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| author | Vamshi Gajjela <vamshigajjela@google.com> | 2023-12-31 21:29:51 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-01-04 18:21:43 +0300 |
| commit | d8a02844791360ed156ce5935bc50754ea22e299 (patch) | |
| tree | 3ee39812e7b95fe01e90b75babcb0843303e4749 /drivers/tty | |
| parent | 7c45eaa813476bd195ac1227a64b52f9cf2e2030 (diff) | |
| download | linux-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.c | 12 |
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) { |