linux-kernel - Re: [PATCH v1] nfc: pn544: Fix occasional HW initialization failure

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Message-ID: <7723e3ad-e004-a691-6605-50ce05132162@gmail.com>
Date:   Thu, 20 Feb 2020 00:41:56 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     sameo@...ux.intel.com, david@...t.cz, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] nfc: pn544: Fix occasional HW initialization failure

19.02.2020 22:11, David Miller пишет:
> From: Dmitry Osipenko <digetx@...il.com>
> Date: Wed, 19 Feb 2020 18:01:22 +0300
> 
>> 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>
> 
> Applied and queued up for -stable, thanks.
> 

Awesome, thanks!