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i2c: bcm2835: Add debug support
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This adds a debug module parameter to aid in debugging transfer issues
by printing info to the kernel log. When enabled, status values are
collected in the interrupt routine and msg info in
bcm2835_i2c_start_transfer(). This is done in a way that tries to avoid
affecting timing. Having printk in the isr can mask issues.

debug values (additive):
1: Print info on error
2: Print info on all transfers
3: Print messages before transfer is started

The value can be changed at runtime:
/sys/module/i2c_bcm2835/parameters/debug

Example output, debug=3:
[  747.114448] bcm2835_i2c_xfer: msg(1/2) write addr=0x54, len=2 flags= [i2c1]
[  747.114463] bcm2835_i2c_xfer: msg(2/2) read addr=0x54, len=32 flags= [i2c1]
[  747.117809] start_transfer: msg(1/2) write addr=0x54, len=2 flags= [i2c1]
[  747.117825] isr: remain=2, status=0x30000055 : TA TXW TXD TXE  [i2c1]
[  747.117839] start_transfer: msg(2/2) read addr=0x54, len=32 flags= [i2c1]
[  747.117849] isr: remain=32, status=0xd0000039 : TA RXR TXD RXD  [i2c1]
[  747.117861] isr: remain=20, status=0xd0000039 : TA RXR TXD RXD  [i2c1]
[  747.117870] isr: remain=8, status=0x32 : DONE TXD RXD  [i2c1]

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
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@notro @popcornmix
notro authored and popcornmix committed Jan 7, 2018
1 parent fdd1e16 commit 0a48355
Showing 1 changed file with 98 additions and 1 deletion.
99 changes: 98 additions & 1 deletion drivers/i2c/busses/i2c-bcm2835.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,18 @@
#define BCM2835_I2C_CDIV_MIN 0x0002
#define BCM2835_I2C_CDIV_MAX 0xFFFE

static unsigned int debug;
module_param(debug, uint, 0644);
MODULE_PARM_DESC(debug, "1=err, 2=isr, 3=xfer");

#define BCM2835_DEBUG_MAX 512
struct bcm2835_debug {
struct i2c_msg *msg;
int msg_idx;
size_t remain;
u32 status;
};

struct bcm2835_i2c_dev {
struct device *dev;
void __iomem *regs;
Expand All @@ -66,8 +78,78 @@ struct bcm2835_i2c_dev {
u32 msg_err;
u8 *msg_buf;
size_t msg_buf_remaining;
struct bcm2835_debug debug[BCM2835_DEBUG_MAX];
unsigned int debug_num;
unsigned int debug_num_msgs;
};

static inline void bcm2835_debug_add(struct bcm2835_i2c_dev *i2c_dev, u32 s)
{
if (!i2c_dev->debug_num_msgs || i2c_dev->debug_num >= BCM2835_DEBUG_MAX)
return;

i2c_dev->debug[i2c_dev->debug_num].msg = i2c_dev->curr_msg;
i2c_dev->debug[i2c_dev->debug_num].msg_idx =
i2c_dev->debug_num_msgs - i2c_dev->num_msgs;
i2c_dev->debug[i2c_dev->debug_num].remain = i2c_dev->msg_buf_remaining;
i2c_dev->debug[i2c_dev->debug_num].status = s;
i2c_dev->debug_num++;
}

static void bcm2835_debug_print_status(struct bcm2835_i2c_dev *i2c_dev,
struct bcm2835_debug *d)
{
u32 s = d->status;

pr_info("isr: remain=%zu, status=0x%x : %s%s%s%s%s%s%s%s%s%s [i2c%d]\n",
d->remain, s,
s & BCM2835_I2C_S_TA ? "TA " : "",
s & BCM2835_I2C_S_DONE ? "DONE " : "",
s & BCM2835_I2C_S_TXW ? "TXW " : "",
s & BCM2835_I2C_S_RXR ? "RXR " : "",
s & BCM2835_I2C_S_TXD ? "TXD " : "",
s & BCM2835_I2C_S_RXD ? "RXD " : "",
s & BCM2835_I2C_S_TXE ? "TXE " : "",
s & BCM2835_I2C_S_RXF ? "RXF " : "",
s & BCM2835_I2C_S_ERR ? "ERR " : "",
s & BCM2835_I2C_S_CLKT ? "CLKT " : "",
i2c_dev->adapter.nr);
}

static void bcm2835_debug_print_msg(struct bcm2835_i2c_dev *i2c_dev,
struct i2c_msg *msg, int i, int total,
const char *fname)
{
pr_info("%s: msg(%d/%d) %s addr=0x%02x, len=%u flags=%s%s%s%s%s%s%s [i2c%d]\n",
fname, i, total,
msg->flags & I2C_M_RD ? "read" : "write", msg->addr, msg->len,
msg->flags & I2C_M_TEN ? "TEN" : "",
msg->flags & I2C_M_RECV_LEN ? "RECV_LEN" : "",
msg->flags & I2C_M_NO_RD_ACK ? "NO_RD_ACK" : "",
msg->flags & I2C_M_IGNORE_NAK ? "IGNORE_NAK" : "",
msg->flags & I2C_M_REV_DIR_ADDR ? "REV_DIR_ADDR" : "",
msg->flags & I2C_M_NOSTART ? "NOSTART" : "",
msg->flags & I2C_M_STOP ? "STOP" : "",
i2c_dev->adapter.nr);
}

static void bcm2835_debug_print(struct bcm2835_i2c_dev *i2c_dev)
{
struct bcm2835_debug *d;
unsigned int i;

for (i = 0; i < i2c_dev->debug_num; i++) {
d = &i2c_dev->debug[i];
if (d->status == ~0)
bcm2835_debug_print_msg(i2c_dev, d->msg, d->msg_idx,
i2c_dev->debug_num_msgs, "start_transfer");
else
bcm2835_debug_print_status(i2c_dev, d);
}
if (i2c_dev->debug_num >= BCM2835_DEBUG_MAX)
pr_info("BCM2835_DEBUG_MAX reached\n");
}

static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
u32 reg, u32 val)
{
Expand Down Expand Up @@ -170,6 +252,7 @@ static void bcm2835_i2c_start_transfer(struct bcm2835_i2c_dev *i2c_dev)
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
bcm2835_debug_add(i2c_dev, ~0);
}

/*
Expand All @@ -187,6 +270,7 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
u32 val, err;

val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
bcm2835_debug_add(i2c_dev, val);

err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
if (err) {
Expand Down Expand Up @@ -253,6 +337,13 @@ static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
unsigned long time_left;
int i, ret;

if (debug)
i2c_dev->debug_num_msgs = num;

if (debug > 2)
for (i = 0; i < num; i++)
bcm2835_debug_print_msg(i2c_dev, &msgs[i], i + 1, num, __func__);

for (i = 0; i < (num - 1); i++)
if (msgs[i].flags & I2C_M_RD) {
dev_warn_once(i2c_dev->dev,
Expand All @@ -272,6 +363,10 @@ static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],

time_left = wait_for_completion_timeout(&i2c_dev->completion,
adap->timeout);
if (debug > 1 || (debug && (!time_left || i2c_dev->msg_err)))
bcm2835_debug_print(i2c_dev);
i2c_dev->debug_num_msgs = 0;
i2c_dev->debug_num = 0;
if (!time_left) {
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C,
BCM2835_I2C_C_CLEAR);
Expand All @@ -282,7 +377,9 @@ static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
if (!i2c_dev->msg_err)
return num;

dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
if (debug)
dev_err(i2c_dev->dev, "i2c transfer failed: %x\n",
i2c_dev->msg_err);

if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
return -EREMOTEIO;
Expand Down

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