps,idle_slope: unlock on WoL
-            - snps,high_credit: max write outstanding req. limit
-            - snps,low_credit: max read outstanding req. limit
+            - snps,send_slope: Send Slope Credit value
+            - snps,idle_slope:  Idle Slope Credit value
+            - snps,high_credit: High Credit value
+            - snps,low_credit: Low Credit value
           - snps,priority: TX queue priority (Range: 0x0 to 0xF)
   Examples:
   @@ -143,10 +143,18 @@ Examples:
             queue1 {
               snps,avb-algorithm;
-            snps,send_slope = <0x1000>;
-            snps,idle_slope = <0x1000>;
-            snps,high_credit = <0x3E800>;
-            snps,low_credit = <0xFFC18000>;
+            /*
+             *  Example AVB parameters based on:
+             *   Allocated Bandwidth: 40%
+             *   Maximum Frame size: 1000 bytes
+             *   Maximum Interference size: 1500 bytes
+             *   Port Transmit Rate: 8
+             *   Scaling Factor: 1024
+             */
+            snps,idle_slope = <0xCCC>;
+            snps,send_slope = <0x1333>;
+            snps,high_credit = <0x4B0000>;

Thanks for having taken care about this changes, please, as required, add a
cover-letter
and give more information about these values that can be tuned by user and, for
example,
the snps,high_credit could be as default = 0xbe4000 that is a reasonable value
because
comes from 1522 * 8 * 1024 and LOW credit is the two complement.
                       ^^^^^
                     frame size ---> maximum is 16

I calculate the hi credit this way:

   HiCredit = BW / 100 * MaxInterferenceSize * 8 * Scaling

Can I assume that you are considering 100% bandwidth for this example channel?
If so, it is not correct, since the maximum bandwidth should be 75%, leaving at
least 25% for default channel 0 (I think this is assured in the hardware).

ok, I did not remember that so I let you detail with a right example this part 
in the doc.

Well done and thanks.

No problem! I will send an example soon. Thanks.

Joao

Peppe

quoted

Thanks,
Joao

quoted

Regards
Peppe

quoted

+            snps,low_credit = <0xFFB50000>;
               snps,priority = <0x1>;
           };
       };