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[198.48.202.89]) by smtp.gmail.com with ESMTPSA id w2sm2521850qkm.65.2021.07.09.07.25.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 Jul 2021 07:25:12 -0700 (PDT) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 09 Jul 2021 10:25:11 -0400 Message-Id: From: "Liam Beguin" To: "Sa, Nuno" , "lars@metafoo.de" , "Hennerich, Michael" , "jic23@kernel.org" , "charles-antoine.couret@essensium.com" Cc: "linux-kernel@vger.kernel.org" , "linux-iio@vger.kernel.org" , "devicetree@vger.kernel.org" , "robh+dt@kernel.org" Subject: RE: [PATCH v1 2/4] iio: adc: ad7949: fix spi messages on non 14-bit controllers References: <20210708235618.1541335-1-liambeguin@gmail.com> <20210708235618.1541335-3-liambeguin@gmail.com> In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Fri Jul 9, 2021 at 4:19 AM EDT, Sa, Nuno wrote: > > > > -----Original Message----- > > From: Liam Beguin > > Sent: Friday, July 9, 2021 1:56 AM > > To: liambeguin@gmail.com; lars@metafoo.de; Hennerich, Michael > > ; jic23@kernel.org; charles- > > antoine.couret@essensium.com > > Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org; > > devicetree@vger.kernel.org; robh+dt@kernel.org > > Subject: [PATCH v1 2/4] iio: adc: ad7949: fix spi messages on non 14-bi= t > > controllers > >=20 > > [External] > >=20 > > From: Liam Beguin > >=20 > > This driver supports devices with 14-bit and 16-bit sample sizes. > > This is not always handled properly by spi controllers and can fail. To > > work around this limitation, pad samples to 16-bit and split the sample > > into two 8-bit messages in the event that only 8-bit messages are > > supported by the controller. > >=20 > > Signed-off-by: Liam Beguin > > --- > > drivers/iio/adc/ad7949.c | 67 > > ++++++++++++++++++++++++++++++++++------ > > 1 file changed, 58 insertions(+), 9 deletions(-) > >=20 > > diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c > > index 93aacf4f680b..bbc6b56330a3 100644 > > --- a/drivers/iio/adc/ad7949.c > > +++ b/drivers/iio/adc/ad7949.c > > @@ -11,6 +11,7 @@ > > #include > > #include > > #include > > +#include > >=20 > > #define AD7949_MASK_TOTAL GENMASK(13, 0) > > #define AD7949_CFG_REG_SIZE_BITS 14 > > @@ -57,6 +58,7 @@ static const struct ad7949_adc_spec > > ad7949_adc_spec[] =3D { > > * @indio_dev: reference to iio structure > > * @spi: reference to spi structure > > * @resolution: resolution of the chip > > + * @bits_per_word: number of bits per SPI word > > * @cfg: copy of the configuration register > > * @current_channel: current channel in use > > * @buffer: buffer to send / receive data to / from device > > @@ -67,28 +69,59 @@ struct ad7949_adc_chip { > > struct iio_dev *indio_dev; > > struct spi_device *spi; > > u8 resolution; > > + u8 bits_per_word; > > u16 cfg; > > unsigned int current_channel; > > - u16 buffer ____cacheline_aligned; > > + union { > > + __be16 buffer; > > + u8 buf8[2]; > > + } ____cacheline_aligned; > > }; > >=20 > > +static void ad7949_set_bits_per_word(struct ad7949_adc_chip > > *ad7949_adc) > > +{ > > + u32 adc_mask =3D SPI_BPW_MASK(ad7949_adc->resolution); > > + u32 bpw =3D adc_mask & ad7949_adc->spi->controller- > > >bits_per_word_mask; > > + > > + if (bpw =3D=3D adc_mask) > > + ad7949_adc->bits_per_word =3D ad7949_adc- > > >resolution; > > + else if (bpw =3D=3D SPI_BPW_MASK(16)) > > + ad7949_adc->bits_per_word =3D 16; > > + else > > + ad7949_adc->bits_per_word =3D 8; > > +} > > + > > static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, > > u16 val, > > u16 mask) > > { > > int ret; > > - int bits_per_word =3D ad7949_adc->resolution; > > - int shift =3D bits_per_word - AD7949_CFG_REG_SIZE_BITS; > > struct spi_message msg; > > struct spi_transfer tx[] =3D { > > { > > .tx_buf =3D &ad7949_adc->buffer, > > .len =3D 2, > > - .bits_per_word =3D bits_per_word, > > + .bits_per_word =3D ad7949_adc->bits_per_word, > > }, > > }; > >=20 > > + ad7949_adc->buffer =3D 0; > > ad7949_adc->cfg =3D (val & mask) | (ad7949_adc->cfg & ~mask); > > - ad7949_adc->buffer =3D ad7949_adc->cfg << shift; > > + > > + switch (ad7949_adc->bits_per_word) { > > + case 16: > > + ad7949_adc->buffer =3D ad7949_adc->cfg << 2; > > + break; > > + case 14: > > + ad7949_adc->buffer =3D ad7949_adc->cfg; > > + break; > > + case 8: > > + /* Pack 14-bit value into 2 bytes, MSB first */ > > + ad7949_adc->buf8[0] =3D FIELD_GET(GENMASK(13, 6), > > ad7949_adc->cfg); > > + ad7949_adc->buf8[1] =3D FIELD_GET(GENMASK(5, 0), > > ad7949_adc->cfg); > > + ad7949_adc->buf8[1] =3D ad7949_adc->buf8[1] << 2; > > + break; > > + } > > Honestly I didn't went through the driver but just a question... Are we > sure that 'ad7949_adc->resolution' will have something valid (8, 14, > 16)? > A default statement is always a nice to have :). > =20 Thanks for pointing that out. You're right that based on this driver there's no guaranty that `ad7949_adc->resolution` will have a valid value. I'll add a default to 8-bit. Thanks, Liam > > spi_message_init_with_transfers(&msg, tx, 1); > > ret =3D spi_sync(ad7949_adc->spi, &msg); > >=20 > > @@ -105,14 +138,12 @@ static int ad7949_spi_read_channel(struct > > ad7949_adc_chip *ad7949_adc, int *val, > > { > > int ret; > > int i; > > - int bits_per_word =3D ad7949_adc->resolution; > > - int mask =3D GENMASK(ad7949_adc->resolution - 1, 0); > > struct spi_message msg; > > struct spi_transfer tx[] =3D { > > { > > .rx_buf =3D &ad7949_adc->buffer, > > .len =3D 2, > > - .bits_per_word =3D bits_per_word, > > + .bits_per_word =3D ad7949_adc->bits_per_word, > > }, > > }; > >=20 > > @@ -147,7 +178,24 @@ static int ad7949_spi_read_channel(struct > > ad7949_adc_chip *ad7949_adc, int *val, > >=20 > > ad7949_adc->current_channel =3D channel; > >=20 > > - *val =3D ad7949_adc->buffer & mask; > > + switch (ad7949_adc->bits_per_word) { > > + case 16: > > + *val =3D ad7949_adc->buffer; > > + /* Shift-out padding bits */ > > + if (ad7949_adc->resolution =3D=3D 14) > > + *val =3D *val >> 2; > > + break; > > + case 14: > > + *val =3D ad7949_adc->buffer & GENMASK(13, 0); > > + break; > > + case 8: > > + /* Convert byte array to u16, MSB first */ > > + *val =3D (ad7949_adc->buf8[0] << 8) | ad7949_adc- > > >buf8[1]; > > + /* Shift-out padding bits */ > > + if (ad7949_adc->resolution =3D=3D 14) > > + *val =3D *val >> 2; > > + break; > > + } > >=20 > > return 0; > > } > > @@ -280,6 +328,7 @@ static int ad7949_spi_probe(struct spi_device > > *spi) > > spec =3D &ad7949_adc_spec[spi_get_device_id(spi)- > > >driver_data]; > > indio_dev->num_channels =3D spec->num_channels; > > ad7949_adc->resolution =3D spec->resolution; > > + ad7949_set_bits_per_word(ad7949_adc); > >=20 > > ad7949_adc->vref =3D devm_regulator_get(dev, "vref"); > > if (IS_ERR(ad7949_adc->vref)) { > > -- > > 2.30.1.489.g328c10930387