From: "Mukesh, Savaliya" <msavaliy@codeaurora.org>
To: Stephen Boyd <swboyd@chromium.org>,
Douglas Anderson <dianders@chromium.org>,
Wolfram Sang <wsa@the-dreams.de>
Cc: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
Akash Asthana <akashast@codeaurora.org>,
Rajendra Nayak <rnayak@codeaurora.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>,
Sagar Dharia <sdharia@codeaurora.org>,
linux-arm-msm@vger.kernel.org, linux-i2c@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] i2c: i2c-qcom-geni: Fix DMA transfer race
Date: Thu, 23 Jul 2020 11:46:28 +0530 [thread overview]
Message-ID: <bb8b1e99-2f55-910c-c37f-5e0fef0fb4b1@codeaurora.org> (raw)
In-Reply-To: <159546541191.3847286.3212989047313785097@swboyd.mtv.corp.google.com>
On 7/23/2020 6:20 AM, Stephen Boyd wrote:
> Quoting Douglas Anderson (2020-07-22 15:00:21)
>> 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 starting 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.
>>
>> Although problems were seen on the RX path, code inspection suggests
>> that the TX should be changed too. Change it as well.
>>
>> Fixes: 37692de5d523 ("i2c: i2c-qcom-geni: Add bus driver for the Qualcomm GENI I2C controller")
>> Signed-off-by: Douglas Anderson <dianders@chromium.org>
>> Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
>> Reviewed-by: Akash Asthana <akashast@codeaurora.org>
Reviewed-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>
>> ---
> Reviewed-by: Stephen Boyd <swboyd@chromium.org>
next prev parent reply other threads:[~2020-07-23 6:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 22:00 [PATCH v2] i2c: i2c-qcom-geni: Fix DMA transfer race Douglas Anderson
2020-07-23 0:50 ` Stephen Boyd
2020-07-23 6:16 ` Mukesh, Savaliya [this message]
2020-07-23 19:56 ` Wolfram Sang
2020-07-26 12:47 ` Wolfram Sang
2020-07-27 8:36 ` Akash Asthana
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