linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH] e1000e: changed some expensive calls of udelay to usleep_range
@ 2017-08-23 15:59 Matthew Tan
  2017-08-29  7:19 ` [Intel-wired-lan] " Neftin, Sasha
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Matthew Tan @ 2017-08-23 15:59 UTC (permalink / raw)
  To: jeffrey.t.kirsher
  Cc: michael.kardonik, carolyn.wyborny, donald.c.skidmore,
	bruce.w.allan, john.ronciak, mitch.a.williams, intel-wired-lan,
	netdev, linux-kernel, Matthew Tan

    Calls to udelay are not preemtable by userspace so userspace
    applications experience a large (~200us) latency when running on core
    0. Instead usleep_range can be used to be more friendly to userspace
    since it is preemtable. This is due to udelay using busy-wait loops
    while usleep_rang uses hrtimers instead. It is recommended to use
    udelay when the delay is <10us since at that precision overhead of
    usleep_range hrtimer setup causes issues. However, the replaced calls
    are for 50us and 100us so this should not be not an issue.

Signed-off-by: Matthew Tan <matthew.tan_1@nxp.com>
---
 drivers/net/ethernet/intel/e1000e/phy.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/phy.c b/drivers/net/ethernet/intel/e1000e/phy.c
index de13aea..e318fdc 100644
--- a/drivers/net/ethernet/intel/e1000e/phy.c
+++ b/drivers/net/ethernet/intel/e1000e/phy.c
@@ -158,7 +158,7 @@ s32 e1000e_read_phy_reg_mdic(struct e1000_hw *hw, u32 offset, u16 *data)
 	 * the lower time out
 	 */
 	for (i = 0; i < (E1000_GEN_POLL_TIMEOUT * 3); i++) {
-		udelay(50);
+		usleep_range(40, 60);
 		mdic = er32(MDIC);
 		if (mdic & E1000_MDIC_READY)
 			break;
@@ -183,7 +183,7 @@ s32 e1000e_read_phy_reg_mdic(struct e1000_hw *hw, u32 offset, u16 *data)
 	 * reading duplicate data in the next MDIC transaction.
 	 */
 	if (hw->mac.type == e1000_pch2lan)
-		udelay(100);
+		usleep_range(90, 100);
 
 	return 0;
 }
@@ -222,7 +222,7 @@ s32 e1000e_write_phy_reg_mdic(struct e1000_hw *hw, u32 offset, u16 data)
 	 * the lower time out
 	 */
 	for (i = 0; i < (E1000_GEN_POLL_TIMEOUT * 3); i++) {
-		udelay(50);
+		usleep_range(40, 60);
 		mdic = er32(MDIC);
 		if (mdic & E1000_MDIC_READY)
 			break;
@@ -246,7 +246,7 @@ s32 e1000e_write_phy_reg_mdic(struct e1000_hw *hw, u32 offset, u16 data)
 	 * reading duplicate data in the next MDIC transaction.
 	 */
 	if (hw->mac.type == e1000_pch2lan)
-		udelay(100);
+		usleep_range(90, 110);
 
 	return 0;
 }
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-09-08  9:28 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-08-23 15:59 [PATCH] e1000e: changed some expensive calls of udelay to usleep_range Matthew Tan
2017-08-29  7:19 ` [Intel-wired-lan] " Neftin, Sasha
2017-09-04 16:25 ` Pavel Machek
2017-09-07 22:19   ` [Intel-wired-lan] " Brown, Aaron F
2017-09-08  9:28     ` Pavel Machek
2017-09-04 16:36 ` Paul Menzel

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).