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| author | Nicholas Troast <ntroast@codeaurora.org> | 2016-08-25 10:59:21 -0700 |
|---|---|---|
| committer | Nicholas Troast <ntroast@codeaurora.org> | 2016-09-27 19:55:54 -0700 |
| commit | 9d4164b5e808c3d45a19ef803d5eaf0df0a4faf3 (patch) | |
| tree | 5164f0487d2e7c61ed1cddb09f0d64933649bbac | |
| parent | 654b1238efbf670034721649b9fd5ad5b4f0fad6 (diff) | |
qcom-charger: fg-util: add float decode function
Some SRAM registers are encoded using a floating point representation.
Add a function to decode these registers into signed micro-unit
integers.
The exponent and mantissa are signed integers represented by two's
complement, and the exponent value is offset by -9. This is a half
float representation stored as:
EEEEE MMMMMMMMMMM
Where E are the exponent bits, and M are the mantissa bits.
To decode this representation the following formula is applied:
2^(exponent - 9) * mantissa
Change-Id: Id9f28a0eeb2a904aca41eb46d0215d80287e0b88
Signed-off-by: Nicholas Troast <ntroast@codeaurora.org>
| -rw-r--r-- | drivers/power/qcom-charger/fg-core.h | 1 | ||||
| -rw-r--r-- | drivers/power/qcom-charger/fg-util.c | 20 |
2 files changed, 21 insertions, 0 deletions
diff --git a/drivers/power/qcom-charger/fg-core.h b/drivers/power/qcom-charger/fg-core.h index 08ec7334737e..a609d8fcd400 100644 --- a/drivers/power/qcom-charger/fg-core.h +++ b/drivers/power/qcom-charger/fg-core.h @@ -252,4 +252,5 @@ extern int fg_ima_init(struct fg_chip *chip); extern int fg_sram_debugfs_create(struct fg_chip *chip); extern void fill_string(char *str, size_t str_len, u8 *buf, int buf_len); extern int64_t twos_compliment_extend(int64_t val, int s_bit_pos); +extern s64 fg_float_decode(u16 val); #endif diff --git a/drivers/power/qcom-charger/fg-util.c b/drivers/power/qcom-charger/fg-util.c index 5f133d6f39c1..0d52fb5ba9b8 100644 --- a/drivers/power/qcom-charger/fg-util.c +++ b/drivers/power/qcom-charger/fg-util.c @@ -29,6 +29,26 @@ static struct fg_dbgfs dbgfs_data = { }, }; +#define EXPONENT_SHIFT 11 +#define EXPONENT_OFFSET -9 +#define MANTISSA_SIGN_BIT 10 +#define MICRO_UNIT 1000000 +s64 fg_float_decode(u16 val) +{ + s8 exponent; + s32 mantissa; + + /* mantissa bits are shifted out during sign extension */ + exponent = ((s16)val >> EXPONENT_SHIFT) + EXPONENT_OFFSET; + /* exponent bits are shifted out during sign extension */ + mantissa = sign_extend32(val, MANTISSA_SIGN_BIT) * MICRO_UNIT; + + if (exponent < 0) + return (s64)mantissa >> -exponent; + + return (s64)mantissa << exponent; +} + void fill_string(char *str, size_t str_len, u8 *buf, int buf_len) { int pos = 0; |