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authorVamshi Gajjela <vamshigajjela@google.com>2023-12-31 21:29:51 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2024-01-04 18:21:43 +0300
commitd8a02844791360ed156ce5935bc50754ea22e299 (patch)
tree3ee39812e7b95fe01e90b75babcb0843303e4749 /drivers/tty
parent7c45eaa813476bd195ac1227a64b52f9cf2e2030 (diff)
downloadlinux-d8a02844791360ed156ce5935bc50754ea22e299.tar.xz
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 <vamshigajjela@google.com> Link: https://lore.kernel.org/r/20231231182951.877805-1-vamshigajjela@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/serial/8250/8250_dwlib.c12
1 files changed, 3 insertions, 9 deletions
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) {