linux-kernel - RE: [PATCH V8 3/5] i2c: tegra: Add DMA Support

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Date:   Thu, 31 Jan 2019 16:56:56 +0000
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mantravadi Karthik <mkarthik@...dia.com>,
        Shardar Mohammed <smohammed@...dia.com>,
        Timo Alho <talho@...dia.com>
CC:     "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Subject: RE: [PATCH V8 3/5] i2c: tegra: Add DMA Support


> >>  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.