drm/xe/hwmon: Cast result to output precision on left shift of operand

Address potential overflow in result of left shift of a
lower precision (u32) operand before assignment to higher
precision (u64) variable.

v2:
 - Update commit message. (Himal)

Fixes: 4446fcf ("drm/xe/hwmon: Expose power1_max_interval")
Signed-off-by: Karthik Poosa <[email protected]>
Reviewed-by: Anshuman Gupta <[email protected]>
Cc: Badal Nilawar <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Lucas De Marchi <[email protected]>

Author: kpoosa

drivers/gpu/drm/xe/xe_hwmon.c

@@ -298,7 +298,7 @@ xe_hwmon_power_max_interval_show(struct device *dev, struct device_attribute *at
 	 * As y can be < 2, we compute tau4 = (4 | x) << y
 	 * and then add 2 when doing the final right shift to account for units
 	 */
-	tau4 = ((1 << x_w) | x) << y;
+	tau4 = (u64)((1 << x_w) | x) << y;
 
 	/* val in hwmon interface units (millisec) */
 	out = mul_u64_u32_shr(tau4, SF_TIME, hwmon->scl_shift_time + x_w);
@@ -339,7 +339,7 @@ xe_hwmon_power_max_interval_store(struct device *dev, struct device_attribute *a
 	r = FIELD_PREP(PKG_MAX_WIN, PKG_MAX_WIN_DEFAULT);
 	x = REG_FIELD_GET(PKG_MAX_WIN_X, r);
 	y = REG_FIELD_GET(PKG_MAX_WIN_Y, r);
-	tau4 = ((1 << x_w) | x) << y;
+	tau4 = (u64)((1 << x_w) | x) << y;
 	max_win = mul_u64_u32_shr(tau4, SF_TIME, hwmon->scl_shift_time + x_w);
 
 	if (val > max_win)