From d8a02844791360ed156ce5935bc50754ea22e299 Mon Sep 17 00:00:00 2001 From: Vamshi Gajjela Date: Sun, 31 Dec 2023 23:59:51 +0530 Subject: serial: 8250_dw: Do not bailout on UCV read returning zero Designware UART has optional feature FIFO_MODE to implement FIFO. Encoding FIFO capabilities through Component Parameter Register CPR is optional and it can be enabled using parameter UART_ADD_ENCODED_PARAMS. Driver can exercise fifo capabilities by decoding CPR if implemented or from cpr_val provided from the dw8250_platform_data otherwise. dw8250_setup_port() checks for CPR or cpr_val to determine FIFO size only when Component Version (UCV) is non-zero. Bailing out early on UCV read returning zero will leave fifosize as zero and !UART_CAP_FIFO, hence prevent early return and continue to process CPR or cpr_val for the driver to utilize FIFO. Non-zero UCV implies ADDITIONAL_FEATURES=1, preventing early return will not be an overhead here. Signed-off-by: Vamshi Gajjela Link: https://lore.kernel.org/r/20231231182951.877805-1-vamshigajjela@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_dwlib.c | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-) (limited to 'drivers/tty/serial') diff --git a/drivers/tty/serial/8250/8250_dwlib.c b/drivers/tty/serial/8250/8250_dwlib.c index 136ad093c5b6..3e33ddf7bc80 100644 --- a/drivers/tty/serial/8250/8250_dwlib.c +++ b/drivers/tty/serial/8250/8250_dwlib.c @@ -271,16 +271,10 @@ void dw8250_setup_port(struct uart_port *p) p->set_divisor = dw8250_set_divisor; } - /* - * If the Component Version Register returns zero, we know that - * ADDITIONAL_FEATURES are not enabled. No need to go any further. - */ reg = dw8250_readl_ext(p, DW_UART_UCV); - if (!reg) - return; - - dev_dbg(p->dev, "Designware UART version %c.%c%c\n", - (reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff); + if (reg) + dev_dbg(p->dev, "Designware UART version %c.%c%c\n", + (reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff); reg = dw8250_readl_ext(p, DW_UART_CPR); if (!reg) { -- cgit v1.2.3