linux-kernel - [PATCH 4.4 17/72] nfc: pn544: Fix occasional HW initialization failure

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Message-Id: <20200310123605.849507429@linuxfoundation.org>
Date:   Tue, 10 Mar 2020 13:38:30 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dmitry Osipenko <digetx@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 17/72] nfc: pn544: Fix occasional HW initialization failure

From: Dmitry Osipenko <digetx@...il.com>

[ 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@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/nfc/pn544/i2c.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/nfc/pn544/i2c.c
+++ b/drivers/nfc/pn544/i2c.c
@@ -241,6 +241,7 @@ static void pn544_hci_i2c_platform_init(

 out:
 	gpio_set_value_cansleep(phy->gpio_en, !phy->en_polarity);
+	usleep_range(10000, 15000);
 }

 static void pn544_hci_i2c_enable_mode(struct pn544_i2c_phy *phy, int run_mode)