From c3331d2fe3fd4d5e321f2467d01f72de7edfb5d0 Mon Sep 17 00:00:00 2001 From: Dmitry Osipenko Date: Wed, 19 Feb 2020 18:01:22 +0300 Subject: [PATCH] nfc: pn544: Fix occasional HW initialization failure 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 Signed-off-by: David S. Miller --- drivers/nfc/pn544/i2c.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/nfc/pn544/i2c.c b/drivers/nfc/pn544/i2c.c index 720c89d6066e..4ac8cb262559 100644 --- a/drivers/nfc/pn544/i2c.c +++ b/drivers/nfc/pn544/i2c.c @@ -225,6 +225,7 @@ static void pn544_hci_i2c_platform_init(struct pn544_i2c_phy *phy) out: gpiod_set_value_cansleep(phy->gpiod_en, !phy->en_polarity); + usleep_range(10000, 15000); } static void pn544_hci_i2c_enable_mode(struct pn544_i2c_phy *phy, int run_mode) -- 2.30.2