nfc: pn544: Fix occasional HW initialization failure
authorDmitry Osipenko <digetx@gmail.com>
Wed, 19 Feb 2020 15:01:22 +0000 (18:01 +0300)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 5 Mar 2020 15:42:16 +0000 (16:42 +0100)
commitbee419ec70d957f01aa7d634b1fe4a2dda44ab53
treecf97408e1963d9bd8d0a1f581b0ea35e07dc8a9f
parent24b0fc7c2913759176ad0b41eacad539c08a7d64
nfc: pn544: Fix occasional HW initialization failure

[ Upstream commit c3331d2fe3fd4d5e321f2467d01f72de7edfb5d0 ]

The PN544 driver checks the "enable" polarity during of driver's probe and
it's doing that by turning ON and OFF NFC with different polarities until
enabling succeeds. It takes some time for the hardware to power-down, and
thus, to deassert the IRQ that is raised by turning ON the hardware.
Since the delay after last power-down of the polarity-checking process is
missed in the code, the interrupt may trigger immediately after installing
the IRQ handler (right after the checking is done), which results in IRQ
handler trying to touch the disabled HW and ends with marking NFC as
'DEAD' during of the driver's probe:

  pn544_hci_i2c 1-002a: NFC: nfc_en polarity : active high
  pn544_hci_i2c 1-002a: NFC: invalid len byte
  shdlc: llc_shdlc_recv_frame: NULL Frame -> link is dead

This patch fixes the occasional NFC initialization failure on Nexus 7
device.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/nfc/pn544/i2c.c