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Date:   Thu, 17 Sep 2020 17:33:30 +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,
        msavaliy@qti.qualcomm.com, skakit@codeaurora.org,
        rnayak@codeaurora.org, agross@kernel.org,
        bjorn.andersson@linaro.org, linux-arm-msm@vger.kernel.org,
        linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
        sumit.semwal@linaro.org, linux-media@vger.kernel.org
Subject: Re: [PATCH V3] i2c: i2c-qcom-geni: Add shutdown callback for i2c
In-Reply-To: <159959341894.454335.3250696075143737399@swboyd.mtv.corp.google.com>
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 <159959341894.454335.3250696075143737399@swboyd.mtv.corp.google.com>
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Hi Stephen,

On 2020-09-09 01:00, Stephen Boyd wrote:
> Why is dri-devel on here? And linaro-mm-sig?
> 

Ok, I will remove these lists.

> Quoting Roja Rani Yarubandi (2020-09-07 06:07:31)
>> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c 
>> b/drivers/i2c/busses/i2c-qcom-geni.c
>> index dead5db3315a..b3609760909f 100644
>> --- a/drivers/i2c/busses/i2c-qcom-geni.c
>> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
>>  struct geni_i2c_err_log {
>> @@ -384,7 +387,8 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev 
>> *gi2c, struct i2c_msg *msg,
>>         if (dma_buf) {
>>                 if (gi2c->err)
>>                         geni_i2c_rx_fsm_rst(gi2c);
>> -               geni_se_rx_dma_unprep(se, rx_dma, len);
>> +               geni_se_rx_dma_unprep(se, gi2c->rx_dma, len);
>> +               gi2c->rx_dma = (dma_addr_t)NULL;
>>                 i2c_put_dma_safe_msg_buf(dma_buf, msg, !gi2c->err);
>>         }
>> 
>> @@ -394,12 +398,12 @@ static int geni_i2c_rx_one_msg(struct 
>> geni_i2c_dev *gi2c, struct i2c_msg *msg,
>>  static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct 
>> i2c_msg *msg,
>>                                 u32 m_param)
>>  {
>> -       dma_addr_t tx_dma;
>>         unsigned long time_left;
>>         void *dma_buf = NULL;
>>         struct geni_se *se = &gi2c->se;
>>         size_t len = msg->len;
>> 
>> +       gi2c->xfer_len = len;
>>         if (!of_machine_is_compatible("lenovo,yoga-c630"))
>>                 dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
>> 
>> @@ -410,7 +414,7 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev 
>> *gi2c, struct i2c_msg *msg,
>> 
>>         writel_relaxed(len, se->base + SE_I2C_TX_TRANS_LEN);
>> 
>> -       if (dma_buf && geni_se_tx_dma_prep(se, dma_buf, len, &tx_dma)) 
>> {
>> +       if (dma_buf && geni_se_tx_dma_prep(se, dma_buf, len, 
>> &gi2c->tx_dma)) {
>>                 geni_se_select_mode(se, GENI_SE_FIFO);
>>                 i2c_put_dma_safe_msg_buf(dma_buf, msg, false);
>>                 dma_buf = NULL;
>> @@ -429,7 +433,8 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev 
>> *gi2c, struct i2c_msg *msg,
>>         if (dma_buf) {
>>                 if (gi2c->err)
>>                         geni_i2c_tx_fsm_rst(gi2c);
>> -               geni_se_tx_dma_unprep(se, tx_dma, len);
>> +               geni_se_tx_dma_unprep(se, gi2c->tx_dma, len);
>> +               gi2c->tx_dma = (dma_addr_t)NULL;
>>                 i2c_put_dma_safe_msg_buf(dma_buf, msg, !gi2c->err);
>>         }
>> 
>> @@ -479,6 +484,51 @@ static int geni_i2c_xfer(struct i2c_adapter 
>> *adap,
>>         return ret;
>>  }
>> 
>> +static void geni_i2c_stop_xfer(struct geni_i2c_dev *gi2c)
>> +{
>> +       int ret;
>> +       u32 dma;
>> +       u32 val;
>> +       u32 geni_status;
>> +       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);
> 
> Is this print really necessary? Doesn't PM core already print this sort
> of information?
> 

PM core will not print any such information.
Here we wanted to know our driver's pm runtime resume is successful.

>> +               return;
>> +       }
>> +
>> +       geni_status = readl_relaxed(gi2c->se.base + SE_GENI_STATUS);
>> +       if (geni_status & M_GENI_CMD_ACTIVE) {
> 
> Please try to de-indent all this.
> 

Okay.

> 	if (!(geni_status & M_GENI_CMD_ACTIVE))
> 		goto out;
> 
>> +               geni_i2c_abort_xfer(gi2c);
>> +               dma = readl_relaxed(se->base + SE_GENI_DMA_MODE_EN);
>> +               if (dma) {
> 
> 	if (!dma)
> 		goto out;
> 
>> +                       val = readl_relaxed(gi2c->se.base + 
>> SE_DMA_DEBUG_REG0);
>> +                       if (val & DMA_TX_ACTIVE) {
>> +                               gi2c->cur_wr = 0;
>> +                               if (gi2c->err)
>> +                                       geni_i2c_tx_fsm_rst(gi2c);
>> +                               if (gi2c->tx_dma) {
>> +                                       geni_se_tx_dma_unprep(se,
>> +                                                gi2c->tx_dma, 
>> gi2c->xfer_len);
>> +                                       gi2c->tx_dma = 
>> (dma_addr_t)NULL;
> 
> Almost nobody does this. In fact, grep shows me one hit in the kernel.
> If nobody else is doing it something is probably wrong. When would dma
> mode be active and tx_dma not be set to something that should be
> stopped? If it really is necessary I suppose we should assign this to
> DMA_MAPPING_ERROR instead of casting NULL. Then the check above for
> tx_dma being valid can be dropped because geni_se_tx_dma_unprep()
> already checks for a valid mapping before doing anything. But really, 
> we
> should probably be tracking the dma buffer mapped to the CPU as well as
> the dma address that was used for the mapping. Not storing both is a
> problem, see below.
> 

You are correct, setting gi2c->tx_dma to NULL and check for tx_dma is
not required. Will correct this.

>> +                               }
>> +                       } else if (val & DMA_RX_ACTIVE) {
>> +                               gi2c->cur_rd = 0;
>> +                               if (gi2c->err)
>> +                                       geni_i2c_rx_fsm_rst(gi2c);
>> +                               if (gi2c->rx_dma) {
>> +                                       geni_se_rx_dma_unprep(se,
>> +                                               gi2c->rx_dma, 
>> gi2c->xfer_len);
> 
> Looking closely it seems that the geni dma wrappers shouldn't even be
> checking for an iova being non-zero. Instead they should make sure that
> it just isn't invalid with !dma_mapping_error().
> 

Yes. I will remove iova check in geni_se_rx_dma_unprep() function(also 
in tx_dma_unprep)

>> +                                       gi2c->rx_dma = 
>> (dma_addr_t)NULL;
> 
> If we're stopping some dma transaction doesn't that mean the
> 
>                  i2c_put_dma_safe_msg_buf(dma_buf, msg, !gi2c->err);
> 
> code needs to run also? I fail to see where we free the buffer that has
> been mapped for DMA.
> 

Yes, this is required. I will do this cleanup.

>> +                               }
>> +                       }
>> +               }
>> +       }
>> +
> 
> out:
> 
>> +       pm_runtime_put_sync_suspend(gi2c->se.dev);
>> +}
>> +