From 56f45266df67aa0f5b2a6881c8c4d16dbfff6b7d Mon Sep 17 00:00:00 2001 From: Ken Sloat Date: Thu, 15 Dec 2022 16:07:15 +0000 Subject: [PATCH] pwm: xilinx: Fix u32 overflow issue in 32-bit width PWM mode. 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 Reviewed-by: Michal Simek Reviewed-by: Sean Anderson Link: https://lore.kernel.org/r/SJ0P222MB0107490C5371B848EF04351CA1E19@SJ0P222MB0107.NAMP222.PROD.OUTLOOK.COM Signed-off-by: Michal Simek --- 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 c0f56fe6d22aed..d116f18de899c3 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; }; /**