On Sun, 15 Aug 2021 17:33:06 -0400
Liam Beguin <liambeguin@xxxxxxxxx> wrote:
> From: Liam Beguin <lvb@xxxxxxxxxx>
>
> This driver supports devices with 14-bit and 16-bit sample sizes.
> This implies different SPI transfer lengths which are not always handled
> properly by some SPI controllers.
>
> To work around this limitation, define a big endian buffer used to split
> the buffer into two 8-bit messages in the event that the controller
> doesn't support 14-bit or 16-bit transfers.
> A separate buffer is introduced here to avoid performing operations on
> types of different endianness.
>
> Since all transfers use the same bits_per_word value, move that logic to
> the probe function, and let transfers default to the value defined in
> the struct spi_device.
>
> Signed-off-by: Liam Beguin <lvb@xxxxxxxxxx>
Hi Liam,
I changed the title of this one to avoid it being picked up for automated
backporting. I don't mind if you want to request it is backported explicitly
but it isn't a regression fix (as it never worked on such controllers) and
is non trivial. As a result I want a backport to be a deliberate decision.
Now titled "iio: adc: ad7949: enable use with non 14/16-bit controllers"
This and previous applied to the togreg branch of iio.git and pushed out
as testing for 0-day to poke at it.
Thanks,
Jonathan
> ---
> drivers/iio/adc/ad7949.c | 86 +++++++++++++++++++++++++++-------------
> 1 file changed, 58 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> index adc4487a7d56..a263d0fcec75 100644
> --- a/drivers/iio/adc/ad7949.c
> +++ b/drivers/iio/adc/ad7949.c
> @@ -14,7 +14,6 @@
> #include <linux/bitfield.h>
>
> #define AD7949_CFG_MASK_TOTAL GENMASK(13, 0)
> -#define AD7949_CFG_REG_SIZE_BITS 14
>
> /* CFG: Configuration Update */
> #define AD7949_CFG_MASK_OVERWRITE BIT(13)
> @@ -71,6 +70,7 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
> * @cfg: copy of the configuration register
> * @current_channel: current channel in use
> * @buffer: buffer to send / receive data to / from device
> + * @buf8b: be16 buffer to exchange data with the device in 8-bit transfers
> */
> struct ad7949_adc_chip {
> struct mutex lock;
> @@ -81,27 +81,34 @@ struct ad7949_adc_chip {
> u16 cfg;
> unsigned int current_channel;
> u16 buffer ____cacheline_aligned;
> + __be16 buf8b;
> };
>
> static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
> u16 mask)
> {
> int ret;
> - int bits_per_word = ad7949_adc->resolution;
> - int shift = bits_per_word - AD7949_CFG_REG_SIZE_BITS;
> - struct spi_message msg;
> - struct spi_transfer tx[] = {
> - {
> - .tx_buf = &ad7949_adc->buffer,
> - .len = 2,
> - .bits_per_word = bits_per_word,
> - },
> - };
>
> ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);
> - ad7949_adc->buffer = ad7949_adc->cfg << shift;
> - spi_message_init_with_transfers(&msg, tx, 1);
> - ret = spi_sync(ad7949_adc->spi, &msg);
> +
> + switch (ad7949_adc->spi->bits_per_word) {
> + case 16:
> + ad7949_adc->buffer = ad7949_adc->cfg << 2;
> + ret = spi_write(ad7949_adc->spi, &ad7949_adc->buffer, 2);
> + break;
> + case 14:
> + ad7949_adc->buffer = ad7949_adc->cfg;
> + ret = spi_write(ad7949_adc->spi, &ad7949_adc->buffer, 2);
> + break;
> + case 8:
> + /* Here, type is big endian as it must be sent in two transfers */
> + ad7949_adc->buf8b = cpu_to_be16(ad7949_adc->cfg << 2);
> + ret = spi_write(ad7949_adc->spi, &ad7949_adc->buf8b, 2);
> + break;
> + default:
> + dev_err(&ad7949_adc->indio_dev->dev, "unsupported BPW\n");
> + return -EINVAL;
> + }
>
> /*
> * This delay is to avoid a new request before the required time to
> @@ -116,16 +123,6 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
> {
> int ret;
> int i;
> - int bits_per_word = ad7949_adc->resolution;
> - int mask = GENMASK(ad7949_adc->resolution - 1, 0);
> - struct spi_message msg;
> - struct spi_transfer tx[] = {
> - {
> - .rx_buf = &ad7949_adc->buffer,
> - .len = 2,
> - .bits_per_word = bits_per_word,
> - },
> - };
>
> /*
> * 1: write CFG for sample N and read old data (sample N-2)
> @@ -144,9 +141,11 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
> }
>
> /* 3: write something and read actual data */
> - ad7949_adc->buffer = 0;
> - spi_message_init_with_transfers(&msg, tx, 1);
> - ret = spi_sync(ad7949_adc->spi, &msg);
> + if (ad7949_adc->spi->bits_per_word == 8)
> + ret = spi_read(ad7949_adc->spi, &ad7949_adc->buf8b, 2);
> + else
> + ret = spi_read(ad7949_adc->spi, &ad7949_adc->buffer, 2);
> +
> if (ret)
> return ret;
>
> @@ -158,7 +157,25 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
>
> ad7949_adc->current_channel = channel;
>
> - *val = ad7949_adc->buffer & mask;
> + switch (ad7949_adc->spi->bits_per_word) {
> + case 16:
> + *val = ad7949_adc->buffer;
> + /* Shift-out padding bits */
> + *val >>= 16 - ad7949_adc->resolution;
> + break;
> + case 14:
> + *val = ad7949_adc->buffer & GENMASK(13, 0);
> + break;
> + case 8:
> + /* Here, type is big endian as data was sent in two transfers */
> + *val = be16_to_cpu(ad7949_adc->buf8b);
> + /* Shift-out padding bits */
> + *val >>= 16 - ad7949_adc->resolution;
> + break;
> + default:
> + dev_err(&ad7949_adc->indio_dev->dev, "unsupported BPW\n");
> + return -EINVAL;
> + }
>
> return 0;
> }
> @@ -266,6 +283,7 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
>
> static int ad7949_spi_probe(struct spi_device *spi)
> {
> + u32 spi_ctrl_mask = spi->controller->bits_per_word_mask;
> struct device *dev = &spi->dev;
> const struct ad7949_adc_spec *spec;
> struct ad7949_adc_chip *ad7949_adc;
> @@ -292,6 +310,18 @@ static int ad7949_spi_probe(struct spi_device *spi)
> indio_dev->num_channels = spec->num_channels;
> ad7949_adc->resolution = spec->resolution;
>
> + /* Set SPI bits per word */
> + if (spi_ctrl_mask & SPI_BPW_MASK(ad7949_adc->resolution)) {
> + spi->bits_per_word = ad7949_adc->resolution;
> + } else if (spi_ctrl_mask == SPI_BPW_MASK(16)) {
> + spi->bits_per_word = 16;
> + } else if (spi_ctrl_mask == SPI_BPW_MASK(8)) {
> + spi->bits_per_word = 8;
> + } else {
> + dev_err(dev, "unable to find common BPW with spi controller\n");
> + return -EINVAL;
> + }
> +
> ad7949_adc->vref = devm_regulator_get(dev, "vref");
> if (IS_ERR(ad7949_adc->vref)) {
> dev_err(dev, "fail to request regulator\n");
