linux-kernel - Re: [PATCH] staging: iio: ad2s1210: Fix SPI reading

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Date:   Mon, 4 May 2020 06:29:08 +0000
From:   "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>
To:     "jic23@...nel.org" <jic23@...nel.org>
CC:     "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "Bogdan, Dragos" <Dragos.Bogdan@...log.com>
Subject: Re: [PATCH] staging: iio: ad2s1210: Fix SPI reading

On Sun, 2020-05-03 at 12:37 +0100, Jonathan Cameron wrote:
> [External]
> 
> On Wed, 29 Apr 2020 10:21:29 +0300
> Alexandru Ardelean <alexandru.ardelean@...log.com> wrote:
> 
> > From: Dragos Bogdan <dragos.bogdan@...log.com>
> > 
> > If the serial interface is used, the 8-bit address should be latched using
> > the rising edge of the WR/FSYNC signal.
> > 
> > This basically means that a CS change is required between the first byte
> > sent, and the second one.
> > This change splits the single-transfer transfer of 2 bytes into 2 transfers
> > with a single byte, and CS change in-between.
> > 
> > Signed-off-by: Dragos Bogdan <dragos.bogdan@...log.com>
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
> 
> Fixes tag would have been nice. I've had a go by picking a patch where I
> refactored this code, but I think the issue probably predates that one.
> Its in 2011 so I doubt anyone will try going past that with backports ;)
> 

Apologies again for not considering Fixes tag.
At this point, I feel bad for repeating the apology, as it may sound like hollow

words.
But, I guess this could have skipped going through the fixes route.
The patch has been living in our tree for a while.

> Applied to the fixes-togreg branch of iio.git and marked for stable.
> 
> I'm guessing this means you have hardware and hope to get this one out
> of staging shortly? *crosses fingers* :)

Sorry, but not at this point in time.
I just fished this from our tree.
I also handle our kernel upgrades [on our side], and whenever I do an update,
some upstreamed patches disappear from our tree, and some stand-out and I wonder
how come this wasn't sent upstream.
This is one of them.

I don't know if I'll be able to find someone [in the near future] to allocate
this to [for moving out-of-staging].
Right now, the priority [on our side] is the high-speed converters.


> 
> Jonathan
> 
> > ---
> >  drivers/staging/iio/resolver/ad2s1210.c | 17 ++++++++++++-----
> >  1 file changed, 12 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/staging/iio/resolver/ad2s1210.c
> > b/drivers/staging/iio/resolver/ad2s1210.c
> > index 4b25a3a314ed..ed404355ea4c 100644
> > --- a/drivers/staging/iio/resolver/ad2s1210.c
> > +++ b/drivers/staging/iio/resolver/ad2s1210.c
> > @@ -130,17 +130,24 @@ static int ad2s1210_config_write(struct ad2s1210_state
> > *st, u8 data)
> >  static int ad2s1210_config_read(struct ad2s1210_state *st,
> >  				unsigned char address)
> >  {
> > -	struct spi_transfer xfer = {
> > -		.len = 2,
> > -		.rx_buf = st->rx,
> > -		.tx_buf = st->tx,
> > +	struct spi_transfer xfers[] = {
> > +		{
> > +			.len = 1,
> > +			.rx_buf = &st->rx[0],
> > +			.tx_buf = &st->tx[0],
> > +			.cs_change = 1,
> > +		}, {
> > +			.len = 1,
> > +			.rx_buf = &st->rx[1],
> > +			.tx_buf = &st->tx[1],
> > +		},
> >  	};
> >  	int ret = 0;
> >  
> >  	ad2s1210_set_mode(MOD_CONFIG, st);
> >  	st->tx[0] = address | AD2S1210_MSB_IS_HIGH;
> >  	st->tx[1] = AD2S1210_REG_FAULT;
> > -	ret = spi_sync_transfer(st->sdev, &xfer, 1);
> > +	ret = spi_sync_transfer(st->sdev, xfers, 2);
> >  	if (ret < 0)
> >  		return ret;
> >