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ath9k: Avoid OF no-eeprom quirks when no qca,no-eeprom

Based on the process of discovery in
openwrt#1613, it has become clear
that (at least) the PowerCloud System CR5000 was unable to get
working 5GHz wireless (PCIe) because AH_USE_EEPROM was unconditionally
masked out, not only when qca,noeeprom was in the DTS.

This patch moves mask AH_USE_EEPROM into the if ... qca,noeeprom
OF test.

Thanks to Christian Lampartar (@chunkeey) for the heavy lifting and help.

Patch has been prepared for upstream and will be submitted after review
by @chunkeey and @xdarklight.

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>
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cshoredaniel authored and chunkeey committed Dec 17, 2018
1 parent f36bc3f commit 8d2a9e8027c96db8e932cd657a62013206c5755f
@@ -0,0 +1,73 @@
ath9k: Avoid OF no-EEPROM quirks without qca,no-eeprom

ath9k_of_init() function[0] was initially written on the assumption that
if someone had an explicit ath9k OF node that "there must be something
wrong, why would someone add an OF node if everything is fine"[1]
(Quoting Martin Blumenstingl)

"it turns out it's not that simple. with your requirements I'm now aware
of two use-cases where the current code in ath9k_of_init() doesn't work
without modifications"[1]

The "your requirements" Martin speaks of is the result of the fact that I
have a device (PowerCloud Systems CR5000) that uses the EEPROM for
caldata and firmware but for which the MAC address is take from the MTD
"art" partition[2], or more succinctly:

"some cards come with a physical EEPROM chip so "qca,no-eeprom" should not
be set (your use-case). in this case AH_USE_EEPROM should be set (which
is the default when there is no OF node)"[1]

The other use case is:

the firmware on some PowerMac G5 seems to add a OF node for the ath9k
card automatically. depending on the EEPROM on the card AH_NO_EEP_SWAP
should be unset (which is the default when there is no OF node). see [3]

After this patch to ath9k_of_init() the new behavior will be:

if there's no OF node then everything is the same as before
if there's an empty OF node then ath9k will use the hardware EEPROM
(before ath9k would fail to initialize because no EEPROM data was
provided by userspace)
if there's an OF node with only a MAC address then ath9k will use
the MAC address and the hardware EEPROM (see the case above)
with "qca,no-eeprom" EEPROM data from userspace will be requested.
the behavior here will not change
[1]

Martin provides additional background on EEPROM swapping[1] which I have
included in the patch annotation but not the commit message.

Thanks to Christian Lampartar <chunkeey@gmail.com> for all his help on
troubleshooting this issue and the basis for this patch.

Fixes: 138b41253d9c ("ath9k: parse the device configuration from an OF node")

[0]https://elixir.bootlin.com/linux/v4.20-rc7/source/drivers/net/wireless/ath/ath9k/init.c#L615
[1]https://github.com/openwrt/openwrt/pull/1645#issuecomment-448027058
[2]https://github.com/openwrt/openwrt/pull/1613
[3]https://patchwork.kernel.org/patch/10241731/

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>
--- a/drivers/net/wireless/ath/ath9k/init.c
+++ b/drivers/net/wireless/ath/ath9k/init.c
@@ -642,15 +642,15 @@ static int ath9k_of_init(struct ath_soft
ret = ath9k_eeprom_request(sc, eeprom_name);
if (ret)
return ret;
+
+ ah->ah_flags &= ~AH_USE_EEPROM;
+ ah->ah_flags |= AH_NO_EEP_SWAP;
}

mac = of_get_mac_address(np);
if (mac)
ether_addr_copy(common->macaddr, mac);

- ah->ah_flags &= ~AH_USE_EEPROM;
- ah->ah_flags |= AH_NO_EEP_SWAP;
-
return 0;
}

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