linux-kernel - Re: [PATCH V5 3/3] i2c: i2c-qcom-geni: Add shutdown callback for i2c

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Date:   Fri, 30 Oct 2020 20:29:31 +0530
From:   rojay@...eaurora.org
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     wsa@...nel.org, dianders@...omium.org,
        saiprakash.ranjan@...eaurora.org, gregkh@...uxfoundation.org,
        mka@...omium.org, akashast@...eaurora.org,
        msavaliy@....qualcomm.com, skakit@...eaurora.org,
        vkaur@...eaurora.org, pyarlaga@...eaurora.org,
        rnayak@...eaurora.org, agross@...nel.org,
        bjorn.andersson@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        sumit.semwal@...aro.org, linux-media@...r.kernel.org
Subject: Re: [PATCH V5 3/3] i2c: i2c-qcom-geni: Add shutdown callback for i2c

Hi Stephen,

On 2020-10-03 07:09, Stephen Boyd wrote:
> Quoting Roja Rani Yarubandi (2020-10-01 01:44:25)
>> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c 
>> b/drivers/i2c/busses/i2c-qcom-geni.c
>> index aee2a1dd2c62..56d3fbfe7eb6 100644
>> --- a/drivers/i2c/busses/i2c-qcom-geni.c
>> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
>> @@ -380,6 +380,36 @@ static void geni_i2c_tx_msg_cleanup(struct 
>> geni_i2c_dev *gi2c,
>>         }
>>  }
>> 
>> +static void geni_i2c_stop_xfer(struct geni_i2c_dev *gi2c)
>> +{
>> +       int ret;
>> +       u32 geni_status;
>> +       unsigned long flags;
>> +       struct i2c_msg *cur;
>> +
>> +       /* Resume device, runtime suspend can happen anytime during 
>> transfer */
>> +       ret = pm_runtime_get_sync(gi2c->se.dev);
>> +       if (ret < 0) {
>> +               dev_err(gi2c->se.dev, "Failed to resume device: %d\n", 
>> ret);
>> +               return;
>> +       }
>> +
>> +       spin_lock_irqsave(&gi2c->lock, flags);
> 
> We grab the lock here.
> 
>> +       geni_status = readl_relaxed(gi2c->se.base + SE_GENI_STATUS);
>> +       if (!(geni_status & M_GENI_CMD_ACTIVE))
>> +               goto out;
>> +
>> +       cur = gi2c->cur;
>> +       geni_i2c_abort_xfer(gi2c);
> 
> But it looks like this function takes the lock again? Did you test this
> with lockdep enabled? It should hang even without lockdep, so it seems
> like this path of code has not been tested.
> 

Tested with lockdep enabled, and fixed the unsafe lock order issue here.
And to be more proper moved spin_lock/unlock to cleanup functions.

>> +       if (cur->flags & I2C_M_RD)
>> +               geni_i2c_rx_msg_cleanup(gi2c, cur);
>> +       else
>> +               geni_i2c_tx_msg_cleanup(gi2c, cur);
>> +       spin_unlock_irqrestore(&gi2c->lock, flags);
>> +out:
>> +       pm_runtime_put_sync_suspend(gi2c->se.dev);
>> +}
>> +
>>  static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct 
>> i2c_msg *msg,
>>                                 u32 m_param)
>>  {