[PATCH] drm/i915/hwmon: Don't use FIELD_PREP

[Ashutosh Dixit]

FIELD_PREP and REG_FIELD_PREP have checks requiring a compile time constant
mask. When the mask comes in as the argument of a function these checks can
can fail depending on the compiler (gcc vs clang), optimization level,
etc. Use a simpler local version of FIELD_PREP which skips these
checks. The checks are not needed because the mask is formed using
REG_GENMASK (so is actually a compile time constant).

Bug: https://gitlab.freedesktop.org/drm/intel/-/issues/7354
Signed-off-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
---
 drivers/gpu/drm/i915/i915_hwmon.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c
index 9e97814930254..a3ec9a73a4e49 100644
--- a/drivers/gpu/drm/i915/i915_hwmon.c
+++ b/drivers/gpu/drm/i915/i915_hwmon.c
@@ -62,6 +62,12 @@ struct i915_hwmon {
 	int scl_shift_time;
 };
 
+/* FIELD_PREP and REG_FIELD_PREP require a compile time constant mask */
+static u32 hwm_field_prep(u32 mask, u32 val)
+{
+	return (val << __bf_shf(mask)) & mask;
+}
+
 static void
 hwm_locked_with_pm_intel_uncore_rmw(struct hwm_drvdata *ddat,
 				    i915_reg_t reg, u32 clear, u32 set)
@@ -112,7 +118,7 @@ hwm_field_scale_and_write(struct hwm_drvdata *ddat, i915_reg_t rgadr,
 	nval = DIV_ROUND_CLOSEST_ULL((u64)lval << nshift, scale_factor);
 
 	bits_to_clear = field_msk;
-	bits_to_set = FIELD_PREP(field_msk, nval);
+	bits_to_set = hwm_field_prep(field_msk, nval);
 
 	hwm_locked_with_pm_intel_uncore_rmw(ddat, rgadr,
 					    bits_to_clear, bits_to_set);
-- 
2.38.0