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[91.79.175.49]) by smtp.googlemail.com with ESMTPSA id 85-v6sm897764lja.16.2019.01.31.09.38.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 31 Jan 2019 09:38:30 -0800 (PST) Subject: Re: [PATCH V8 3/5] i2c: tegra: Add DMA Support From: Dmitry Osipenko To: Sowjanya Komatineni , "thierry.reding@gmail.com" , Jonathan Hunter , Mantravadi Karthik , Shardar Mohammed , Timo Alho Cc: "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-i2c@vger.kernel.org" References: <1548915387-28826-1-git-send-email-skomatineni@nvidia.com> <1548915387-28826-3-git-send-email-skomatineni@nvidia.com> <4663c7b9-d306-1cd4-1bdc-f7be84af0667@gmail.com> <8a88f8ee-24d3-00ac-f1fa-c43b576ed82c@gmail.com> Message-ID: Date: Thu, 31 Jan 2019 20:38:29 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: 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 31.01.2019 20:25, Dmitry Osipenko пишет: > 31.01.2019 20:11, Dmitry Osipenko пишет: >> 31.01.2019 19:56, Sowjanya Komatineni пишет: >>> >>>>>> drivers/i2c/busses/Kconfig | 2 +- >>>>>> drivers/i2c/busses/i2c-tegra.c | 362 >>>>>> ++++++++++++++++++++++++++++++++++++++--- >>>>>> 2 files changed, 339 insertions(+), 25 deletions(-) >>>>> >>>>> Tegra20 crashes because of this patch: >>>>> >>>> [snip] >>>>> <4>[ 3.395915] ------------[ cut here ]------------ >>>>> <2>[ 3.395919] kernel BUG at drivers/i2c/busses/i2c-tegra.c:810! >>>> The BUG line is from: >>>> >>>> if (status & I2C_INT_PACKET_XFER_COMPLETE) { >>>> if (i2c_dev->is_curr_dma_xfer) >>>> i2c_dev->msg_buf_remaining = 0; >>>> BUG_ON(i2c_dev->msg_buf_remaining); >>>> complete(&i2c_dev->msg_complete); >>>> } >>>> >>> BUG_ON line is not part of this change. It was already there in existing driver. >>> Based on log, I see DMA transfer is done for 224 bytes followed by 1 successful PIO transfer and then on next PIO transfer it received packet xfer complete interrupt with incomplete transfer bytes and that where it hit BUG_ON condition. >>> >>> >> >> Yes, that BUG_ON is caused by the DMA transferring. Everything works fine be setting dma=false in the code, hence it's likely not a bug in the code (at least for now it looks fine), but likely that HW is not programmed correctly. >> > > It works with this change: > > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c > index fe5b89abc576..8e059e94b94e 100644 > --- a/drivers/i2c/busses/i2c-tegra.c > +++ b/drivers/i2c/busses/i2c-tegra.c > @@ -1170,10 +1170,11 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev, > time_left, completion_done(&i2c_dev->msg_complete), > i2c_dev->msg_err); > > + tegra_i2c_init(i2c_dev, true); > + > if (likely(i2c_dev->msg_err == I2C_ERR_NONE)) > return 0; > > - tegra_i2c_init(i2c_dev, true); > /* start recovery upon arbitration loss in single master mode */ > if (i2c_dev->msg_err == I2C_ERR_ARBITRATION_LOST) { > if (!i2c_dev->is_multimaster_mode) > > > Which means that HW state is kept dirty after DMA transfer. Please check everything carefully. > Also, enforcing dma=true regardless of transfer size doesn't work as well.