From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Jiri Slaby <jirislaby@kernel.org>,
Jay Dolan <jay.dolan@accesio.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: [PATCH v3 2/2] serial: 8250_pci: rewrite pericom_do_set_divisor()
Date: Mon, 22 Nov 2021 14:06:04 +0200 [thread overview]
Message-ID: <20211122120604.3909-3-andriy.shevchenko@linux.intel.com> (raw)
In-Reply-To: <20211122120604.3909-1-andriy.shevchenko@linux.intel.com>
From: Jay Dolan <jay.dolan@accesio.com>
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")
Signed-off-by: Jay Dolan <jay.dolan@accesio.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
drivers/tty/serial/8250/8250_pci.c | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index b793d848aeb6..60f8fffdfd77 100644
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1324,29 +1324,33 @@ pericom_do_set_divisor(struct uart_port *port, unsigned int baud,
{
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,
--
2.33.0
prev parent reply other threads:[~2021-11-22 12:06 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-22 12:06 [PATCH v3 0/2] serial: 8250_pci patches to address issues with pericom_do_set_divisor() Andy Shevchenko
2021-11-22 12:06 ` [PATCH v3 1/2] serial: 8250_pci: Fix ACCES entries in pci_serial_quirks array Andy Shevchenko
2021-11-22 12:06 ` Andy Shevchenko [this message]
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