kernel: mac80211: add pending ath9k EEPROM swapping patches

There are two types of swapping the EEPROM data in the ath9k driver.
Before this series one type of swapping could not be used without the
other.

The first type of swapping looks at the "magic bytes" at the start of
the EEPROM data and performs swab16 on the EEPROM contents if needed.
The second type of swapping is EEPROM format specific and swaps
specific fields within the EEPROM itself (swab16, swab32 - depends on
the EEPROM format).

With this series the second part now looks at the EEPMISC register
inside the EEPROM, which uses a bit to indicate if the EEPROM data
is Big Endian (this is also done by the FreeBSD kernel).
This has a nice advantage: currently there are some out-of-tree hacks
(in OpenWrt and LEDE) where the EEPROM has a Big Endian header on a
Big Endian system (= no swab16 is performed) but the EEPROM itself
indicates that it's data is Little Endian. Until now the out-of-tree
code simply did a swab16 before passing the data to ath9k, so ath9k
first did the swab16 - this also enabled the format specific swapping.
These out-of-tree hacks are still working with the new logic, but it
is recommended to remove them. This implementation is based on a
discussion with Arnd Bergmann who raised concerns about the
robustness and portability of the swapping logic in the original OF
support patch review, see [0].

After a second round of patches (= v1 of this series) neither Arnd
Bergmann nor I were really happy with the complexity of the EEPROM
swapping logic. Based on a discussion (see [1] and [2]) we decided
that ath9k should use a defined format (specifying the endianness
of the data - I went with __le16 and __le32) when accessing the
EEPROM fields. A benefit of this is that we enable the EEPMISC based
swapping logic by default, just like the FreeBSD driver, see [3]. On
the devices which I have tested (see below) ath9k now works without
having to specify the "endian_check" field in ath9k_platform_data (or
a similar logic which could provide this via devicetree) as ath9k now
detects the endianness automatically. Only EEPROMs which are mangled
by some out-of-tree code still need the endian_check flag (or one can
simply remove that mangling from the out-of-tree code).

[0] http://www.spinics.net/lists/linux-wireless/msg152634.html
[1] https://marc.info/?l=linux-wireless&m=147250597503174&w=2
[2] https://marc.info/?l=linux-wireless&m=147254388611344&w=2
[3] https://github.com/freebsd/freebsd/blob/50719b56d9ce8d7d4beb53b16e9edb2e9a4a7a18/sys/dev/ath/ath_hal/ah_eeprom_9287.c#L351

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

1 files changed, 128 insertions, 0 deletions

diff --git a/package/kernel/mac80211/patches/555-ath9k-Make-the-EEPROM-swapping-check-use-the-eepmisc.patch b/package/kernel/mac80211/patches/555-ath9k-Make-the-EEPROM-swapping-check-use-the-eepmisc.patch
new file mode 100644
index 0000000000..3e3c2ea7a3
--- /dev/null
+++ b/package/kernel/mac80211/patches/555-ath9k-Make-the-EEPROM-swapping-check-use-the-eepmisc.patch
@@ -0,0 +1,128 @@
+From 1f796f9265c10384a274ac330f671ef4ac6d56e5 Mon Sep 17 00:00:00 2001
+From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
+Date: Mon, 3 Oct 2016 00:29:12 +0200
+Subject: [v2 PATCH 6/7] ath9k: Make the EEPROM swapping check use the eepmisc
+ register
+
+There are two ways of swapping the EEPROM data in the ath9k driver:
+1) swab16 based on the first two EEPROM "magic" bytes (same for all
+   EEPROM formats)
+2) field and EEPROM format specific swab16/swab32 (different for
+   eeprom_def, eeprom_4k and eeprom_9287)
+
+The result of the first check was used to also enable the second swap.
+This behavior seems incorrect, since the data may only be byte-swapped
+(afterwards the data could be in the correct endianness).
+Thus we introduce a separate check based on the "eepmisc" register
+(which is part of the EEPROM data). When bit 0 is set, then the EEPROM
+format specific values are in "big endian". This is also done by the
+FreeBSD kernel, see [0] for example.
+
+This allows us to parse EEPROMs with the "correct" magic bytes but
+swapped EEPROM format specific values. These EEPROMs (mostly found in
+lantiq and broadcom based big endian MIPS based devices) only worked
+due to platform specific "hacks" which swapped the EEPROM so the
+magic was inverted, which also enabled the format specific swapping.
+With this patch the old behavior is still supported, but neither
+recommended nor needed anymore.
+
+[0]
+https://github.com/freebsd/freebsd/blob/50719b56d9ce8d7d4beb53b16e9edb2e9a4a7a18/sys/dev/ath/ath_hal/ah_eeprom_9287.c#L351
+
+Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
+---
+ drivers/net/wireless/ath/ath9k/eeprom.c | 57 ++++++++++++++++++++++++---------
+ 1 file changed, 41 insertions(+), 16 deletions(-)
+
+--- a/drivers/net/wireless/ath/ath9k/eeprom.c
++++ b/drivers/net/wireless/ath/ath9k/eeprom.c
+@@ -155,11 +155,19 @@ bool ath9k_hw_nvram_read(struct ath_hw *
+ 	return ret;
+ }
+ 
++#ifdef __BIG_ENDIAN
++#define EXPECTED_EEPMISC_ENDIAN AR5416_EEPMISC_BIG_ENDIAN
++#else
++#define EXPECTED_EEPMISC_ENDIAN 0
++#endif
++
+ int ath9k_hw_nvram_swap_data(struct ath_hw *ah, bool *swap_needed, int size)
+ {
+ 	u16 magic;
+ 	u16 *eepdata;
++	u8 eepmisc;
+ 	int i;
++	bool needs_byteswap = false;
+ 	struct ath_common *common = ath9k_hw_common(ah);
+ 
+ 	if (!ath9k_hw_nvram_read(ah, AR5416_EEPROM_MAGIC_OFFSET, &magic)) {
+@@ -167,36 +175,53 @@ int ath9k_hw_nvram_swap_data(struct ath_
+ 		return -EIO;
+ 	}
+ 
+-	*swap_needed = false;
+ 	if (swab16(magic) == AR5416_EEPROM_MAGIC) {
++		needs_byteswap = true;
++		ath_dbg(common, EEPROM,
++			"EEPROM needs byte-swapping to correct endianness.\n");
++	} else if (magic != AR5416_EEPROM_MAGIC) {
++		if (ath9k_hw_use_flash(ah)) {
++			ath_dbg(common, EEPROM,
++				"Ignoring invalid EEPROM magic (0x%04x).\n",
++				magic);
++		} else {
++			ath_err(common,
++				"Invalid EEPROM magic (0x%04x).\n", magic);
++			return -EINVAL;
++		}
++	}
++
++	if (needs_byteswap) {
+ 		if (ah->ah_flags & AH_NO_EEP_SWAP) {
+ 			ath_info(common,
+ 				 "Ignoring endianness difference in EEPROM magic bytes.\n");
+ 		} else {
+-			*swap_needed = true;
+-		}
+-	} else if (magic != AR5416_EEPROM_MAGIC) {
+-		if (ath9k_hw_use_flash(ah))
+-			return 0;
++			eepdata = (u16 *)(&ah->eeprom);
+ 
+-		ath_err(common,
+-			"Invalid EEPROM Magic (0x%04x).\n", magic);
+-		return -EINVAL;
++			for (i = 0; i < size; i++)
++				eepdata[i] = swab16(eepdata[i]);
++		}
+ 	}
+ 
+-	eepdata = (u16 *)(&ah->eeprom);
+-
+-	if (*swap_needed) {
+-		ath_dbg(common, EEPROM,
+-			"EEPROM Endianness is not native.. Changing.\n");
++	*swap_needed = false;
+ 
+-		for (i = 0; i < size; i++)
+-			eepdata[i] = swab16(eepdata[i]);
++	eepmisc = ah->eep_ops->get_eepmisc(ah);
++	if ((eepmisc & AR5416_EEPMISC_BIG_ENDIAN) != EXPECTED_EEPMISC_ENDIAN) {
++		if (ah->ah_flags & AH_NO_EEP_SWAP) {
++			ath_info(common,
++				 "Ignoring endianness difference in eepmisc register.\n");
++		} else {
++			*swap_needed = true;
++			ath_dbg(common, EEPROM,
++				"EEPROM needs swapping according to the eepmisc register.\n");
++		}
+ 	}
+ 
+ 	return 0;
+ }
+ 
++#undef EXPECTED_EEPMISC_VAL
++
+ bool ath9k_hw_nvram_validate_checksum(struct ath_hw *ah, int size)
+ {
+ 	u32 i, sum = 0;