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-rw-r--r--src/device/software_i2c.c54
1 files changed, 29 insertions, 25 deletions
diff --git a/src/device/software_i2c.c b/src/device/software_i2c.c
index ec6722bbed..402f1d4131 100644
--- a/src/device/software_i2c.c
+++ b/src/device/software_i2c.c
@@ -29,6 +29,11 @@
#define spew(...) do { if (SPEW) printk(BIOS_SPEW, ##__VA_ARGS__); } while (0)
+#define ERR_NACK -2
+#define ERR_TIMEOUT -3
+#define ERR_ARB -4
+#define ERR_WEDGE -5
+
struct software_i2c_ops *software_i2c[SOFTWARE_I2C_MAX_BUS];
/*
@@ -71,7 +76,7 @@ static int wait_for_scl(unsigned bus, const char *error_context)
if (!__wait(bus, TIMEOUT_US, 1)) {
printk(BIOS_ERR, "software_i2c(%d): ERROR: Clock stretching "
"timeout %s!\n", bus, error_context);
- return -1;
+ return ERR_TIMEOUT;
}
return 0;
@@ -88,13 +93,13 @@ static int start_cond(unsigned bus)
/* Might need to wait for clock stretching if repeated start. */
software_i2c[bus]->set_scl(bus, 1);
if (wait_for_scl(bus, "before start condition"))
- return -1;
+ return ERR_TIMEOUT;
wait(bus); /* Repeated start setup time, minimum 4.7us */
if (!software_i2c[bus]->get_sda(bus)) {
printk(BIOS_ERR, "software_i2c(%d): Arbitration lost trying "
"to send start condition!\n", bus);
- return -1;
+ return ERR_ARB;
}
/* SCL is high, transition SDA low as first part of start condition. */
@@ -121,7 +126,7 @@ static int stop_cond(unsigned bus)
assert(!software_i2c[bus]->get_scl(bus));
software_i2c[bus]->set_scl(bus, 1);
if (wait_for_scl(bus, "before stop condition"))
- return -1;
+ return ERR_TIMEOUT;
wait(bus); /* Stop bit setup time, minimum 4us */
/* SCL is high, transition SDA high to signal stop condition. */
@@ -148,20 +153,20 @@ static int out_bit(unsigned bus, int bit)
if (bit && !software_i2c[bus]->get_sda(bus)) {
printk(BIOS_ERR, "software_i2c(%d): ERROR: SDA wedged low "
"by slave before clock pulse on transmit!\n", bus);
- return -1;
+ return ERR_WEDGE;
}
/* Clock stretching */
assert(!software_i2c[bus]->get_scl(bus));
software_i2c[bus]->set_scl(bus, 1);
if (wait_for_scl(bus, "on transmit"))
- return -1;
+ return ERR_TIMEOUT;
wait(bus);
if (bit && !software_i2c[bus]->get_sda(bus)) {
printk(BIOS_ERR, "software_i2c(%d): ERROR: SDA wedged low "
"by slave after clock pulse on transmit!\n", bus);
- return -1;
+ return ERR_WEDGE;
}
assert(software_i2c[bus]->get_scl(bus));
@@ -185,7 +190,7 @@ static int in_bit(unsigned bus)
assert(!software_i2c[bus]->get_scl(bus));
software_i2c[bus]->set_scl(bus, 1);
if (wait_for_scl(bus, "on receive"))
- return -1;
+ return ERR_TIMEOUT;
/* SCL is high, now data is valid */
bit = software_i2c[bus]->get_sda(bus);
@@ -202,11 +207,11 @@ static int in_bit(unsigned bus)
static int out_byte(unsigned bus, u8 byte)
{
unsigned bit;
- int nack;
+ int nack, ret;
for (bit = 0; bit < 8; bit++)
- if (out_bit(bus, (byte >> (7 - bit)) & 0x1) < 0)
- return -1;
+ if ((ret = out_bit(bus, (byte >> (7 - bit)) & 0x1)) < 0)
+ return ret;
nack = in_bit(bus);
@@ -214,22 +219,22 @@ static int out_byte(unsigned bus, u8 byte)
printk(BIOS_DEBUG, "software_i2c(%d): wrote byte 0x%02x, "
"received %s\n", bus, byte, nack ? "NAK" : "ACK");
- return nack;
+ return nack > 0 ? ERR_NACK : nack;
}
static int in_byte(unsigned bus, int ack)
{
u8 byte = 0;
- int i;
+ int i, ret;
for (i = 0; i < 8; ++i) {
int bit = in_bit(bus);
if (bit < 0)
- return -1;
+ return bit;
byte = (byte << 1) | bit;
}
- if (out_bit(bus, !ack) < 0)
- return -1;
+ if ((ret = out_bit(bus, !ack)) < 0)
+ return ret;
if (DEBUG)
printk(BIOS_DEBUG, "software_i2c(%d): read byte 0x%02x, "
@@ -240,17 +245,16 @@ static int in_byte(unsigned bus, int ack)
int software_i2c_transfer(unsigned bus, struct i2c_msg *segments, int count)
{
- int i;
+ int i, ret;
struct i2c_msg *seg;
for (seg = segments; seg - segments < count; seg++) {
- if (start_cond(bus) < 0)
- return -1;
+ if ((ret = start_cond(bus)) < 0)
+ return ret;
const u8 addr_dir = seg->slave << 1 | !!(seg->flags & I2C_M_RD);
- if (out_byte(bus, addr_dir) < 0)
- return -1;
+ if ((ret = out_byte(bus, addr_dir)) < 0)
+ return ret;
for (i = 0; i < seg->len; i++) {
- int ret;
if (seg->flags & I2C_M_RD) {
ret = in_byte(bus, i < seg->len - 1);
seg->buf[i] = (u8)ret;
@@ -258,11 +262,11 @@ int software_i2c_transfer(unsigned bus, struct i2c_msg *segments, int count)
ret = out_byte(bus, seg->buf[i]);
}
if (ret < 0)
- return -1;
+ return ret;
}
}
- if (stop_cond(bus) < 0)
- return -1;
+ if ((ret = stop_cond(bus)) < 0)
+ return ret;
return 0;
}