From: Akash Asthana <akashast@codeaurora.org>
To: Douglas Anderson <dianders@chromium.org>,
Wolfram Sang <wsa@the-dreams.de>
Cc: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
Rajendra Nayak <rnayak@codeaurora.org>,
swboyd@chromium.org, Alok Chauhan <alokc@codeaurora.org>,
Andy Gross <agross@kernel.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Girish Mahadevan <girishm@codeaurora.org>,
Karthikeyan Ramasubramanian <kramasub@codeaurora.org>,
Wolfram Sang <wsa@kernel.org>,
linux-arm-msm@vger.kernel.org, linux-i2c@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i2c: i2c-qcom-geni: Fix DMA transfer race
Date: Tue, 21 Jul 2020 16:18:23 +0530 [thread overview]
Message-ID: <fc39751a-c730-0181-6904-cca34ff0f62c@codeaurora.org> (raw)
In-Reply-To: <20200720172448.1.I7efdf6efaa6edadbb690196cd4fbe3392a582c89@changeid>
On 7/21/2020 5:54 AM, Douglas Anderson wrote:
> When I have KASAN enabled on my kernel and I start stressing the
> touchscreen my system tends to hang. The touchscreen is one of the
> only things that does a lot of big i2c transfers and ends up hitting
> the DMA paths in the geni i2c driver. It appears that KASAN adds
> enough delay in my system to tickle a race condition in the DMA setup
> code.
>
> When the system hangs, I found that it was running the geni_i2c_irq()
> over and over again. It had these:
>
> m_stat = 0x04000080
> rx_st = 0x30000011
> dm_tx_st = 0x00000000
> dm_rx_st = 0x00000000
> dma = 0x00000001
>
> Notably we're in DMA mode but are getting M_RX_IRQ_EN and
> M_RX_FIFO_WATERMARK_EN over and over again.
>
> Putting some traces in geni_i2c_rx_one_msg() showed that when we
> failed we were getting to the start of geni_i2c_rx_one_msg() but were
> never executing geni_se_rx_dma_prep().
>
> I believe that the problem here is that we are writing the transfer
> length and setting up the geni command before we run
> geni_se_rx_dma_prep(). If a transfer makes it far enough before we do
> that then we get into the state I have observed. Let's change the
> order, which seems to work fine.
>
> Fixes: 37692de5d523 ("i2c: i2c-qcom-geni: Add bus driver for the Qualcomm GENI I2C controller")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
Reviewed-by: Akash Asthana <akashast@codeaurora.org>
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,\na Linux Foundation Collaborative Project
prev parent reply other threads:[~2020-07-21 10:49 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 0:24 [PATCH] i2c: i2c-qcom-geni: Fix DMA transfer race Douglas Anderson
2020-07-21 5:37 ` Sai Prakash Ranjan
2020-07-21 5:59 ` Stephen Boyd
2020-07-21 7:07 ` Stephen Boyd
2020-07-21 10:58 ` Mukesh, Savaliya
2020-07-21 16:18 ` Doug Anderson
2020-07-21 18:55 ` Stephen Boyd
2020-07-21 20:26 ` Doug Anderson
2020-07-22 22:08 ` Doug Anderson
2020-07-21 10:48 ` Akash Asthana [this message]
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