Re: [PATCH v1 tty-next 4/4] 8250: microchip: pci1xxxx: Add Burst mode transmission support in uart driver for reading from FIFO
From: Dan Carpenter
Date: Tue Jan 02 2024 - 09:07:01 EST
Hi Rengarajan,
kernel test robot noticed the following build warnings:
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Rengarajan-S/8250-microchip-pci1xxxx-Rearranging-the-structure-declarations/20231215-234606
base: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git tty-testing
patch link: https://lore.kernel.org/r/20231215151123.41812-5-rengarajan.s%40microchip.com
patch subject: [PATCH v1 tty-next 4/4] 8250: microchip: pci1xxxx: Add Burst mode transmission support in uart driver for reading from FIFO
config: i386-randconfig-141-20231216 (https://download.01.org/0day-ci/archive/20231216/202312161205.f6EpLZln-lkp@xxxxxxxxx/config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
| Closes: https://lore.kernel.org/r/202312161205.f6EpLZln-lkp@xxxxxxxxx/
smatch warnings:
drivers/tty/serial/8250/8250_pci1xxxx.c:395 pci1xxxx_process_write_data() warn: should this be 'valid_burst_count == -1'
vim +395 drivers/tty/serial/8250/8250_pci1xxxx.c
eeaa9176002041 Rengarajan S 2023-12-15 351 static void pci1xxxx_process_write_data(struct uart_port *port,
eeaa9176002041 Rengarajan S 2023-12-15 352 struct circ_buf *xmit,
eeaa9176002041 Rengarajan S 2023-12-15 353 int *data_empty_count,
eeaa9176002041 Rengarajan S 2023-12-15 354 u32 *valid_byte_count)
eeaa9176002041 Rengarajan S 2023-12-15 355 {
eeaa9176002041 Rengarajan S 2023-12-15 356 u32 valid_burst_count = *valid_byte_count / UART_BURST_SIZE;
eeaa9176002041 Rengarajan S 2023-12-15 357
eeaa9176002041 Rengarajan S 2023-12-15 358 /*
eeaa9176002041 Rengarajan S 2023-12-15 359 * Each transaction transfers data in DWORDs. If there are less than
eeaa9176002041 Rengarajan S 2023-12-15 360 * four remaining valid_byte_count to transfer or if the circular
eeaa9176002041 Rengarajan S 2023-12-15 361 * buffer has insufficient space for a DWORD, the data is transferred
eeaa9176002041 Rengarajan S 2023-12-15 362 * one byte at a time.
eeaa9176002041 Rengarajan S 2023-12-15 363 */
eeaa9176002041 Rengarajan S 2023-12-15 364 while (valid_burst_count--) {
This loop ends with valid_burst_count set to -1. (Post operation).
eeaa9176002041 Rengarajan S 2023-12-15 365 if (*data_empty_count - UART_BURST_SIZE < 0)
eeaa9176002041 Rengarajan S 2023-12-15 366 break;
eeaa9176002041 Rengarajan S 2023-12-15 367 if (xmit->tail > (UART_XMIT_SIZE - UART_BURST_SIZE))
eeaa9176002041 Rengarajan S 2023-12-15 368 break;
eeaa9176002041 Rengarajan S 2023-12-15 369 writel(*(unsigned int *)&xmit->buf[xmit->tail],
eeaa9176002041 Rengarajan S 2023-12-15 370 port->membase + UART_TX_BURST_FIFO);
eeaa9176002041 Rengarajan S 2023-12-15 371 *valid_byte_count -= UART_BURST_SIZE;
eeaa9176002041 Rengarajan S 2023-12-15 372 *data_empty_count -= UART_BURST_SIZE;
eeaa9176002041 Rengarajan S 2023-12-15 373 xmit->tail = (xmit->tail + UART_BURST_SIZE) &
eeaa9176002041 Rengarajan S 2023-12-15 374 (UART_XMIT_SIZE - 1);
eeaa9176002041 Rengarajan S 2023-12-15 375 }
eeaa9176002041 Rengarajan S 2023-12-15 376
eeaa9176002041 Rengarajan S 2023-12-15 377 while (*valid_byte_count--) {
eeaa9176002041 Rengarajan S 2023-12-15 378 if (*data_empty_count - UART_BYTE_SIZE < 0)
eeaa9176002041 Rengarajan S 2023-12-15 379 break;
eeaa9176002041 Rengarajan S 2023-12-15 380 writeb(xmit->buf[xmit->tail], port->membase +
eeaa9176002041 Rengarajan S 2023-12-15 381 UART_TX_BYTE_FIFO);
eeaa9176002041 Rengarajan S 2023-12-15 382 *data_empty_count -= UART_BYTE_SIZE;
eeaa9176002041 Rengarajan S 2023-12-15 383
eeaa9176002041 Rengarajan S 2023-12-15 384 /*
eeaa9176002041 Rengarajan S 2023-12-15 385 * When the tail of the circular buffer is reached, the next
eeaa9176002041 Rengarajan S 2023-12-15 386 * byte is transferred to the beginning of the buffer.
eeaa9176002041 Rengarajan S 2023-12-15 387 */
eeaa9176002041 Rengarajan S 2023-12-15 388 xmit->tail = (xmit->tail + UART_BYTE_SIZE) &
eeaa9176002041 Rengarajan S 2023-12-15 389 (UART_XMIT_SIZE - 1);
eeaa9176002041 Rengarajan S 2023-12-15 390
eeaa9176002041 Rengarajan S 2023-12-15 391 /*
eeaa9176002041 Rengarajan S 2023-12-15 392 * If there are any pending burst count, data is handled by
eeaa9176002041 Rengarajan S 2023-12-15 393 * transmitting DWORDs at a time.
eeaa9176002041 Rengarajan S 2023-12-15 394 */
eeaa9176002041 Rengarajan S 2023-12-15 @395 if (valid_burst_count && (xmit->tail <
^^^^^^^^^^^^^^^^^
So this test should be if valid_burst_count != -1. Or if
valid_burst_count != UINT_MAX because it's unsigned...
eeaa9176002041 Rengarajan S 2023-12-15 396 (UART_XMIT_SIZE - UART_BURST_SIZE)))
eeaa9176002041 Rengarajan S 2023-12-15 397 break;
eeaa9176002041 Rengarajan S 2023-12-15 398 }
eeaa9176002041 Rengarajan S 2023-12-15 399 }
--
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