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Diffstat (limited to 'meta/recipes-kernel/linux/linux-rp-2.6.24/serial-add-support-for-non-standard-xtals-to-16c950-driver.patch')
-rw-r--r--meta/recipes-kernel/linux/linux-rp-2.6.24/serial-add-support-for-non-standard-xtals-to-16c950-driver.patch155
1 files changed, 155 insertions, 0 deletions
diff --git a/meta/recipes-kernel/linux/linux-rp-2.6.24/serial-add-support-for-non-standard-xtals-to-16c950-driver.patch b/meta/recipes-kernel/linux/linux-rp-2.6.24/serial-add-support-for-non-standard-xtals-to-16c950-driver.patch
new file mode 100644
index 0000000000..b513ba1466
--- /dev/null
+++ b/meta/recipes-kernel/linux/linux-rp-2.6.24/serial-add-support-for-non-standard-xtals-to-16c950-driver.patch
@@ -0,0 +1,155 @@
1
2From: Petr Vandrovec <vandrove@vc.cvut.cz>
3
4Patch below adds support for using different prescaler than 16 for 16c950
5chips. This is needed for using Fujitsu-Siemens Connect2Air compact-flash
6card, which comes (apparently) with 806kHz clocks, and so you have to
7program prescaler for division by 7, and DLAB to 1, to get 115200Bd.
8
9To get card properly running you also have to add lines below to
10/etc/pcmcia/serial.opts so kernel knows that base speed is not 115200 but
1150400 (50400 * 16 = 806400; 806400 / 7 = 115200). As I've found no code
12specifying baud_rate in serial_cs, I assume that specifying it in
13serial.opts is right way to do this type of things.
14
15Patch also fixes problem that for UPF_MAGIC_MULTIPLIER maximum possible
16baud rate passed to uart code was uartclk / 16 while correct value for
17these devices (and for 16c950) is uartclk / 4.
18
19Patch also fixes problem that for UPF_MAGIC_MULTIPLIER devices with
20baud_rate 19200 or 9600 spd_cust did not work correctly. Not that such
21devices exist, but we should not ignore spd_cust, user probably knows why
22he asked for spd_cust.
23
24serial.opts:
25
26case "$MANFID-$FUNCID-$PRODID_1-$PRODID_2-$PRODID_3-$PRODID_4" in
27'0279,950b-2-GPRS Modem---')
28 SERIAL_OPTS="baud_base 50400"
29 ;;
30esac
31
32Cc: David Woodhouse <dwmw2@infradead.org>
33Signed-off-by: Andrew Morton <akpm@osdl.org>
34---
35
36 drivers/serial/8250.c | 82 +++++++++++++++++++++++++++++++++++++++-----------
37 1 file changed, 64 insertions(+), 18 deletions(-)
38
39Index: linux-2.6.21/drivers/serial/8250.c
40===================================================================
41--- linux-2.6.21.orig/drivers/serial/8250.c 2007-07-01 16:59:52.000000000 +0100
42+++ linux-2.6.21/drivers/serial/8250.c 2007-07-01 17:01:21.000000000 +0100
43@@ -1964,24 +1964,58 @@ static void serial8250_shutdown(struct u
44 serial_unlink_irq_chain(up);
45 }
46
47-static unsigned int serial8250_get_divisor(struct uart_port *port, unsigned int baud)
48+static unsigned int serial8250_get_divisor(struct uart_port *port, unsigned int baud,
49+ unsigned int *prescaler)
50 {
51- unsigned int quot;
52-
53- /*
54- * Handle magic divisors for baud rates above baud_base on
55- * SMSC SuperIO chips.
56+ /*
57+ * Use special handling only if user did not supply its own divider.
58+ * spd_cust is defined in terms of baud_base, so always use default
59+ * prescaler when spd_cust is requested.
60 */
61- if ((port->flags & UPF_MAGIC_MULTIPLIER) &&
62- baud == (port->uartclk/4))
63- quot = 0x8001;
64- else if ((port->flags & UPF_MAGIC_MULTIPLIER) &&
65- baud == (port->uartclk/8))
66- quot = 0x8002;
67- else
68- quot = uart_get_divisor(port, baud);
69
70- return quot;
71+ *prescaler = 16;
72+ if (baud != 38400 || (port->flags & UPF_SPD_MASK) != UPF_SPD_CUST) {
73+ unsigned int quot = port->uartclk / baud;
74+
75+ /*
76+ * Handle magic divisors for baud rates above baud_base on
77+ * SMSC SuperIO chips.
78+ */
79+ if (port->flags & UPF_MAGIC_MULTIPLIER) {
80+ if (quot == 4) {
81+ return 0x8001;
82+ } else if (quot == 8) {
83+ return 0x8002;
84+ }
85+ }
86+ if (port->type == PORT_16C950) {
87+ /*
88+ * This computes TCR value (4 to 16), not CPR value (which can
89+ * be between 1.000 and 31.875) - chip I have uses XTAL of
90+ * 806400Hz, and so a division by 7 is required to get 115200Bd.
91+ * I'm leaving CPR disabled for now, until someone will
92+ * hit even more exotic XTAL (it is needed to get 500kbps
93+ * or 1000kbps from 18.432MHz XTAL, but I have no device
94+ * which would benefit from doing that).
95+ *
96+ * If we can use divide by 16, use it. Otherwise look for
97+ * better prescaler, from 15 to 4. If quotient cannot
98+ * be divided by any integer value between 4 and 15, use 4.
99+ */
100+ if (quot & 0x0F) {
101+ unsigned int div;
102+
103+ for (div = 15; div > 4; div--) {
104+ if (quot % div == 0) {
105+ break;
106+ }
107+ }
108+ *prescaler = div;
109+ return quot / div;
110+ }
111+ }
112+ }
113+ return uart_get_divisor(port, baud);
114 }
115
116 static void
117@@ -1991,7 +2025,7 @@ serial8250_set_termios(struct uart_port
118 struct uart_8250_port *up = (struct uart_8250_port *)port;
119 unsigned char cval, fcr = 0;
120 unsigned long flags;
121- unsigned int baud, quot;
122+ unsigned int baud, quot, prescaler;
123
124 switch (termios->c_cflag & CSIZE) {
125 case CS5:
126@@ -2023,8 +2057,13 @@ serial8250_set_termios(struct uart_port
127 /*
128 * Ask the core to calculate the divisor for us.
129 */
130- baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
131- quot = serial8250_get_divisor(port, baud);
132+ if (port->type == PORT_16C950 || (port->flags & UPF_MAGIC_MULTIPLIER)) {
133+ baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/4);
134+ } else {
135+ baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
136+ }
137+ quot = serial8250_get_divisor(port, baud, &prescaler);
138+
139
140 /*
141 * Oxford Semi 952 rev B workaround
142@@ -2139,6 +2178,13 @@ serial8250_set_termios(struct uart_port
143 serial_dl_write(up, quot);
144
145 /*
146+ * Program prescaler for 16C950 chips.
147+ */
148+ if (up->port.type == PORT_16C950) {
149+ serial_icr_write(up, UART_TCR, prescaler == 16 ? 0 : prescaler);
150+ }
151+
152+ /*
153 * LCR DLAB must be set to enable 64-byte FIFO mode. If the FCR
154 * is written without DLAB set, this mode will be disabled.
155 */
generated by cgit v1.2.3-54-g00ecf (git 2.39.0) at 2024-04-27 11:00:19 +0000