diff options
| author | Stevens, Nick <Nick.Stevens@digi.com> | 2015-07-01 16:07:41 +0000 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2015-08-04 16:52:24 +0200 |
| commit | dab00c734ec3fe7bd5ed0ececf6c6b5339d74075 (patch) | |
| tree | 86620f99d72d2173e7bd8ebcca6e502e1593e195 | |
| parent | 0c07c995fbb0c3f44b7f4b472a8b750e684d8585 (diff) | |
hwmon: (mcp3021) Fix broken output scaling
commit 347d7e45bd09ce09cbc30d5cea9de377eb22f55c upstream.
The mcp3021 scaling code is dividing the VDD (full-scale) value in
millivolts by the A2D resolution to obtain the scaling factor. When VDD
is 3300mV (the standard value) and the resolution is 12-bit (4096
divisions), the result is a scale factor of 3300/4096, which is always
one. Effectively, the raw A2D reading is always being returned because
no scaling is applied.
This patch fixes the issue and simplifies the register-to-volts
calculation, removing the unneeded "output_scale" struct member.
Signed-off-by: Nick Stevens <Nick.Stevens@digi.com>
[Guenter Roeck: Dropped unnecessary value check]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
| -rw-r--r-- | drivers/hwmon/mcp3021.c | 14 |
1 files changed, 1 insertions, 13 deletions
diff --git a/drivers/hwmon/mcp3021.c b/drivers/hwmon/mcp3021.c index d219c06a857b..972444a14cca 100644 --- a/drivers/hwmon/mcp3021.c +++ b/drivers/hwmon/mcp3021.c @@ -31,14 +31,11 @@ /* output format */ #define MCP3021_SAR_SHIFT 2 #define MCP3021_SAR_MASK 0x3ff - #define MCP3021_OUTPUT_RES 10 /* 10-bit resolution */ -#define MCP3021_OUTPUT_SCALE 4 #define MCP3221_SAR_SHIFT 0 #define MCP3221_SAR_MASK 0xfff #define MCP3221_OUTPUT_RES 12 /* 12-bit resolution */ -#define MCP3221_OUTPUT_SCALE 1 enum chips { mcp3021, @@ -54,7 +51,6 @@ struct mcp3021_data { u16 sar_shift; u16 sar_mask; u8 output_res; - u8 output_scale; }; static int mcp3021_read16(struct i2c_client *client) @@ -84,13 +80,7 @@ static int mcp3021_read16(struct i2c_client *client) static inline u16 volts_from_reg(struct mcp3021_data *data, u16 val) { - if (val == 0) - return 0; - - val = val * data->output_scale - data->output_scale / 2; - - return val * DIV_ROUND_CLOSEST(data->vdd, - (1 << data->output_res) * data->output_scale); + return DIV_ROUND_CLOSEST(data->vdd * val, 1 << data->output_res); } static ssize_t show_in_input(struct device *dev, struct device_attribute *attr, @@ -132,14 +122,12 @@ static int mcp3021_probe(struct i2c_client *client, data->sar_shift = MCP3021_SAR_SHIFT; data->sar_mask = MCP3021_SAR_MASK; data->output_res = MCP3021_OUTPUT_RES; - data->output_scale = MCP3021_OUTPUT_SCALE; break; case mcp3221: data->sar_shift = MCP3221_SAR_SHIFT; data->sar_mask = MCP3221_SAR_MASK; data->output_res = MCP3221_OUTPUT_RES; - data->output_scale = MCP3221_OUTPUT_SCALE; break; } |