Hi Clark, Thank you for the patch! Perhaps something to improve: [auto build test WARNING on thierry-reding-pwm/for-next] [also build test WARNING on v5.16-rc4 next-20211208] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Clark-Wang/pwm-imx27-workaround-... base: https://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm.git for-next config: riscv-randconfig-s031-20211209 (https://download.01.org/0day-ci/archive/20211210/202112100135.Qng8J561-lk...) compiler: riscv64-linux-gcc (GCC) 11.2.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # apt-get install sparse # sparse version: v0.6.4-dirty # https://github.com/0day-ci/linux/commit/e56186a9b8501a89d138d2072cc63d107... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Clark-Wang/pwm-imx27-workaround-of-the-pwm-output-bug-when-decrease-the-duty-cycle/20211208-165523 git checkout e56186a9b8501a89d138d2072cc63d107fb303a0 # save the config file to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=riscv SHELL=/bin/bash drivers/pwm/ If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; sparse warnings: (new ones prefixed by >>) drivers/pwm/pwm-imx27.c:301:26: sparse: expected unsigned int [usertype] sar_last drivers/pwm/pwm-imx27.c:301:26: sparse: got restricted __le32 [usertype] drivers/pwm/pwm-imx27.c:302:29: sparse: expected unsigned int [usertype] sar_current drivers/pwm/pwm-imx27.c:302:29: sparse: got restricted __le32 [usertype] vim +301 drivers/pwm/pwm-imx27.c 217 218 static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, 219 const struct pwm_state *state) 220 { 221 unsigned long period_cycles, duty_cycles, prescale, counter_check, flags; 222 struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip); 223 void __iomem *reg_sar = imx->mmio_base + MX3_PWMSAR; 224 __force u32 sar_last, sar_current; 225 struct pwm_state cstate; 226 unsigned long long c; 227 unsigned long long clkrate; 228 int ret; 229 u32 cr, timeout = 1000; 230 231 pwm_get_state(pwm, &cstate); 232 233 clkrate = clk_get_rate(imx->clk_per); 234 c = clkrate * state->period; 235 236 do_div(c, NSEC_PER_SEC); 237 period_cycles = c; 238 239 prescale = period_cycles / 0x10000 + 1; 240 241 period_cycles /= prescale; 242 c = clkrate * state->duty_cycle; 243 do_div(c, NSEC_PER_SEC); 244 duty_cycles = c; 245 duty_cycles /= prescale; 246 247 /* 248 * according to imx pwm RM, the real period value should be PERIOD 249 * value in PWMPR plus 2. 250 */ 251 if (period_cycles > 2) 252 period_cycles -= 2; 253 else 254 period_cycles = 0; 255 256 /* 257 * Wait for a free FIFO slot if the PWM is already enabled, and flush 258 * the FIFO if the PWM was disabled and is about to be enabled. 259 */ 260 if (cstate.enabled) { 261 pwm_imx27_wait_fifo_slot(chip, pwm); 262 } else { 263 ret = pwm_imx27_clk_prepare_enable(imx); 264 if (ret) 265 return ret; 266 267 pwm_imx27_sw_reset(chip); 268 } 269 270 /* 271 * This is a limited workaround. When the SAR FIFO is empty, the new 272 * write value will be directly applied to SAR even the current period 273 * is not over. 274 * If the new SAR value is less than the old one, and the counter is 275 * greater than the new SAR value, the current period will not filp 276 * the level. This will result in a pulse with a duty cycle of 100%. 277 * So, writing the current value of the SAR to SAR here before updating 278 * the new SAR value can avoid this issue. 279 * 280 * Add a spin lock and turn off the interrupt to ensure that the 281 * real-time performance can be guaranteed as much as possible when 282 * operating the following operations. 283 * 284 * 1. Add a threshold of 1.5us. If the time T between the read current 285 * count value CNR and the end of the cycle is less than 1.5us, wait 286 * for T to be longer than 1.5us before updating the SAR register. 287 * This is to avoid the situation that when the first SAR is written, 288 * the current cycle just ends and the SAR FIFO that just be written 289 * is emptied again. 290 * 291 * 2. Use __raw_writel() to minimize the interval between two writes to 292 * the SAR register to increase the fastest pwm frequency supported. 293 * 294 * When the PWM period is longer than 2us(or <500KHz), this workaround 295 * can solve this problem. 296 */ 297 if (duty_cycles < imx->duty_cycle) { 298 c = clkrate * 1500; 299 do_div(c, NSEC_PER_SEC); 300 counter_check = c; 303 304 spin_lock_irqsave(&imx->lock, flags); 305 if (state->period >= 2000) { 306 while ((period_cycles - 307 readl_relaxed(imx->mmio_base + MX3_PWMCNR)) 308 < counter_check) { 309 if (!--timeout) 310 break; 311 }; 312 } 313 if (!(MX3_PWMSR_FIFOAV & 314 readl_relaxed(imx->mmio_base + MX3_PWMSR))) 315 __raw_writel(sar_last, reg_sar); 316 __raw_writel(sar_current, reg_sar); 317 spin_unlock_irqrestore(&imx->lock, flags); 318 } else 319 writel(duty_cycles, imx->mmio_base + MX3_PWMSAR); 320 321 writel(period_cycles, imx->mmio_base + MX3_PWMPR); 322 323 /* 324 * Store the duty cycle for future reference in cases where the 325 * MX3_PWMSAR register can't be read (i.e. when the PWM is disabled). 326 */ 327 imx->duty_cycle = duty_cycles; 328 329 cr = MX3_PWMCR_PRESCALER_SET(prescale) | 330 MX3_PWMCR_STOPEN | MX3_PWMCR_DOZEN | MX3_PWMCR_WAITEN | 331 FIELD_PREP(MX3_PWMCR_CLKSRC, MX3_PWMCR_CLKSRC_IPG_HIGH) | 332 MX3_PWMCR_DBGEN; 333 334 if (state->polarity == PWM_POLARITY_INVERSED) 335 cr |= FIELD_PREP(MX3_PWMCR_POUTC, 336 MX3_PWMCR_POUTC_INVERTED); 337 338 if (state->enabled) 339 cr |= MX3_PWMCR_EN; 340 341 writel(cr, imx->mmio_base + MX3_PWMCR); 342 343 if (!state->enabled) 344 pwm_imx27_clk_disable_unprepare(imx); 345 346 return 0; 347 } 348 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org