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Date:   Wed, 6 Mar 2019 07:27:52 +0000
From:   Mike Looijmans <mike.looijmans@...ic.nl>
To:     Jonathan Cameron <jic23@...nel.org>
CC:     "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "himanshujha199640@...il.com" <himanshujha199640@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "knaack.h@....de" <knaack.h@....de>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "pmeerw@...erw.net" <pmeerw@...erw.net>,
        "dpfrey@...il.com" <dpfrey@...il.com>,
        "colin.king@...onical.com" <colin.king@...onical.com>
Subject: Re: [PATCH v2] iio/chemical/bme680: Fix SPI read interface

On 03-03-19 17:57, Jonathan Cameron wrote:
> On Thu, 21 Feb 2019 10:20:49 +0100
> Mike Looijmans <mike.looijmans@...ic.nl> wrote:
> 
>> The SPI interface implementation was completely broken.
>>
>> When using the SPI interface, there are only 7 address bits, the upper bit
>> is controlled by a page select register. The core needs access to both
>> ranges, so implement register read/write for both regions. The regmap
>> paging functionality didn't agree with a register that needs to be read
>> and modified, so I implemented a custom paging algorithm.
>>
>> This fixes that the device wouldn't even probe in SPI mode.
>>
>> The SPI interface then isn't different from I2C, merged them into the core,
>> and the I2C/SPI named registers are no longer needed.
>>
>> Implemented register value caching for the registers to reduce the I2C/SPI
>> data transfers considerably.
>>
>> The calibration set reads as all zeroes until some undefined point in time,
>> and I couldn't determine what makes it valid. The datasheet mentions these
>> registers but does not provide any hints on when they become valid, and they
>> aren't even enumerated in the memory map. So check the calibration and
>> retry reading it from the device after each measurement until it provides
>> something valid.
>>
>> Report temperature in millidegrees Celcius instead of degrees.
> Hi Mike,
> 
> This last bit is an unrelated issue. Would you mind splitting the patch into two?
> Please put the temperature one first as that is definitely a stable
> worthy patch.  The larger one is more debatable as it seems that it
> never worked and is a fairly large patch.
> 
> I'll probably mark them both for stable, but it is possible not all
> the stable branches will pick them both up.

Splitting the patch was easy enough, the're independent, I'll post a v3 with 
both patches.


> 
> Thanks,
> 
> Jonathan
> 
>>
>> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
>> ---
>> v2: Remove unused 'addr7' variable
>>
>>   drivers/iio/chemical/bme680.h      |   6 +-
>>   drivers/iio/chemical/bme680_core.c |  54 ++++++++++++++---
>>   drivers/iio/chemical/bme680_i2c.c  |  21 -------
>>   drivers/iio/chemical/bme680_spi.c  | 115 +++++++++++++++++++++++++------------
>>   4 files changed, 125 insertions(+), 71 deletions(-)
>>
>> diff --git a/drivers/iio/chemical/bme680.h b/drivers/iio/chemical/bme680.h
>> index 0ae89b87..4edc5d21 100644
>> --- a/drivers/iio/chemical/bme680.h
>> +++ b/drivers/iio/chemical/bme680.h
>> @@ -2,11 +2,9 @@
>>   #ifndef BME680_H_
>>   #define BME680_H_
>>   
>> -#define BME680_REG_CHIP_I2C_ID			0xD0
>> -#define BME680_REG_CHIP_SPI_ID			0x50
>> +#define BME680_REG_CHIP_ID			0xD0
>>   #define   BME680_CHIP_ID_VAL			0x61
>> -#define BME680_REG_SOFT_RESET_I2C		0xE0
>> -#define BME680_REG_SOFT_RESET_SPI		0x60
>> +#define BME680_REG_SOFT_RESET			0xE0
>>   #define   BME680_CMD_SOFTRESET			0xB6
>>   #define BME680_REG_STATUS			0x73
>>   #define   BME680_SPI_MEM_PAGE_BIT		BIT(4)
>> diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
>> index 70c1fe4..ccde4c6 100644
>> --- a/drivers/iio/chemical/bme680_core.c
>> +++ b/drivers/iio/chemical/bme680_core.c
>> @@ -63,9 +63,23 @@ struct bme680_data {
>>   	s32 t_fine;
>>   };
>>   
>> +static const struct regmap_range bme680_volatile_ranges[] = {
>> +	regmap_reg_range(BME680_REG_MEAS_STAT_0, BME680_REG_GAS_R_LSB),
>> +	regmap_reg_range(BME680_REG_STATUS, BME680_REG_STATUS),
>> +	regmap_reg_range(BME680_T2_LSB_REG, BME680_GH3_REG),
>> +};
>> +
>> +static const struct regmap_access_table bme680_volatile_table = {
>> +	.yes_ranges	= bme680_volatile_ranges,
>> +	.n_yes_ranges	= ARRAY_SIZE(bme680_volatile_ranges),
>> +};
>> +
>>   const struct regmap_config bme680_regmap_config = {
>>   	.reg_bits = 8,
>>   	.val_bits = 8,
>> +	.max_register = 0xef,
>> +	.volatile_table = &bme680_volatile_table,
>> +	.cache_type = REGCACHE_RBTREE,
>>   };
>>   EXPORT_SYMBOL(bme680_regmap_config);
>>   
>> @@ -316,6 +330,10 @@ static s16 bme680_compensate_temp(struct bme680_data *data,
>>   	s64 var1, var2, var3;
>>   	s16 calc_temp;
>>   
>> +	/* If the calibration is invalid, attempt to reload it */
>> +	if (!calib->par_t2)
>> +		bme680_read_calib(data, calib);
>> +
>>   	var1 = (adc_temp >> 3) - (calib->par_t1 << 1);
>>   	var2 = (var1 * calib->par_t2) >> 11;
>>   	var3 = ((var1 >> 1) * (var1 >> 1)) >> 12;
>> @@ -583,8 +601,7 @@ static int bme680_gas_config(struct bme680_data *data)
>>   	return ret;
>>   }
>>   
>> -static int bme680_read_temp(struct bme680_data *data,
>> -			    int *val, int *val2)
>> +static int bme680_read_temp(struct bme680_data *data, int *val)
>>   {
>>   	struct device *dev = regmap_get_device(data->regmap);
>>   	int ret;
>> @@ -617,10 +634,9 @@ static int bme680_read_temp(struct bme680_data *data,
>>   	 * compensate_press/compensate_humid to get compensated
>>   	 * pressure/humidity readings.
>>   	 */
>> -	if (val && val2) {
>> -		*val = comp_temp;
>> -		*val2 = 100;
>> -		return IIO_VAL_FRACTIONAL;
>> +	if (val) {
>> +		*val = comp_temp * 10; /* Centidegrees to millidegrees */
>> +		return IIO_VAL_INT;
>>   	}
>>   
>>   	return ret;
>> @@ -635,7 +651,7 @@ static int bme680_read_press(struct bme680_data *data,
>>   	s32 adc_press;
>>   
>>   	/* Read and compensate temperature to get a reading of t_fine */
>> -	ret = bme680_read_temp(data, NULL, NULL);
>> +	ret = bme680_read_temp(data, NULL);
>>   	if (ret < 0)
>>   		return ret;
>>   
>> @@ -668,7 +684,7 @@ static int bme680_read_humid(struct bme680_data *data,
>>   	u32 comp_humidity;
>>   
>>   	/* Read and compensate temperature to get a reading of t_fine */
>> -	ret = bme680_read_temp(data, NULL, NULL);
>> +	ret = bme680_read_temp(data, NULL);
>>   	if (ret < 0)
>>   		return ret;
>>   
>> @@ -761,7 +777,7 @@ static int bme680_read_raw(struct iio_dev *indio_dev,
>>   	case IIO_CHAN_INFO_PROCESSED:
>>   		switch (chan->type) {
>>   		case IIO_TEMP:
>> -			return bme680_read_temp(data, val, val2);
>> +			return bme680_read_temp(data, val);
>>   		case IIO_PRESSURE:
>>   			return bme680_read_press(data, val, val2);
>>   		case IIO_HUMIDITYRELATIVE:
>> @@ -867,8 +883,28 @@ int bme680_core_probe(struct device *dev, struct regmap *regmap,
>>   {
>>   	struct iio_dev *indio_dev;
>>   	struct bme680_data *data;
>> +	unsigned int val;
>>   	int ret;
>>   
>> +	ret = regmap_write(regmap, BME680_REG_SOFT_RESET,
>> +			   BME680_CMD_SOFTRESET);
>> +	if (ret < 0) {
>> +		dev_err(dev, "Failed to reset chip\n");
>> +		return ret;
>> +	}
>> +
>> +	ret = regmap_read(regmap, BME680_REG_CHIP_ID, &val);
>> +	if (ret < 0) {
>> +		dev_err(dev, "Error reading chip ID\n");
>> +		return ret;
>> +	}
>> +
>> +	if (val != BME680_CHIP_ID_VAL) {
>> +		dev_err(dev, "Wrong chip ID, got %x expected %x\n",
>> +				val, BME680_CHIP_ID_VAL);
>> +		return -ENODEV;
>> +	}
>> +
>>   	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
>>   	if (!indio_dev)
>>   		return -ENOMEM;
>> diff --git a/drivers/iio/chemical/bme680_i2c.c b/drivers/iio/chemical/bme680_i2c.c
>> index 06d4be5..cfc4449 100644
>> --- a/drivers/iio/chemical/bme680_i2c.c
>> +++ b/drivers/iio/chemical/bme680_i2c.c
>> @@ -23,8 +23,6 @@ static int bme680_i2c_probe(struct i2c_client *client,
>>   {
>>   	struct regmap *regmap;
>>   	const char *name = NULL;
>> -	unsigned int val;
>> -	int ret;
>>   
>>   	regmap = devm_regmap_init_i2c(client, &bme680_regmap_config);
>>   	if (IS_ERR(regmap)) {
>> @@ -33,25 +31,6 @@ static int bme680_i2c_probe(struct i2c_client *client,
>>   		return PTR_ERR(regmap);
>>   	}
>>   
>> -	ret = regmap_write(regmap, BME680_REG_SOFT_RESET_I2C,
>> -			   BME680_CMD_SOFTRESET);
>> -	if (ret < 0) {
>> -		dev_err(&client->dev, "Failed to reset chip\n");
>> -		return ret;
>> -	}
>> -
>> -	ret = regmap_read(regmap, BME680_REG_CHIP_I2C_ID, &val);
>> -	if (ret < 0) {
>> -		dev_err(&client->dev, "Error reading I2C chip ID\n");
>> -		return ret;
>> -	}
>> -
>> -	if (val != BME680_CHIP_ID_VAL) {
>> -		dev_err(&client->dev, "Wrong chip ID, got %x expected %x\n",
>> -				val, BME680_CHIP_ID_VAL);
>> -		return -ENODEV;
>> -	}
>> -
>>   	if (id)
>>   		name = id->name;
>>   
>> diff --git a/drivers/iio/chemical/bme680_spi.c b/drivers/iio/chemical/bme680_spi.c
>> index c9fb05e..881778e 100644
>> --- a/drivers/iio/chemical/bme680_spi.c
>> +++ b/drivers/iio/chemical/bme680_spi.c
>> @@ -11,28 +11,93 @@
>>   
>>   #include "bme680.h"
>>   
>> +struct bme680_spi_bus_context {
>> +	struct spi_device *spi;
>> +	u8 current_page;
>> +};
>> +
>> +/*
>> + * In SPI mode there are only 7 address bits, a "page" register determines
>> + * which part of the 8-bit range is active. This function looks at the address
>> + * and writes the page selection bit if needed
>> + */
>> +static int bme680_regmap_spi_select_page(
>> +	struct bme680_spi_bus_context *ctx, u8 reg)
>> +{
>> +	struct spi_device *spi = ctx->spi;
>> +	int ret;
>> +	u8 buf[2];
>> +	u8 page = (reg & 0x80) ? 0 : 1; /* Page "1" is low range */
>> +
>> +	if (page == ctx->current_page)
>> +		return 0;
>> +
>> +	/*
>> +	 * Data sheet claims we're only allowed to change bit 4, so we must do
>> +	 * a read-modify-write on each and every page select
>> +	 */
>> +	buf[0] = BME680_REG_STATUS;
>> +	ret = spi_write_then_read(spi, buf, 1, buf + 1, 1);
>> +	if (ret < 0) {
>> +		dev_err(&spi->dev, "failed to set page %u\n", page);
>> +		return ret;
>> +	}
>> +
>> +	buf[0] = BME680_REG_STATUS;
>> +	if (page)
>> +		buf[1] |= BME680_SPI_MEM_PAGE_BIT;
>> +	else
>> +		buf[1] &= ~BME680_SPI_MEM_PAGE_BIT;
>> +
>> +	ret = spi_write(spi, buf, 2);
>> +	if (ret < 0) {
>> +		dev_err(&spi->dev, "failed to set page %u\n", page);
>> +		return ret;
>> +	}
>> +
>> +	ctx->current_page = page;
>> +
>> +	return 0;
>> +}
>> +
>>   static int bme680_regmap_spi_write(void *context, const void *data,
>>   				   size_t count)
>>   {
>> -	struct spi_device *spi = context;
>> +	struct bme680_spi_bus_context *ctx = context;
>> +	struct spi_device *spi = ctx->spi;
>> +	int ret;
>>   	u8 buf[2];
>>   
>>   	memcpy(buf, data, 2);
>> +
>> +	ret = bme680_regmap_spi_select_page(ctx, buf[0]);
>> +	if (ret)
>> +		return ret;
>> +
>>   	/*
>>   	 * The SPI register address (= full register address without bit 7)
>>   	 * and the write command (bit7 = RW = '0')
>>   	 */
>>   	buf[0] &= ~0x80;
>>   
>> -	return spi_write_then_read(spi, buf, 2, NULL, 0);
>> +	return spi_write(spi, buf, 2);
>>   }
>>   
>>   static int bme680_regmap_spi_read(void *context, const void *reg,
>>   				  size_t reg_size, void *val, size_t val_size)
>>   {
>> -	struct spi_device *spi = context;
>> +	struct bme680_spi_bus_context *ctx = context;
>> +	struct spi_device *spi = ctx->spi;
>> +	int ret;
>> +	u8 addr = *(const u8 *)reg;
>> +
>> +	ret = bme680_regmap_spi_select_page(ctx, addr);
>> +	if (ret)
>> +		return ret;
>>   
>> -	return spi_write_then_read(spi, reg, reg_size, val, val_size);
>> +	addr |= 0x80; /* bit7 = RW = '1' */
>> +
>> +	return spi_write_then_read(spi, &addr, 1, val, val_size);
>>   }
>>   
>>   static struct regmap_bus bme680_regmap_bus = {
>> @@ -45,8 +110,8 @@ static int bme680_regmap_spi_read(void *context, const void *reg,
>>   static int bme680_spi_probe(struct spi_device *spi)
>>   {
>>   	const struct spi_device_id *id = spi_get_device_id(spi);
>> +	struct bme680_spi_bus_context *bus_context;
>>   	struct regmap *regmap;
>> -	unsigned int val;
>>   	int ret;
>>   
>>   	spi->bits_per_word = 8;
>> @@ -56,45 +121,21 @@ static int bme680_spi_probe(struct spi_device *spi)
>>   		return ret;
>>   	}
>>   
>> +	bus_context = devm_kzalloc(&spi->dev, sizeof(*bus_context), GFP_KERNEL);
>> +	if (!bus_context)
>> +		return -ENOMEM;
>> +
>> +	bus_context->spi = spi;
>> +	bus_context->current_page = 0xff; /* Undefined on warm boot */
>> +
>>   	regmap = devm_regmap_init(&spi->dev, &bme680_regmap_bus,
>> -				  &spi->dev, &bme680_regmap_config);
>> +				  bus_context, &bme680_regmap_config);
>>   	if (IS_ERR(regmap)) {
>>   		dev_err(&spi->dev, "Failed to register spi regmap %d\n",
>>   				(int)PTR_ERR(regmap));
>>   		return PTR_ERR(regmap);
>>   	}
>>   
>> -	ret = regmap_write(regmap, BME680_REG_SOFT_RESET_SPI,
>> -			   BME680_CMD_SOFTRESET);
>> -	if (ret < 0) {
>> -		dev_err(&spi->dev, "Failed to reset chip\n");
>> -		return ret;
>> -	}
>> -
>> -	/* after power-on reset, Page 0(0x80-0xFF) of spi_mem_page is active */
>> -	ret = regmap_read(regmap, BME680_REG_CHIP_SPI_ID, &val);
>> -	if (ret < 0) {
>> -		dev_err(&spi->dev, "Error reading SPI chip ID\n");
>> -		return ret;
>> -	}
>> -
>> -	if (val != BME680_CHIP_ID_VAL) {
>> -		dev_err(&spi->dev, "Wrong chip ID, got %x expected %x\n",
>> -				val, BME680_CHIP_ID_VAL);
>> -		return -ENODEV;
>> -	}
>> -	/*
>> -	 * select Page 1 of spi_mem_page to enable access to
>> -	 * to registers from address 0x00 to 0x7F.
>> -	 */
>> -	ret = regmap_write_bits(regmap, BME680_REG_STATUS,
>> -				BME680_SPI_MEM_PAGE_BIT,
>> -				BME680_SPI_MEM_PAGE_1_VAL);
>> -	if (ret < 0) {
>> -		dev_err(&spi->dev, "failed to set page 1 of spi_mem_page\n");
>> -		return ret;
>> -	}
>> -
>>   	return bme680_core_probe(&spi->dev, regmap, id->name);
>>   }
>>   
> 

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