From: Jay Dolan <jay.dolan@xxxxxxxxxxx>
commit bb1201d4b38ec67bd9a871cf86b0cc10f28b15b5 upstream.
Have pericom_do_set_divisor() use the uartclk instead of a hard coded
value to work with different speed crystals. Tested with 14.7456 and 24
MHz crystals.
Have pericom_do_set_divisor() always calculate the divisor rather than
call serial8250_do_set_divisor() for rates below baud_base.
Do not write registers or call serial8250_do_set_divisor() if valid
divisors could not be found.
Fixes: 6bf4e42f1d19 ("serial: 8250: Add support for higher baud rates to Pericom chips")
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jay Dolan <jay.dolan@xxxxxxxxxxx>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20211122120604.3909-3-andriy.shevchenko@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_pci.c | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1349,29 +1349,33 @@ pericom_do_set_divisor(struct uart_port
{
int scr;
int lcr;
- int actual_baud;
- int tolerance;
- for (scr = 5 ; scr <= 15 ; scr++) {
- actual_baud = 921600 * 16 / scr;
- tolerance = actual_baud / 50;
+ for (scr = 16; scr > 4; scr--) {
+ unsigned int maxrate = port->uartclk / scr;
+ unsigned int divisor = max(maxrate / baud, 1U);
+ int delta = maxrate / divisor - baud;
- if ((baud < actual_baud + tolerance) &&
- (baud > actual_baud - tolerance)) {
+ if (baud > maxrate + baud / 50)
+ continue;
+ if (delta > baud / 50)
+ divisor++;
+
+ if (divisor > 0xffff)
+ continue;
+
+ /* Update delta due to possible divisor change */
+ delta = maxrate / divisor - baud;
+ if (abs(delta) < baud / 50) {
lcr = serial_port_in(port, UART_LCR);
serial_port_out(port, UART_LCR, lcr | 0x80);
-
- serial_port_out(port, UART_DLL, 1);
- serial_port_out(port, UART_DLM, 0);
+ serial_port_out(port, UART_DLL, divisor & 0xff);
+ serial_port_out(port, UART_DLM, divisor >> 8 & 0xff);
serial_port_out(port, 2, 16 - scr);
serial_port_out(port, UART_LCR, lcr);
return;
- } else if (baud > actual_baud) {
- break;
}
}
- serial8250_do_set_divisor(port, baud, quot, quot_frac);
}
static int pci_pericom_setup(struct serial_private *priv,
const struct pciserial_board *board,
