hw/i2c: Added linear mode translation for pmbus devices

Signed-off-by: Shengtan Mao <stmao@google.com>
Reviewed-by: Titus Rwantare <titusr@google.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: Corey Minyard <cminyard@mvista.com>
Message-Id: <20220307200605.4001451-7-titusr@google.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

2 files changed, 37 insertions, 1 deletions

diff --git a/hw/i2c/pmbus_device.c b/hw/i2c/pmbus_device.c
index 8cb9db0f80..62885fa6a1 100644
--- a/hw/i2c/pmbus_device.c
+++ b/hw/i2c/pmbus_device.c
@@ -28,6 +28,24 @@ uint32_t pmbus_direct_mode2data(PMBusCoefficients c, uint16_t value)
     return x;
 }
 
+uint16_t pmbus_data2linear_mode(uint16_t value, int exp)
+{
+    /* L = D * 2^(-e) */
+    if (exp < 0) {
+        return value << (-exp);
+    }
+    return value >> exp;
+}
+
+uint16_t pmbus_linear_mode2data(uint16_t value, int exp)
+{
+    /* D = L * 2^e */
+    if (exp < 0) {
+        return value >> (-exp);
+    }
+    return value << exp;
+}
+
 void pmbus_send(PMBusDevice *pmdev, const uint8_t *data, uint16_t len)
 {
     if (pmdev->out_buf_len + len > SMBUS_DATA_MAX_LEN) {
diff --git a/include/hw/i2c/pmbus_device.h b/include/hw/i2c/pmbus_device.h
index bab4526734..0f4d6b3fad 100644
--- a/include/hw/i2c/pmbus_device.h
+++ b/include/hw/i2c/pmbus_device.h
@@ -448,7 +448,7 @@ typedef struct PMBusCoefficients {
  *
  * Y = (m * x - b) * 10^R
  *
- * @return uint32_t
+ * @return uint16_t
  */
 uint16_t pmbus_data2direct_mode(PMBusCoefficients c, uint32_t value);
 
@@ -462,6 +462,24 @@ uint16_t pmbus_data2direct_mode(PMBusCoefficients c, uint32_t value);
 uint32_t pmbus_direct_mode2data(PMBusCoefficients c, uint16_t value);
 
 /**
+ * Convert sensor values to linear mode format
+ *
+ * L = D * 2^(-e)
+ *
+ * @return uint16
+ */
+uint16_t pmbus_data2linear_mode(uint16_t value, int exp);
+
+/**
+ * Convert linear mode formatted data into sensor reading
+ *
+ * D = L * 2^e
+ *
+ * @return uint16
+ */
+uint16_t pmbus_linear_mode2data(uint16_t value, int exp);
+
+/**
  * @brief Send a block of data over PMBus
  * Assumes that the bytes in the block are already ordered correctly,
  * also assumes the length has been prepended to the block if necessary