On Wednesday 05 October 2016 02:16 PM, Peter Ujfalusi wrote:
> On 10/05/16 11:17, Mugunthan V N wrote:
>> On Wednesday 05 October 2016 12:01 PM, Peter Ujfalusi wrote:
>>> On 10/05/16 09:21, Mugunthan V N wrote:
>>>> On Tuesday 04 October 2016 02:02 PM, Peter Ujfalusi wrote:
>>>>> On 10/03/16 16:03, Mugunthan V N wrote:
>>>>>> +static int tiadc_request_dma(struct platform_device *pdev,
>>>>>> + struct tiadc_device *adc_dev)
>>>>>> +{
>>>>>> + struct tiadc_dma *dma = &adc_dev->dma;
>>>>>> + dma_cap_mask_t mask;
>>>>>> +
>>>>>> + /* Default slave configuration parameters */
>>>>>> + dma->conf.direction = DMA_DEV_TO_MEM;
>>>>>> + dma->conf.src_addr_width = DMA_SLAVE_BUSWIDTH_2_BYTES;
>>>>>> + dma->conf.src_addr = adc_dev->mfd_tscadc->tscadc_phys_base + REG_FIFO1;
>>>>>> +
>>>>>> + dma_cap_zero(mask);
>>>>>> + dma_cap_set(DMA_CYCLIC, mask);
>>>>>> +
>>>>>> + /* Get a channel for RX */
>>>>>> + dma->chan = dma_request_chan(adc_dev->mfd_tscadc->dev, "fifo1");
>>>>>> + if (!dma->chan)
>>>>>> + return -ENODEV;
>>>>>
>>>>> dma_request_chan() ERR_PTR in case of failure, never NULL. You should reuse
>>>>> the returned error code to support deferred probing.
>>>>
>>>> Will fix this in v3.
>>>>
>>>>>
>>>>>> +
>>>>>> + /* RX buffer */
>>>>>> + dma->buf = dma_alloc_coherent(dma->chan->device->dev, DMA_BUFFER_SIZE,
>>>>>> + &dma->addr, GFP_KERNEL);
>>>>>> + if (!dma->buf)
>>>>>> + goto err;
>>>>>> +
>>>>>> + return 0;
>>>>>> +err:
>>>>>> + dma_release_channel(dma->chan);
>>>>>> +
>>>>>> + return -ENOMEM;
>>>>>> +}
>>>>>> +
>>>>>> static int tiadc_parse_dt(struct platform_device *pdev,
>>>>>> struct tiadc_device *adc_dev)
>>>>>> {
>>>>>> @@ -512,8 +639,14 @@ static int tiadc_probe(struct platform_device *pdev)
>>>>>>
>>>>>> platform_set_drvdata(pdev, indio_dev);
>>>>>>
>>>>>> + err = tiadc_request_dma(pdev, adc_dev);
>>>>>> + if (err && err != -ENODEV)
>>>>>> + goto err_dma;
>>>>>
>>>>> You should handle the deferred probing for DMA channel.
>>>>
>>>> + dma->chan = dma_request_chan(adc_dev->mfd_tscadc->dev, "fifo1");
>>>> + if (IS_ERR(dma->chan)) {
>>>> + int ret = PTR_ERR(dma->chan);
>>>> +
>>>> + dma->chan = NULL;
>>>> + return ret;
>>>
>>> You don't need the 'ret' variable:
>>> return PTR_ERR(dma->chan);
>>
>> So you mean change all *if (dma->chan)* to *if (IS_ERR(dma->chan))*?
>
> Oh, sorry. Your version was fine as you NULL the dma->chan before the return.
>
>>
>>>
>>>> + }
>>>>
>>>> With this probe defer will be taken care and ADC will continue without
>>>> DMA when request channel returns -ENODEV.
>>>
>>> I would rather have explicit check for deferred probe:
>>>
>>> err = tiadc_request_dma(pdev, adc_dev);
>>> if (err && err == -EPROBE_DEFER)
>>> goto err_dma;
>>
>> But in this case any other failure other than -EPROBE_DEFER will be
>> masked and ADC will be in PIO mode?
>
> Yes, exactly. If we fail to get the DMA channel we should not use the DMA and
> we only want to handle the deferred probing.
>
Okay, will update accordingly in next version.
Regards
Mugunthan V N
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