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 <l...@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-...@lists.01.org

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