diff mbox series

[4.19,26/37] iwlwifi: pcie: use jiffies for memory read spin time limit

Message ID 20210202132944.017286490@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman Feb. 2, 2021, 1:39 p.m. UTC 
From: Johannes Berg <johannes.berg@intel.com>

[ Upstream commit 6701317476bbfb1f341aa935ddf75eb73af784f9 ]

There's no reason to use ktime_get() since we don't need any better
precision than jiffies, and since we no longer disable interrupts
around this code (when grabbing NIC access), jiffies will work fine.
Use jiffies instead of ktime_get().

This cleanup is preparation for the following patch "iwlwifi: pcie: reschedule
in long-running memory reads". The code gets simpler with the weird clock use
etc. removed before we add cond_resched().

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20210115130253.621c948b1fad.I3ee9f4bc4e74a0c9125d42fb7c35cd80df4698a1@changeid
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/wireless/intel/iwlwifi/pcie/trans.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

Comments

Pavel Machek Feb. 3, 2021, 8:42 p.m. UTC | #1 
Hi!

> From: Johannes Berg <johannes.berg@intel.com>

> 

> [ Upstream commit 6701317476bbfb1f341aa935ddf75eb73af784f9 ]

> 

> There's no reason to use ktime_get() since we don't need any better

> precision than jiffies, and since we no longer disable interrupts

> around this code (when grabbing NIC access), jiffies will work fine.

> Use jiffies instead of ktime_get().

> 

> This cleanup is preparation for the following patch "iwlwifi: pcie: reschedule

> in long-running memory reads". The code gets simpler with the weird clock use

> etc. removed before we add cond_resched().


As far as I can tell, this is not really suitable for v4.19 (and
probably others), as we still disable interrupts in
iwl_trans_pcie_release_nic_access() in 4.19.

Best regards,
								Pavel
								

> @@ -2137,11 +2137,7 @@ static int iwl_trans_pcie_read_mem(struct iwl_trans *trans, u32 addr,

>  							HBUS_TARG_MEM_RDAT);

>  				offs++;

>  

> -				/* calling ktime_get is expensive so

> -				 * do it once in 128 reads

> -				 */

> -				if (offs % 128 == 0 && ktime_after(ktime_get(),

> -								   timeout))

> +				if (time_after(jiffies, end))

>  					break;

>  			}

>  			iwl_trans_release_nic_access(trans, &flags);


-- 
http://www.livejournal.com/~pavelmachek
diff mbox series

Patch

diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
index f48c7cac122e9..fe772b716a8df 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
@@ -2126,7 +2126,7 @@  static int iwl_trans_pcie_read_mem(struct iwl_trans *trans, u32 addr,
 
 	while (offs < dwords) {
 		/* limit the time we spin here under lock to 1/2s */
-		ktime_t timeout = ktime_add_us(ktime_get(), 500 * USEC_PER_MSEC);
+		unsigned long end = jiffies + HZ / 2;
 
 		if (iwl_trans_grab_nic_access(trans, &flags)) {
 			iwl_write32(trans, HBUS_TARG_MEM_RADDR,
@@ -2137,11 +2137,7 @@  static int iwl_trans_pcie_read_mem(struct iwl_trans *trans, u32 addr,
 							HBUS_TARG_MEM_RDAT);
 				offs++;
 
-				/* calling ktime_get is expensive so
-				 * do it once in 128 reads
-				 */
-				if (offs % 128 == 0 && ktime_after(ktime_get(),
-								   timeout))
+				if (time_after(jiffies, end))
 					break;
 			}
 			iwl_trans_release_nic_access(trans, &flags);