Re: [PATCH] iio: proximity: sx9324: Correct proximity channel resolution

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 18 Aug 2026 11:26:39 +0300
Andy Shevchenko <andriy.shevchenko@intel.com> wrote:

> On Tue, Aug 18, 2026 at 03:28:03PM +0800, Zhang Jie wrote:
> > The proximity channels were previously defined with 12 realbits.
> > However, PROXDIFF is read from RegDiffMsb (0x65) and RegDiffLsb
> > (0x66). The SX9324 datasheet assigns bits 7:0 of each register to
> > PROXDIFF and documents it as a signed two's-complement value
> > (Revision 3, Section 8, Table 8, page 43). In contrast, RegOffsetMsb
> > explicitly marks bits 7:6 as reserved. Thus, PROXDIFF is a 16-bit
> > signed value.
> > 
> > With realbits = 12, sx_common_read_proximity() uses bit 11 as the
> > sign bit in sign_extend32(), causing samples outside the 12-bit
> > signed range to wrap into the [-2048, 2047] range.
> > 
> > Correct the realbits value to 16 to accurately reflect the hardware.  
> 
> > Tested on an SX9324-based device: a phase 0 DIFF readback of 0x7fff
> > was reported as -1 before this change and as 32767 afterward.  
> 
> Yeah, there seems only Chromebook devices (in ACPI world), MediaTek and
> Qualcomm (in DT world). Do we have anybody from Qualcomm to test this?
> 
> Hans, I think you (or somebody you might know at QCOMM) might be interested
> in this fix.

Looks like the actual dtsi blobs were all from google.
+CC Joseph on off chance still involved.

Applied the patch to the fixes-togreg branch of iio.git.
Note I'll rebase that on rc1 once available.

Jonathan

> 
> From the datasheet shared I see the same as described in this commit
> and since it was tested on real devices I'm quite sure this is the case.
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> 
> > Fixes: 4c18a890dff8 ("iio:proximity:sx9324: Add SX9324 support")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Zhang Jie <zhangjie14@huaqin.corp-partner.google.com>
> > ---
> >  drivers/iio/proximity/sx9324.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iio/proximity/sx9324.c b/drivers/iio/proximity/sx9324.c
> > index 36c45d101336..de6176fd8d47 100644
> > --- a/drivers/iio/proximity/sx9324.c
> > +++ b/drivers/iio/proximity/sx9324.c
> > @@ -223,7 +223,7 @@ static const struct iio_chan_spec_ext_info sx9324_channel_ext_info[] = {
> >  	.scan_index = idx,					 \
> >  	.scan_type = {						 \
> >  		.sign = 's',					 \
> > -		.realbits = 12,					 \
> > +		.realbits = 16,					 \
> >  		.storagebits = 16,				 \
> >  		.endianness = IIO_BE,				 \
> >  	},							 \  
>