[PATCH 3/5] clk: sunxi-ng: mp: support clocks with just a shift register

[Andre Przywara <andre.przywara@arm.com>]

The "mp" clock models a mod clock with divider and a shift field. At
least one clock in the Allwinner A523 features just a power-of-2 divider
field, so support an initialisation of the clock without providing an
actual divider field.

Add a check whether the "width" field is 0, and skip the divider
handling in this case, as the GENMASK macro will not work with a zero
length.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 drivers/clk/sunxi-ng/ccu_mp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/sunxi-ng/ccu_mp.c b/drivers/clk/sunxi-ng/ccu_mp.c
index 354c981943b6f..a03dac294d048 100644
--- a/drivers/clk/sunxi-ng/ccu_mp.c
+++ b/drivers/clk/sunxi-ng/ccu_mp.c
@@ -236,9 +236,11 @@ static int ccu_mp_set_rate(struct clk_hw *hw, unsigned long rate,
 	spin_lock_irqsave(cmp->common.lock, flags);
 
 	reg = readl(cmp->common.base + cmp->common.reg);
-	reg &= ~GENMASK(cmp->m.width + cmp->m.shift - 1, cmp->m.shift);
+	if (cmp->m.width)
+		reg &= ~GENMASK(cmp->m.width + cmp->m.shift - 1, cmp->m.shift);
 	reg &= ~GENMASK(cmp->p.width + cmp->p.shift - 1, cmp->p.shift);
-	reg |= (m - cmp->m.offset) << cmp->m.shift;
+	if (cmp->m.width)
+		reg |= (m - cmp->m.offset) << cmp->m.shift;
 	if (shift)
 		reg |= ilog2(p) << cmp->p.shift;
 	else
-- 
2.46.3