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Date:   Fri, 28 Aug 2020 17:16:08 +0530
From:   rojay@codeaurora.org
To:     Stephen Boyd <swboyd@chromium.org>
Cc:     wsa@kernel.org, dianders@chromium.org,
        saiprakash.ranjan@codeaurora.org, gregkh@linuxfoundation.org,
        mka@chromium.org, akashast@codeaurora.org,
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        rnayak@codeaurora.org, agross@kernel.org,
        bjorn.andersson@linaro.org, linux-arm-msm@vger.kernel.org,
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        sumit.semwal@linaro.org, linux-media@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org
Subject: Re: [PATCH V2 2/2] i2c: i2c-qcom-geni: Add shutdown callback for i2c
In-Reply-To: <159796935923.334488.7479152222902825306@swboyd.mtv.corp.google.com>
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 <20200820103522.26242-3-rojay@codeaurora.org>
 <159796935923.334488.7479152222902825306@swboyd.mtv.corp.google.com>
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On 2020-08-21 05:52, Stephen Boyd wrote:
> Quoting Roja Rani Yarubandi (2020-08-20 03:35:22)
>> If the hardware is still accessing memory after SMMU translation
>> is disabled (as part of smmu shutdown callback), then the
>> IOVAs (I/O virtual address) which it was using will go on the bus
>> as the physical addresses which will result in unknown crashes
>> like NoC/interconnect errors.
>> 
>> So, implement shutdown callback to i2c driver to unmap DMA mappings
>> during system "reboot" or "shutdown".
>> 
>> Signed-off-by: Roja Rani Yarubandi <rojay@codeaurora.org>
>> ---
> 
> I'd still put a Fixes tag because it's fixing the driver when someone
> runs shutdown.
> 

Okay, will add fixes tag.

>> Changes in V2:
>>  - As per Stephen's comments added seperate function for stop 
>> transfer,
>>    fixed minor nitpicks.
>> 
>>  drivers/i2c/busses/i2c-qcom-geni.c | 43 
>> ++++++++++++++++++++++++++++++
>>  include/linux/qcom-geni-se.h       |  5 ++++
>>  2 files changed, 48 insertions(+)
>> 
>> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c 
>> b/drivers/i2c/busses/i2c-qcom-geni.c
>> index 1fda5c7c2cfc..d07f2f33bb75 100644
>> --- a/drivers/i2c/busses/i2c-qcom-geni.c
>> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
>> @@ -486,6 +486,28 @@ static int geni_i2c_xfer(struct i2c_adapter 
>> *adap,
>>         return ret;
>>  }
>> 
>> +static void geni_i2c_stop_xfer(struct geni_i2c_dev *gi2c)
>> +{
>> +       u32 val;
>> +       struct geni_se *se = &gi2c->se;
>> +
>> +       val = readl_relaxed(gi2c->se.base + SE_DMA_DEBUG_REG0);
>> +       if (val & DMA_TX_ACTIVE) {
>> +               geni_i2c_abort_xfer(gi2c);
>> +               gi2c->cur_wr = 0;
>> +               if (gi2c->err)
>> +                       geni_i2c_tx_fsm_rst(gi2c);
>> +               geni_se_tx_dma_unprep(se, gi2c->tx_dma, 
>> gi2c->xfer_len);
>> +       }
>> +       if (val & DMA_RX_ACTIVE) {
>> +               geni_i2c_abort_xfer(gi2c);
>> +               gi2c->cur_rd = 0;
>> +               if (gi2c->err)
>> +                       geni_i2c_rx_fsm_rst(gi2c);
>> +               geni_se_rx_dma_unprep(se, gi2c->rx_dma, 
>> gi2c->xfer_len);
>> +       }
>> +}
>> +
>>  static u32 geni_i2c_func(struct i2c_adapter *adap)
>>  {
>>         return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & 
>> ~I2C_FUNC_SMBUS_QUICK);
>> @@ -617,6 +639,26 @@ static int geni_i2c_remove(struct platform_device 
>> *pdev)
>>         return 0;
>>  }
>> 
>> +static void geni_i2c_shutdown(struct platform_device *pdev)
>> +{
>> +       int ret;
>> +       u32 dma;
>> +       struct geni_i2c_dev *gi2c = platform_get_drvdata(pdev);
>> +       struct geni_se *se = &gi2c->se;
>> +
>> +       ret = pm_runtime_get_sync(gi2c->se.dev);
>> +       if (ret < 0) {
>> +               dev_err(gi2c->se.dev, "Failed to resume device: %d\n", 
>> ret);
>> +               return;
>> +       }
>> +
>> +       dma = readl_relaxed(se->base + SE_GENI_DMA_MODE_EN);
>> +       if (dma)
>> +               geni_i2c_stop_xfer(gi2c);
> 
> Any reason the if (dma) check isn't inside geni_i2c_stop_xfer()?
> Checking for dma and then bailing out early should work and keep the
> logic in one function. Then the pm_runtime_sync() call could go in 
> there
> too and if (!dma) goto out. This assumes that we're going to call
> geni_i2c_stop_xfer() from somewhere else, like if a transfer times out
> or something?
> 

Okay, will do the changes.

>> +
>> +       pm_runtime_put_sync_suspend(gi2c->se.dev);
>> +}
>> +
>>  static int __maybe_unused geni_i2c_runtime_suspend(struct device 
>> *dev)
>>  {
>>         int ret;