[OpenWrt-Devel] Pending ath79 issues on ar9342 and 4.14/4.19 kernels

Petr Štetiar ynezz at true.cz
Thu Jan 10 03:21:24 EST 2019

Petr Štetiar <ynezz at true.cz> [2019-01-02 01:24:22]:

> 1. MAC reset issue
>  While converting UBNT Nanostation M XW to ath79, I've found out, that the MAC
>  isn't properly reset on ath79, resulting in disfunctional networking due to
>  MAC_CFG2_CRC_EN bit set in AG71XX_REG_MAC_CFG2. My first naive attempt to fix
>  this issue[A], but I wasn't satisfied with this fix it so I've asked for help
>  with proper fix.
>  With the help of blogic/Guo I've found out, that we need to reset MDIO/GMAC in
>  one step, otherwise resetting of MAC doesn't work. ar71xx does this, but ath79
>  doesn't, in ath79 we reset MDIO and GMAC separately. I'm able to reset MAC
>  properly in ath79 with following changes:
>   &eth0 {
>     reset-names = "mac", "mdio";
>     resets = <&rst 9>, <&rst 22>;
>   };
>  and using `devm_reset_control_array_get_exclusive` to reset the MAC. But then
>  there's issue with MDIO configuration, since MDIO is configured/probed before
>  MAC reset and issue with fast reset as well, since on ar71xx it's only
>  reseting GMAC0 (bit 9) so it needs someone with better complete picture to fix
>  it properly.

Seems to be fixed in https://github.com/openwrt/openwrt/pull/1735

> 2. Different MDIO divider values
>  I've observed this on UBNT Bullet M XW.  On ar71xx it's using
>  MII_CFG_CLK_DIV_58 fallback value because ag71xx_mdio_get_divider() doesn't
>  return anything, but on ath79 it's using MII_CFG_CLK_DIV_50 as computed in
>  ag71xx_mdio_get_divider(). I'm not sure if it has significant impact on
>  anything.

Still unsure about this one.

> 3. TX hang workaround is not enabled (DMA engine stuck)
>  On ath79 we enable this workaround only for `qca,ar7240-eth`, but in ar71xx
>  it's enabled for is_ar724x SoCs (ar724x, ar933x, ar934x, qca9533, tp9343,
>  qca955x, qca956x). What is correct? To me it seems, that we should enable it
>  for same set of SoCs in ath79 as well, but I'm not 100% sure.

Still unsure about this one, but proposed fix in https://patchwork.ozlabs.org/patch/1020748/

> 4. Transmit queue 0 timed out
>  On ath79 and UBNT Bullet M XW I'm experiencing weird issues during network
>  setup[B] which I'm able to reproduce easily with following commands:
>   uci set network.lan.ipaddr=''
>   uci commit network
>   ifup lan
>  Resulting after some time in:
>   ...
>   WARNING: CPU: 0 PID: 0 at net/sched/sch_generic.c:461 dev_watchdog+0x16c/0x280
>   NETDEV WATCHDOG: eth0 (ag71xx): transmit queue 0 timed out
>   ...
>  Sometimes I'm not able to use networking anymore, sometimes it's enough to
>  just ifdown/ifup lan and the network is backup.
>  While trying to fix this issue, I've found out about 2. and 3., but fixing
>  them in the same way as on ar71xx doesn't help with this issue. Proper MAC
>  reset as described in 1. doesn't help with this issue either.
>  Any idea what might possibly cause this? Dump of registers looks same on
>  ar71xx/ath79 so it's probably something related to code path changes.

Seems to be fixed in https://patchwork.ozlabs.org/patch/1020158/

-- ynezz

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