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

Pavel Machek
2021-02-03T20:55:20Z

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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);

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