linux-kernel - Re: [PATCH] drivers: iio: pressure: Add SPI support for BMP38x and BMP390

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Message-ID: <20240216164036.GA4230@vamoiridPC>
Date: Fri, 16 Feb 2024 17:40:36 +0100
From: Vasileios Amoiridis <vassilisamir@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Vasileios Amoiridis <vassilisamir@...il.com>, lars@...afoo.de,
	ang.iglesiasg@...il.com, andriy.shevchenko@...ux.intel.com,
	579lpy@...il.com, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: iio: pressure: Add SPI support for BMP38x and
 BMP390

On Fri, Feb 16, 2024 at 03:47:42PM +0000, Jonathan Cameron wrote:
> On Fri, 16 Feb 2024 14:26:44 +0100
> Vasileios Amoiridis <vassilisamir@...il.com> wrote:
> 
> > On Fri, Feb 16, 2024 at 11:18:34AM +0000, Jonathan Cameron wrote:
> > > On Thu, 15 Feb 2024 17:43:32 +0100
> > > Vasileios Amoiridis <vassilisamir@...il.com> wrote:
> > >   
> > > > According to the datasheet of BMP38x and BMP390 devices, in SPI
> > > > operation, the first byte that returns after a read operation is
> > > > garbage and it needs to be dropped and return the rest of the
> > > > bytes.  
> > > 
> > > Make it clear in the patch title that this is a fix and add a fixes tag.
> > >   
> > 
> > The original support for SPI was added 8 years ago. Should I include that commit
> > of 8 years ago in the fixes tag or just use a the word "fixes" with the rest of the
> > title?
> > 
> Original git commit for the fixes tag.  Lets us know this wants to go in all stable kernels.
> Also fixes in the title.
 
Ok, will do that!
>
> 
> > > > +	ssize_t status;
> > > > +	u8 buf;
> > > > +
> > > > +	memcpy(&buf, reg, reg_size);
> > > > +	buf |= 0x80;  
> > > 
> > > Can you use regmap_bus read_flag_mask for this?  Seems to apply to 
> > > all devices supported. + that's common for spi regmaps
> > >  
> > 
> > Yes I noticed it yesterday in my tests that this was missing and it actually
> > applies to all the devices. So the read_flag_mask should be added to both
> > regmap_bus structs. 
> 
> It's there sort of indirectly for the bmp280 - the register addresses all happen
> to include that bit, then it is cleared explicitly for the other direction.

Oh okay, now I understand what you mean. Ok then I can also send a different patch
for this as well just to keep the code consistent.
> 
> 
> 
> > > 
> > > Mind you I note the bmp280_regmap_spi_write() is masking the bit out which seems
> > > backwards  - all the registers are defined with the bit set for that part
> > > but not the 380.  Ah well - not part of this fix even if it's odd.
> > > 
> 
> > > > diff --git a/drivers/iio/pressure/bmp280.h b/drivers/iio/pressure/bmp280.h
> > > > index 4012387d7956..ca482b7e4295 100644
> > > > --- a/drivers/iio/pressure/bmp280.h
> > > > +++ b/drivers/iio/pressure/bmp280.h
> > > > @@ -191,6 +191,8 @@
> > > >  #define BMP380_TEMP_SKIPPED		0x800000
> > > >  #define BMP380_PRESS_SKIPPED		0x800000
> > > >  
> > > > +#define BMP380_SPI_MAX_REG_COUNT_READ   3  
> > > This doesn't seem useful as only used in one place.  
> > 
> > Could this define be moved in the bmp280-spi.c file or to not even use a define?
> Not use it. Don't see how it is helpful. Just check that the
> thing will fit in the array using an ARRAY_SIZE()...

Understood.
> > 
> > > > +
> > > >  /* BMP280 specific registers */
> > > >  #define BMP280_REG_HUMIDITY_LSB		0xFE
> > > >  #define BMP280_REG_HUMIDITY_MSB		0xFD  
> > >   
> 

Thank you very much for the feedback, I'll work on the patches and submit them again.

Best regards,
Vasileios Amoiridis