netdev - long delays in rtl8723 drivers in irq disabled sections

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Date:   Tue, 12 Nov 2019 22:02:25 +0100
From:   Lucas Stach <dev@...xeye.de>
To:     wlanfae@...ltek.com, Ping-Ke Shih <pkshih@...ltek.com>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: long delays in rtl8723 drivers in irq disabled sections

Hi all,

while investigating some latency issues on my laptop I stumbled across
quite large delays in the rtl8723 PHY code, which are done in IRQ
disabled atomic sections, which is blocking IRQ servicing for all
devices in the system.

Specifically there are 3 consecutive 1ms delays in
rtl8723_phy_rf_serial_read(), which is used in an IRQ disabled call
path. Sadly those delays don't have any comment in the code explaining
why they are needed. I hope that anyone can tell if those delays are
strictly neccessary and if so if they really need to be this long.

Regards,
Lucas