From 347d7e45bd09ce09cbc30d5cea9de377eb22f55c Mon Sep 17 00:00:00 2001 From: "Stevens, Nick" Date: Wed, 1 Jul 2015 16:07:41 +0000 Subject: [PATCH] hwmon: (mcp3021) Fix broken output scaling 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 Cc: stable@vger.kernel.org # v3.10+ [Guenter Roeck: Dropped unnecessary value check] Signed-off-by: Guenter Roeck --- drivers/hwmon/mcp3021.c | 14 +------------- 1 file changed, 1 insertion(+), 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; } -- 2.34.1