linux-kernel - [PATCH 3.13.y-ckt 061/143] iwlwifi: pcie: disable the SCD_BASE

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Date:	Tue, 31 Mar 2015 12:47:06 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13.y-ckt 061/143] iwlwifi: pcie: disable the SCD_BASE_ADDR when we resume from WoWLAN

3.13.11-ckt18 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Emmanuel Grumbach <emmanuel.grumbach@...el.com>

commit cd8f438405032ac8ff88bd8f2eca5e0c0063b14b upstream.

The base address of the scheduler in the device's memory
(SRAM) comes from two different sources. The periphery
register and the alive notification from the firmware.
We have a check in iwl_pcie_tx_start that ensures that
they are the same.
When we resume from WoWLAN, the firmware may have crashed
for whatever reason. In that case, the whole device may be
reset which means that the periphery register will hold a
meaningless value. When we come to compare
trans_pcie->scd_base_addr (which really holds the value we
had when we loaded the WoWLAN firmware upon suspend) and
the current value of the register, we don't see a match
unsurprisingly.
Trick the check to avoid a loud yet harmless WARN.
Note that when the WoWLAN has crashed, we will see that
in iwl_trans_pcie_d3_resume which will let the op_mode
know. Once the op_mode is informed that the WowLAN firmware
has crashed, it can't do much besides resetting the whole
device.

Reviewed-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@...el.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/net/wireless/iwlwifi/pcie/tx.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/iwlwifi/pcie/tx.c b/drivers/net/wireless/iwlwifi/pcie/tx.c
index 0adde91..d4654ba 100644
--- a/drivers/net/wireless/iwlwifi/pcie/tx.c
+++ b/drivers/net/wireless/iwlwifi/pcie/tx.c
@@ -729,7 +729,12 @@ void iwl_trans_pcie_tx_reset(struct iwl_trans *trans)
 	iwl_write_direct32(trans, FH_KW_MEM_ADDR_REG,
 			   trans_pcie->kw.dma >> 4);

-	iwl_pcie_tx_start(trans, trans_pcie->scd_base_addr);
+	/*
+	 * Send 0 as the scd_base_addr since the device may have be reset
+	 * while we were in WoWLAN in which case SCD_SRAM_BASE_ADDR will
+	 * contain garbage.
+	 */
+	iwl_pcie_tx_start(trans, 0);
 }

 /*
-- 
1.9.1

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