[M] Change in coreboot[main]: drivers/pc80/pc/spkmodem.c: Use beep() instead of own implementation

[Nicholas Chin (Code Review)]

Nicholas Chin has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/83372?usp=email )

Change subject: drivers/pc80/pc/spkmodem.c: Use beep() instead of own implementation
......................................................................

drivers/pc80/pc/spkmodem.c: Use beep() instead of own implementation

Commit 23b79483554f (pc80/i8254: Add speaker beep function) added a
driver to play beeps using the 8254 PIT chip and the PC speaker, which
is essentially the same as the make_tone() function in spkmodem.c. Drop
the duplicate functionality provided by make_tone() in favour of the
common beep() function, which also has a more intuitive signature.

Converting the make_tone() arguments to beep() arguments is not trivial,
as they are different in meaning and requires some background knowledge
of PIT programming, explained briefly here.

The `duration` argument to make_tone() is somewhat misleading, as it is
not used as a direct number of units of time, but rather the number of
PIT counter reloads to wait for. The frequency of the reloads is related
to the `freq_count` argument, which is the value the counter is reloaded
to when it counts down to 0. Since the counter decrements at 1193181 Hz,
dividing this frequency by the desired frequency of the tone gives the
counter reload value, which was used to calculate the freq_count
argument for the calls to make_tone().

However, since the PIT output toggles at every reload, each full cycle
occurs at half the desired frequency. To compensate for this, mode 3
(square wave generator) of the PIT chip actually decrements the counter
by 2 each time so that the counter reloads twice as often. Thus, each
reload occurs every 1 / (frequency * 2) seconds.

Since `duration` counts reloads, multiplying it by the time between
reloads gives the time in seconds, and thus the following formula was
used to convert `duration` into a millisecond value to pass as the
duration_msec argument for beep():
    duration_msec = 1000 * duration/(2*frequency)

Change-Id: If95b518c991a0d700489566e5609344ca2cbbc7a
Signed-off-by: Nicholas Chin 
---
M src/drivers/pc80/pc/spkmodem.c
1 file changed, 5 insertions(+), 81 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/72/83372/1

diff --git a/src/drivers/pc80/pc/spkmodem.c b/src/drivers/pc80/pc/spkmodem.c
index 9e457f7..5ef0dd1 100644
--- a/src/drivers/pc80/pc/spkmodem.c
+++ b/src/drivers/pc80/pc/spkmodem.c
@@ -2,95 +2,19 @@

#include <arch/io.h>
 #include <console/spkmodem.h>
-
-#define SPEAKER_PIT_FREQUENCY		0x1234dd
-
-enum {
-	PIT_COUNTER_0 = 0x40,
-	PIT_COUNTER_1 = 0x41,
-	PIT_COUNTER_2 = 0x42,
-	PIT_CTRL = 0x43,
-	PIT_SPEAKER_PORT = 0x61,
-};
-
-enum {
-	PIT_SPK_TMR2 = 0x01,
-	PIT_SPK_DATA = 0x02,
-	PIT_SPK_TMR2_LATCH = 0x20
-};
-
-enum {
-	PIT_CTRL_SELECT_MASK = 0xc0,
-	PIT_CTRL_SELECT_0 = 0x00,
-	PIT_CTRL_SELECT_1 = 0x40,
-	PIT_CTRL_SELECT_2 = 0x80,
-
-	PIT_CTRL_READLOAD_MASK = 0x30,
-	PIT_CTRL_COUNTER_LATCH = 0x00,
-	PIT_CTRL_READLOAD_LSB = 0x10,
-	PIT_CTRL_READLOAD_MSB = 0x20,
-	PIT_CTRL_READLOAD_WORD = 0x30,
-
-	PIT_CTRL_MODE_MASK = 0x0e,
-	PIT_CTRL_INTR_ON_TERM = 0x00,
-	PIT_CTRL_PROGR_ONE_SHOT = 0x02,
-
-	PIT_CTRL_RATE_GEN = 0x04,
-
-	PIT_CTRL_SQUAREWAVE_GEN = 0x06,
-	PIT_CTRL_SOFTSTROBE = 0x08,
-
-	PIT_CTRL_HARDSTROBE = 0x0a,
-
-	PIT_CTRL_COUNT_MASK = 0x01,
-	PIT_CTRL_COUNT_BINARY = 0x00,
-	PIT_CTRL_COUNT_BCD = 0x01
-};
-
-static void
-make_tone(uint16_t freq_count, unsigned int duration)
-{
-	outb(PIT_CTRL_SELECT_2
-		   | PIT_CTRL_READLOAD_WORD
-		   | PIT_CTRL_SQUAREWAVE_GEN
-		   | PIT_CTRL_COUNT_BINARY, PIT_CTRL);
-
-	outb(freq_count & 0xff, PIT_COUNTER_2);
-
-	outb((freq_count >> 8) & 0xff, PIT_COUNTER_2);
-
-	outb(inb(PIT_SPEAKER_PORT)
-		   | PIT_SPK_TMR2 | PIT_SPK_DATA,
-		   PIT_SPEAKER_PORT);
-
-	for (; duration; duration--) {
-		unsigned short counter, previous_counter = 0xffff;
-
-		while (1) {
-			counter = inb(PIT_COUNTER_2);
-			counter |= ((uint16_t)inb(PIT_COUNTER_2)) << 8;
-			if (counter > previous_counter) {
-				previous_counter = counter;
-				break;
-			}
-			previous_counter = counter;
-		}
-	}
-}
+#include <pc80/i8254.h>

void spkmodem_tx_byte(unsigned char c)
 {
    int i;
-
-	make_tone(SPEAKER_PIT_FREQUENCY / 200, 4);
+	beep(200, 10);
    for (i = 7; i >= 0; i--) {
    	if ((c >> i) & 1)
-			make_tone(SPEAKER_PIT_FREQUENCY / 2000, 20);
+			beep(2000, 5);
    	else
-			make_tone(SPEAKER_PIT_FREQUENCY / 4000, 40);
-		make_tone(SPEAKER_PIT_FREQUENCY / 1000, 10);
+			beep(4000, 5);
+		beep(1000, 5);
    }
-	make_tone(SPEAKER_PIT_FREQUENCY / 200, 0);
 }

void spkmodem_init(void)