[PATCH] e1000: changed some expensive calls of udelay to usleep_range

[PATCH] e1000: changed some expensive calls of udelay to usleep_range

[nxf23276]

    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: nxf23276 <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..ee6ab53 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, 110);
 
 	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

Re: [PATCH] e1000: changed some expensive calls of udelay to usleep_range

[Jeff Kirsher]

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On Tue, 2017-08-22 at 16:02 -0500, nxf23276 wrote:
>     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: nxf23276 <matthew.tan_1@nxp.com>
> ---
>  drivers/net/ethernet/intel/e1000e/phy.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

First of all, your name is nxf23276?  Really??

Second, you titled your patch that you were makeding changes to e1000
driver, yet you are asking to modify e1000e.  Just based on these 2
needed changes, I am dropping your patch.

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