From: Ken Sloat ksloat@designlinxhs.com
[ Upstream commit 56f45266df67aa0f5b2a6881c8c4d16dbfff6b7d ]
This timer HW supports 8, 16 and 32-bit timer widths. This driver currently uses a u32 to store the max possible value of the timer. However, statements perform addition of 2 in xilinx_pwm_apply() when calculating the period_cycles and duty_cycles values. Since priv->max is a u32, this will result in an overflow to 1 which will not only be incorrect but fail on range comparison. This results in making it impossible to set the PWM in this timer mode.
There are two obvious solutions to the current problem: 1. Cast each instance where overflow occurs to u64. 2. Change priv->max from a u32 to a u64.
Solution #1 requires more code modifications, and leaves opportunity to introduce similar overflows if other math statements are added in the future. These may also go undetected if running in non 32-bit timer modes.
Solution #2 is the much smaller and cleaner approach and thus the chosen method in this patch.
This was tested on a Zynq UltraScale+ with multiple instances of the PWM IP.
Signed-off-by: Ken Sloat ksloat@designlinxhs.com Reviewed-by: Michal Simek michal.simek@amd.com Reviewed-by: Sean Anderson sean.anderson@seco.com Link: https://lore.kernel.org/r/SJ0P222MB0107490C5371B848EF04351CA1E19@SJ0P222MB01... Signed-off-by: Michal Simek michal.simek@amd.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/clocksource/timer-xilinx.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/clocksource/timer-xilinx.h b/include/clocksource/timer-xilinx.h index c0f56fe6d22ae..d116f18de899c 100644 --- a/include/clocksource/timer-xilinx.h +++ b/include/clocksource/timer-xilinx.h @@ -41,7 +41,7 @@ struct regmap; struct xilinx_timer_priv { struct regmap *map; struct clk *clk; - u32 max; + u64 max; };
/**