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[79.139.233.37]) by smtp.googlemail.com with ESMTPSA id m24sm546736ljb.81.2020.02.19.13.41.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Feb 2020 13:41:57 -0800 (PST) Subject: Re: [PATCH v1] nfc: pn544: Fix occasional HW initialization failure To: David Miller Cc: sameo@linux.intel.com, david@ixit.cz, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200219150122.31524-1-digetx@gmail.com> <20200219.111130.5189327548859835.davem@davemloft.net> From: Dmitry Osipenko Message-ID: <7723e3ad-e004-a691-6605-50ce05132162@gmail.com> Date: Thu, 20 Feb 2020 00:41:56 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <20200219.111130.5189327548859835.davem@davemloft.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 19.02.2020 22:11, David Miller пишет: > From: Dmitry Osipenko > 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 > > Applied and queued up for -stable, thanks. > Awesome, thanks!