Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx> writes: > Hello Kalle, > > On Fri, Nov 25, 2016 at 4:06 PM, Valo, Kalle <kvalo@xxxxxxxxxxxxxxxx> wrote: >> Kalle Valo <kvalo@xxxxxxxxxxxxxx> writes: >> >>> Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx> writes: >>> >>>> 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). >>>> >>>> Testing: >>>> - tested by myself on AR9287 with Big Endian EEPROM >>>> - tested by myself on AR9227 with Little Endian EEPROM >>>> - tested by myself on AR9381 (using the ar9003_eeprom implementation, >>>> which did not suffer from this whole problem) >>>> - how do we proceed with testing? maybe we could keep this in a >>>> feature-branch and add these patches to LEDE once we have an ACK to >>>> get more people to test this >>>> >>>> This series depends on my other series (v7): >>>> "add devicetree support to ath9k" - see [4] >>> >>> I think this looks pretty good. If there's a bug somewhere it should be >>> quite easy to fix so I'm not that worried and would be willing to take >>> these as soon as I have applied the dependency series. IIRC your >>> devicetree patches will have at least one more review round so that will >>> take some time still. In the meantime it would be great if LEDE folks >>> could take a look at these and comment (or test). >> >> So are everyone happy with this? I haven't seen any comments. If I don't >> here anything I'm planning to take these, most likely for 4.11. > > the patches have been in LEDE for almost two weeks now and I did not > see any reports of ath9k breakage (footnote below). > > It seems that there are a few devices out there where the whole EEPROM > is swab16'ed which switches the position of the 1-byte fields > opCapFlags and eepMisc. > those still work fine with the new code, however I had a second patch > in LEDE [0] which results in ath9k_platform_data.endian_check NOT > being set anymore. > that endian_check flag was used before to swab16 the whole EEPROM, to > correct the position of the 1-byte fields again. > Currently we are fixing this in the firmware hotplug script: [1] > This is definitely not a blocker for this series though (if we want to > have a devicetree replacement for "ath9k_platform_data.endian_check" > then I'd work on that within a separate series, but I somewhat > consider these EEPROMs as "broken" so fixing them in > userspace/firmware hotplug script is fine for me) Sounds good to me, thanks for the thorough followup. I'm planning to apply these any day. -- Kalle Valo
