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由 Luis R. Rodriguez 提交于
Atheros single stream AR9285 and AR9271 have half the PCU TX FIFO buffer size of that of dual stream devices. Dual stream devices have a max PCU TX FIFO size of 8 KB while single stream devices have 4 KB. Single stream devices have an issue though and require hardware only to use half of the amount of its capable PCU TX FIFO size, 2 KB and this requires a change in software. Technically a change would not have been required (except for frame burst considerations of 128 bytes) if these devices would have been able to use the full 4 KB of the PCU TX FIFO size but our systems engineers recommend 2 KB to be used only. We enforce this through software by reducing the max frame triggger level to 2 KB. Fixing the max frame trigger level should then have a few benefits: * The PER will now be adjusted as designed for underruns when the max trigger level is reached. This should help alleviate the bus as the rate control algorithm chooses a slower rate which should ensure frames are transmitted properly under high system bus load. * The poll we use on our TX queues should now trigger and work as designed for single stream devices. The hardware passes data from each TX queue on the PCU TX FIFO queue respecting each queue's priority. The new trigger level ensures this seeding of the PCU TX FIFO queue occurs as designed which could mean avoiding false resets and actually reseting hw correctly when a TX queue is indeed stuck. * Some undocumented / unsupported behaviour could have been triggered when the max trigger level level was being set to 4 KB on single stream devices. Its not clear what this issue was to me yet. Cc: Kyungwan Nam <kyungwan.nam@atheros.com> Cc: Bennyam Malavazi <bennyam.malavazi@atheros.com> Cc: Stephen Chen <stephen.chen@atheros.com> Cc: Shan Palanisamy <shan.palanisamy@atheros.com> Cc: Paul Shaw <paul.shaw@atheros.com> Signed-off-by: NVasanthakumar Thiagarajan <vasanth@atheros.com> Signed-off-by: NLuis R. Rodriguez <lrodriguez@atheros.com> Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>
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