[v2] drm:sprd: Correct left shift operator evaluating constant expression

Commit Message

Karan Sanghavi Nov. 8, 2024, 5:11 p.m. UTC

The left shift operation followed by a mask with 0xf will
always result in 0. To correctly evaluate the expression for
the bitwise OR operation, use a right shift instead.

Reported by Coverity Scan CID: 1511468

Fixes: 1c66496b1391 ("drm/sprd: add Unisoc's drm mipi dsi&dphy driver")

Reviewed-by: Chunyan Zhang <[e-mail]>
Signed-off-by: Karan Sanghavi <[e-mail]>
---
Coverity Scan Message:
CID 1511468: (#1 of 1): Wrong operator used (CONSTANT_EXPRESSION_RESULT)
operator_confusion: (pll->kint << 4) & 15 is always 0 regardless of the 
values of its operands. This occurs as the bitwise second operand of "|"
---
Changes in v2:
- Added the fixes tag
- Link to v1: https://lore.kernel.org/r/[e-mail]
---
 drivers/gpu/drm/sprd/megacores_pll.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


---
base-commit: 81983758430957d9a5cb3333fe324fd70cf63e7e
change-id: 20241105-coverity1511468wrongoperator-20130bcd4240

Best regards,

Patch

diff --git a/drivers/gpu/drm/sprd/megacores_pll.c b/drivers/gpu/drm/sprd/megacores_pll.c
index 3091dfdc11e3..43c10a5fc441 100644
--- a/drivers/gpu/drm/sprd/megacores_pll.c
+++ b/drivers/gpu/drm/sprd/megacores_pll.c
@@ -94,7 +94,7 @@  static void dphy_set_pll_reg(struct dphy_pll *pll, struct regmap *regmap)
 	reg_val[3] = pll->vco_band | (pll->sdm_en << 1) | (pll->refin << 2);
 	reg_val[4] = pll->kint >> 12;
 	reg_val[5] = pll->kint >> 4;
-	reg_val[6] = pll->out_sel | ((pll->kint << 4) & 0xf);
+	reg_val[6] = pll->out_sel | ((pll->kint >> 4) & 0xf);
 	reg_val[7] = 1 << 4;
 	reg_val[8] = pll->det_delay;