Re: [PATCH] iio: at91-sama5d2_adc: remove usage of iio_priv_to_dev() helper

["Ardelean, Alexandru" <alexandru.Ardelean@analog.com>]

On Wed, 2020-06-17 at 13:25 +0000, Eugen.Hristev@microchip.com wrote:
> On 31.05.2020 17:39, Jonathan Cameron wrote:
> 
> > On Mon, 25 May 2020 13:53:41 +0300
> > Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:
> > 
> > > We may want to get rid of the iio_priv_to_dev() helper. The reason is that
> > > we will hide some of the members of the iio_dev structure (to prevent
> > > drivers from accessing them directly), and that will also mean hiding the
> > > implementation of the iio_priv_to_dev() helper inside the IIO core.
> > > 
> > > Hiding the implementation of iio_priv_to_dev() implies that some fast-
> > > paths
> > > may not be fast anymore, so a general idea is to try to get rid of the
> > > iio_priv_to_dev() altogether.
> > > The iio_priv() helper won't be affected by the rework, as the iio_dev
> > > struct will keep a reference to the private information.
> > > 
> > > For this driver, not using iio_priv_to_dev(), means reworking some paths
> > > to
> > > pass the iio device and using iio_priv() to access the private
> > > information,
> > > and also keeping a reference to the iio device for some quirky paths.
> > > 
> > > One [quirky] path is the at91_adc_workq_handler() which requires the IIO
> > > device & the state struct to push to buffers.
> > > Since this requires the back-ref to the IIO device, the
> > > at91_adc_touch_pos() also uses it. This simplifies the patch a bit. The
> > > information required in this function is mostly for debugging purposes.
> > > Replacing it with a reference to the IIO device would have been a slightly
> > > bigger change, which may not be worth it (for just the debugging purpose
> > > and given that we need the back-ref to the IIO device anyway).
> > 
> > That workq is indeed quirky.  This looks fine to me in general. I'll
> > want an appropriate ack from the at91 side of things if possible so
> > let's leave this on the list for a while longer.
> 
> Hi,
> 
> I am available to test this patch,
> Can you tell me on which branch to apply it. On 5.8-rc1 it fails for me
> (or maybe it needs rebasing ?)
> 

Hmm, weird.
I rebased the patches on Jonathan's iio/testing.
It seemed to work.
https://github.com/commodo/linux/commits/iio-priv-to-dev

As for which branch to test/apply. Not sure.
Maybe Jonathan's iio/testing as base?
Looks like it's based on 5.8.


> Eugen
> 
> > Poke me if no action in a few weeks.
> > 
> > Thanks,
> > 
> > Jonathan
> > 
> > > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > > ---
> > >   drivers/iio/adc/at91-sama5d2_adc.c | 30 +++++++++++++++++-------------
> > >   1 file changed, 17 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-
> > > sama5d2_adc.c
> > > index 9abbbdcc7420..7bce18444430 100644
> > > --- a/drivers/iio/adc/at91-sama5d2_adc.c
> > > +++ b/drivers/iio/adc/at91-sama5d2_adc.c
> > > @@ -402,6 +402,7 @@ struct at91_adc_state {
> > >        wait_queue_head_t               wq_data_available;
> > >        struct at91_adc_dma             dma_st;
> > >        struct at91_adc_touch           touch_st;
> > > +     struct iio_dev                  *indio_dev;
> > >        u16                             buffer[AT91_BUFFER_MAX_HWORDS];
> > >        /*
> > >         * lock to prevent concurrent 'single conversion' requests through
> > > @@ -642,13 +643,13 @@ static u16 at91_adc_touch_pos(struct at91_adc_state
> > > *st, int reg)
> > >        /* first half of register is the x or y, second half is the scale
> > > */
> > >        val = at91_adc_readl(st, reg);
> > >        if (!val)
> > > -             dev_dbg(&iio_priv_to_dev(st)->dev, "pos is 0\n");
> > > +             dev_dbg(&st->indio_dev->dev, "pos is 0\n");
> > > 
> > >        pos = val & AT91_SAMA5D2_XYZ_MASK;
> > >        result = (pos << AT91_SAMA5D2_MAX_POS_BITS) - pos;
> > >        scale = (val >> 16) & AT91_SAMA5D2_XYZ_MASK;
> > >        if (scale == 0) {
> > > -             dev_err(&iio_priv_to_dev(st)->dev, "scale is 0\n");
> > > +             dev_err(&st->indio_dev->dev, "scale is 0\n");
> > >                return 0;
> > >        }
> > >        result /= scale;
> > > @@ -1204,9 +1205,9 @@ static unsigned at91_adc_startup_time(unsigned
> > > startup_time_min,
> > >        return i;
> > >   }
> > > 
> > > -static void at91_adc_setup_samp_freq(struct at91_adc_state *st, unsigned
> > > freq)
> > > +static void at91_adc_setup_samp_freq(struct iio_dev *indio_dev, unsigned
> > > freq)
> > >   {
> > > -     struct iio_dev *indio_dev = iio_priv_to_dev(st);
> > > +     struct at91_adc_state *st = iio_priv(indio_dev);
> > >        unsigned f_per, prescal, startup, mr;
> > > 
> > >        f_per = clk_get_rate(st->per_clk);
> > > @@ -1275,9 +1276,9 @@ static void at91_adc_pen_detect_interrupt(struct
> > > at91_adc_state *st)
> > >        st->touch_st.touching = true;
> > >   }
> > > 
> > > -static void at91_adc_no_pen_detect_interrupt(struct at91_adc_state *st)
> > > +static void at91_adc_no_pen_detect_interrupt(struct iio_dev *indio_dev)
> > >   {
> > > -     struct iio_dev *indio_dev = iio_priv_to_dev(st);
> > > +     struct at91_adc_state *st = iio_priv(indio_dev);
> > > 
> > >        at91_adc_writel(st, AT91_SAMA5D2_TRGR,
> > >                        AT91_SAMA5D2_TRGR_TRGMOD_NO_TRIGGER);
> > > @@ -1297,7 +1298,7 @@ static void at91_adc_workq_handler(struct
> > > work_struct *workq)
> > >                                        struct at91_adc_touch, workq);
> > >        struct at91_adc_state *st = container_of(touch_st,
> > >                                        struct at91_adc_state, touch_st);
> > > -     struct iio_dev *indio_dev = iio_priv_to_dev(st);
> > > +     struct iio_dev *indio_dev = st->indio_dev;
> > > 
> > >        iio_push_to_buffers(indio_dev, st->buffer);
> > >   }
> > > @@ -1318,7 +1319,7 @@ static irqreturn_t at91_adc_interrupt(int irq, void
> > > *private)
> > >                at91_adc_pen_detect_interrupt(st);
> > >        } else if ((status & AT91_SAMA5D2_IER_NOPEN)) {
> > >                /* nopen detected IRQ */
> > > -             at91_adc_no_pen_detect_interrupt(st);
> > > +             at91_adc_no_pen_detect_interrupt(indio);
> > >        } else if ((status & AT91_SAMA5D2_ISR_PENS) &&
> > >                   ((status & rdy_mask) == rdy_mask)) {
> > >                /* periodic trigger IRQ - during pen sense */
> > > @@ -1486,7 +1487,7 @@ static int at91_adc_write_raw(struct iio_dev
> > > *indio_dev,
> > >                    val > st->soc_info.max_sample_rate)
> > >                        return -EINVAL;
> > > 
> > > -             at91_adc_setup_samp_freq(st, val);
> > > +             at91_adc_setup_samp_freq(indio_dev, val);
> > >                return 0;
> > >        default:
> > >                return -EINVAL;
> > > @@ -1624,8 +1625,10 @@ static int at91_adc_update_scan_mode(struct iio_dev
> > > *indio_dev,
> > >        return 0;
> > >   }
> > > 
> > > -static void at91_adc_hw_init(struct at91_adc_state *st)
> > > +static void at91_adc_hw_init(struct iio_dev *indio_dev)
> > >   {
> > > +     struct at91_adc_state *st = iio_priv(indio_dev);
> > > +
> > >        at91_adc_writel(st, AT91_SAMA5D2_CR, AT91_SAMA5D2_CR_SWRST);
> > >        at91_adc_writel(st, AT91_SAMA5D2_IDR, 0xffffffff);
> > >        /*
> > > @@ -1635,7 +1638,7 @@ static void at91_adc_hw_init(struct at91_adc_state
> > > *st)
> > >        at91_adc_writel(st, AT91_SAMA5D2_MR,
> > >                        AT91_SAMA5D2_MR_TRANSFER(2) |
> > > AT91_SAMA5D2_MR_ANACH);
> > > 
> > > -     at91_adc_setup_samp_freq(st, st->soc_info.min_sample_rate);
> > > +     at91_adc_setup_samp_freq(indio_dev, st->soc_info.min_sample_rate);
> > > 
> > >        /* configure extended mode register */
> > >        at91_adc_config_emr(st);
> > > @@ -1718,6 +1721,7 @@ static int at91_adc_probe(struct platform_device
> > > *pdev)
> > >        indio_dev->num_channels = ARRAY_SIZE(at91_adc_channels);
> > > 
> > >        st = iio_priv(indio_dev);
> > > +     st->indio_dev = indio_dev;
> > > 
> > >        bitmap_set(&st->touch_st.channels_bitmask,
> > >                   AT91_SAMA5D2_TOUCH_X_CHAN_IDX, 1);
> > > @@ -1829,7 +1833,7 @@ static int at91_adc_probe(struct platform_device
> > > *pdev)
> > >                goto vref_disable;
> > >        }
> > > 
> > > -     at91_adc_hw_init(st);
> > > +     at91_adc_hw_init(indio_dev);
> > > 
> > >        ret = clk_prepare_enable(st->per_clk);
> > >        if (ret)
> > > @@ -1945,7 +1949,7 @@ static __maybe_unused int at91_adc_resume(struct
> > > device *dev)
> > >        if (ret)
> > >                goto vref_disable_resume;
> > > 
> > > -     at91_adc_hw_init(st);
> > > +     at91_adc_hw_init(indio_dev);
> > > 
> > >        /* reconfiguring trigger hardware state */
> > >        if (!iio_buffer_enabled(indio_dev))