Re: [PATCH] serial: stm32: optimize spin lock usage

kernel test robot
2021-04-12T07:25:04Z

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Hi,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on stm32/stm32-next]
[also build test WARNING on usb/usb-testing v5.12-rc7]
[cannot apply to tty/tty-testing next-20210409]
[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/dillon-minfei-gmail-com/serial-stm32-optimize-spin-lock-usage/20210412-123607
base: https://git.kernel.org/pub/scm/linux/kernel/git/atorgue/stm32.git stm32-next
config: riscv-randconfig-r034-20210412 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 9829f5e6b1bca9b61efc629770d28bb9014dec45)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install riscv cross compiling tool for clang build
# apt-get install binutils-riscv64-linux-gnu
# https://github.com/0day-ci/linux/commit/a0e81ae10c46f768437d61cd3a3dfd4d1250b375
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review dillon-minfei-gmail-com/serial-stm32-optimize-spin-lock-usage/20210412-123607
git checkout a0e81ae10c46f768437d61cd3a3dfd4d1250b375
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=riscv

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> drivers/tty/serial/stm32-usart.c:280:39: warning: variable 'flags' is uninitialized when used here [-Wuninitialized]
spin_unlock_irqrestore(&port->lock, flags);
^~~~~
drivers/tty/serial/stm32-usart.c:217:24: note: initialize the variable 'flags' to silence this warning
unsigned long c, flags;
^
= 0
1 warning generated.

vim +/flags +280 drivers/tty/serial/stm32-usart.c

211
212 static void stm32_usart_receive_chars(struct uart_port *port, bool threaded)
213 {
214 struct tty_port *tport = &port->state->port;
215 struct stm32_port *stm32_port = to_stm32_port(port);
216 const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
217 unsigned long c, flags;
218 u32 sr;
219 char flag;
220
221 if (irqd_is_wakeup_set(irq_get_irq_data(port->irq)))
222 pm_wakeup_event(tport->tty->dev, 0);
223
224 while (stm32_usart_pending_rx(port, &sr, &stm32_port->last_res,
225 threaded)) {
226 sr |= USART_SR_DUMMY_RX;
227 flag = TTY_NORMAL;
228
229 /*
230 * Status bits has to be cleared before reading the RDR:
231 * In FIFO mode, reading the RDR will pop the next data
232 * (if any) along with its status bits into the SR.
233 * Not doing so leads to misalignement between RDR and SR,
234 * and clear status bits of the next rx data.
235 *
236 * Clear errors flags for stm32f7 and stm32h7 compatible
237 * devices. On stm32f4 compatible devices, the error bit is
238 * cleared by the sequence [read SR - read DR].
239 */
240 if ((sr & USART_SR_ERR_MASK) && ofs->icr != UNDEF_REG)
241 writel_relaxed(sr & USART_SR_ERR_MASK,
242 port->membase + ofs->icr);
243
244 c = stm32_usart_get_char(port, &sr, &stm32_port->last_res);
245 port->icount.rx++;
246 if (sr & USART_SR_ERR_MASK) {
247 if (sr & USART_SR_ORE) {
248 port->icount.overrun++;
249 } else if (sr & USART_SR_PE) {
250 port->icount.parity++;
251 } else if (sr & USART_SR_FE) {
252 /* Break detection if character is null */
253 if (!c) {
254 port->icount.brk++;
255 if (uart_handle_break(port))
256 continue;
257 } else {
258 port->icount.frame++;
259 }
260 }
261
262 sr &= port->read_status_mask;
263
264 if (sr & USART_SR_PE) {
265 flag = TTY_PARITY;
266 } else if (sr & USART_SR_FE) {
267 if (!c)
268 flag = TTY_BREAK;
269 else
270 flag = TTY_FRAME;
271 }
272 }
273
274 if (uart_handle_sysrq_char(port, c))
275 continue;
276 uart_insert_char(port, sr, USART_SR_ORE, c, flag);
277 }
278
279 if (threaded)
> 280 spin_unlock_irqrestore(&port->lock, flags);
281 else
282 spin_unlock(&port->lock);
283
284 tty_flip_buffer_push(tport);
285
286 if (threaded)
287 spin_lock_irqsave(&port->lock, flags);
288 else
289 spin_lock(&port->lock);
290 }
291

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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