On 10/28/21 5:34 PM, Jonathan Cameron wrote:
> On Tue, 19 Oct 2021 10:29:28 +0200
> Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
>
>> The at91-sama5d2 driver calls `to_platform_device()` on a struct device
>> that is part of a IIO device. This is incorrect since
>> `to_platform_device()` must only be called on a struct device that is part
>> of a platform device.
>>
>> The code still works by accident because non of the struct platform_device
>> specific fields are accessed.
>>
>> Refactor the code a bit so that it behaves identically, but does not use
>> the incorrect cast. This avoids accidentally adding undefined behavior in
>> the future by assuming the `struct platform_device` is actually valid.
>>
>> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
>
> This makes me nervous for the reason you give below.
> Looking for a response from Eugen or someone else with access to the device
> before I apply this one.
Hi,
I will take some time to test this on my setup. Thanks for the patch,
and sorry for the delays !
Eugen
>
> Thanks,
>
> Jonathan
>
>> ---
>> The code is equivalent to before, but I'm a bit confused how this works.
>> We call dma_request_chan() on the IIO device's struct device. Which should
>> not yield any results.
>>
>> Eugen can you check if/why this works and see if a follow up patch using
>> the right struct device (the platform_device's) to request the DMA channel
>> makes sense?
>> ---
>> drivers/iio/adc/at91-sama5d2_adc.c | 34 ++++++++++++++----------------
>> 1 file changed, 16 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
>> index 4c922ef634f8..3841e7b6c81d 100644
>> --- a/drivers/iio/adc/at91-sama5d2_adc.c
>> +++ b/drivers/iio/adc/at91-sama5d2_adc.c
>> @@ -1661,10 +1661,9 @@ static int at91_adc_write_raw(struct iio_dev *indio_dev,
>> }
>> }
>>
>> -static void at91_adc_dma_init(struct platform_device *pdev)
>> +static void at91_adc_dma_init(struct at91_adc_state *st)
>> {
>> - struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>> - struct at91_adc_state *st = iio_priv(indio_dev);
>> + struct device *dev = &st->indio_dev->dev;
>> struct dma_slave_config config = {0};
>> /* we have 2 bytes for each channel */
>> unsigned int sample_size = st->soc_info.platform->nr_channels * 2;
>> @@ -1679,9 +1678,9 @@ static void at91_adc_dma_init(struct platform_device *pdev)
>> if (st->dma_st.dma_chan)
>> return;
>>
>> - st->dma_st.dma_chan = dma_request_chan(&pdev->dev, "rx");
>> + st->dma_st.dma_chan = dma_request_chan(dev, "rx");
>> if (IS_ERR(st->dma_st.dma_chan)) {
>> - dev_info(&pdev->dev, "can't get DMA channel\n");
>> + dev_info(dev, "can't get DMA channel\n");
>> st->dma_st.dma_chan = NULL;
>> goto dma_exit;
>> }
>> @@ -1691,7 +1690,7 @@ static void at91_adc_dma_init(struct platform_device *pdev)
>> &st->dma_st.rx_dma_buf,
>> GFP_KERNEL);
>> if (!st->dma_st.rx_buf) {
>> - dev_info(&pdev->dev, "can't allocate coherent DMA area\n");
>> + dev_info(dev, "can't allocate coherent DMA area\n");
>> goto dma_chan_disable;
>> }
>>
>> @@ -1704,11 +1703,11 @@ static void at91_adc_dma_init(struct platform_device *pdev)
>> config.dst_maxburst = 1;
>>
>> if (dmaengine_slave_config(st->dma_st.dma_chan, &config)) {
>> - dev_info(&pdev->dev, "can't configure DMA slave\n");
>> + dev_info(dev, "can't configure DMA slave\n");
>> goto dma_free_area;
>> }
>>
>> - dev_info(&pdev->dev, "using %s for rx DMA transfers\n",
>> + dev_info(dev, "using %s for rx DMA transfers\n",
>> dma_chan_name(st->dma_st.dma_chan));
>>
>> return;
>> @@ -1720,13 +1719,12 @@ static void at91_adc_dma_init(struct platform_device *pdev)
>> dma_release_channel(st->dma_st.dma_chan);
>> st->dma_st.dma_chan = NULL;
>> dma_exit:
>> - dev_info(&pdev->dev, "continuing without DMA support\n");
>> + dev_info(dev, "continuing without DMA support\n");
>> }
>>
>> -static void at91_adc_dma_disable(struct platform_device *pdev)
>> +static void at91_adc_dma_disable(struct at91_adc_state *st)
>> {
>> - struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>> - struct at91_adc_state *st = iio_priv(indio_dev);
>> + struct device *dev = &st->indio_dev->dev;
>> /* we have 2 bytes for each channel */
>> unsigned int sample_size = st->soc_info.platform->nr_channels * 2;
>> unsigned int pages = DIV_ROUND_UP(AT91_HWFIFO_MAX_SIZE *
>> @@ -1744,7 +1742,7 @@ static void at91_adc_dma_disable(struct platform_device *pdev)
>> dma_release_channel(st->dma_st.dma_chan);
>> st->dma_st.dma_chan = NULL;
>>
>> - dev_info(&pdev->dev, "continuing without DMA support\n");
>> + dev_info(dev, "continuing without DMA support\n");
>> }
>>
>> static int at91_adc_set_watermark(struct iio_dev *indio_dev, unsigned int val)
>> @@ -1770,9 +1768,9 @@ static int at91_adc_set_watermark(struct iio_dev *indio_dev, unsigned int val)
>> */
>>
>> if (val == 1)
>> - at91_adc_dma_disable(to_platform_device(&indio_dev->dev));
>> + at91_adc_dma_disable(st);
>> else if (val > 1)
>> - at91_adc_dma_init(to_platform_device(&indio_dev->dev));
>> + at91_adc_dma_init(st);
>>
>> /*
>> * We can start the DMA only after setting the watermark and
>> @@ -1780,7 +1778,7 @@ static int at91_adc_set_watermark(struct iio_dev *indio_dev, unsigned int val)
>> */
>> ret = at91_adc_buffer_prepare(indio_dev);
>> if (ret)
>> - at91_adc_dma_disable(to_platform_device(&indio_dev->dev));
>> + at91_adc_dma_disable(st);
>>
>> return ret;
>> }
>> @@ -2077,7 +2075,7 @@ static int at91_adc_probe(struct platform_device *pdev)
>> return 0;
>>
>> dma_disable:
>> - at91_adc_dma_disable(pdev);
>> + at91_adc_dma_disable(st);
>> per_clk_disable_unprepare:
>> clk_disable_unprepare(st->per_clk);
>> vref_disable:
>> @@ -2094,7 +2092,7 @@ static int at91_adc_remove(struct platform_device *pdev)
>>
>> iio_device_unregister(indio_dev);
>>
>> - at91_adc_dma_disable(pdev);
>> + at91_adc_dma_disable(st);
>>
>> clk_disable_unprepare(st->per_clk);
>>
>
