Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 0da6090f authored by Jesus Sanchez-Palencia's avatar Jesus Sanchez-Palencia Committed by Jeff Kirsher
Browse files

igb: Clarify idleslope config constraints 



By design, the idleslope increments are restricted to 16.384kbps steps.
Add a comment to igb_main.c making that explicit and add one example
that illustrates the impact of that.

Signed-off-by: default avatarJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Tested-by: default avatarAaron Brown <aaron.f.brown@intel.com>
Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
parent b701cacd

drivers/net/ethernet/intel/igb/igb_main.c

+14 −0
Original line number Diff line number Diff line
@@ -1744,6 +1744,20 @@ static void igb_configure_cbs(struct igb_adapter *adapter, int queue, 
		 *     value = idleSlope * 61034

		 *             -----------------                          (E6)

		 *                  1000000

		 *

		 * NOTE: For i210, given the above, we can see that idleslope

		 *       is represented in 16.38431 kbps units by the value at

		 *       the TQAVCC register (1Gbps / 61034), which reduces

		 *       the granularity for idleslope increments.

		 *       For instance, if you want to configure a 2576kbps

		 *       idleslope, the value to be written on the register

		 *       would have to be 157.23. If rounded down, you end

		 *       up with less bandwidth available than originally

		 *       required (~2572 kbps). If rounded up, you end up

		 *       with a higher bandwidth (~2589 kbps). Below the

		 *       approach we take is to always round up the

		 *       calculated value, so the resulting bandwidth might

		 *       be slightly higher for some configurations.

		 */

		value = DIV_ROUND_UP_ULL(idleslope * 61034ULL, 1000000);