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ath9k: implement IO serialization

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All 802.11n PCI devices (Cardbus, PCI, mini-PCI) require
serialization of IO when on non-uniprocessor systems. PCI
express devices not not require this.

This should fix our only last standing open ath9k kernel.org
bugzilla bug report:

http://bugzilla.kernel.org/show_bug.cgi?id=12110

A port is probably required to older kernels and I can work on
that.

Cc: stable@kernel.org
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Luis R. Rodriguez
2009-03-12 18:18:49 -04:00
committed by John W. Linville
parent 6f16bf3bdb
commit 6158425be3
4 changed files with 55 additions and 2 deletions
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19
drivers/net/wireless/ath9k/hw.c
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@@ -437,6 +437,25 @@ static void ath9k_hw_set_defaults(struct ath_hal *ah)
}
ah->ah_config.intr_mitigation = 1;
/*
* We need this for PCI devices only (Cardbus, PCI, miniPCI)
* _and_ if on non-uniprocessor systems (Multiprocessor/HT).
* This means we use it for all AR5416 devices, and the few
* minor PCI AR9280 devices out there.
*
* Serialization is required because these devices do not handle
* well the case of two concurrent reads/writes due to the latency
* involved. During one read/write another read/write can be issued
* on another CPU while the previous read/write may still be working
* on our hardware, if we hit this case the hardware poops in a loop.
* We prevent this by serializing reads and writes.
*
* This issue is not present on PCI-Express devices or pre-AR5416
* devices (legacy, 802.11abg).
*/
if (num_possible_cpus() > 1)
ah->ah_config.serialize_regmode = SER_REG_MODE_AUTO;
}
static struct ath_hal_5416 *ath9k_hw_newstate(u16 devid,