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drivers: pn532_i2c: Add retry on error mechanism

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Currently, we very occasionally can EXNIO errors from pn532_i2c_write() ->
i2c_write() -> write(). This may happen about once every 30 seconds.
Based from the kernel sources, EXNIO happens if the chip no longer
responds to its own address.

To make sure we do not loose any sent packets, we retry to send
PN532_SEND_RETRIES number of times. Since we miss 1 every 30 or so
seconds, doing 1 retry should be fine.

This might be considered a hack as the failure may be some other timing
related issue.

Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>
This commit is contained in:
Olliver Schinagl 2016-10-24 09:34:19 +02:00
parent 8f8f780c2b
commit d960673681
1 changed files with 15 additions and 1 deletions
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14
libnfc/drivers/pn532_i2c.c
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@ -59,6 +59,13 @@
// I2C address of the PN532 chip. // I2C address of the PN532 chip.
#define PN532_I2C_ADDR 0x24 #define PN532_I2C_ADDR 0x24
/*
* When sending lots of data, the pn532 occasionally fails to respond in time.
* Since it happens so rarely, lets try to fix it by re-sending the data. This
* define allows for fine tuning the number of retries.
*/
#define PN532_SEND_RETRIES 3
// Internal data structs // Internal data structs
const struct pn53x_io pn532_i2c_io; const struct pn53x_io pn532_i2c_io;
@ -368,6 +375,7 @@ static int
pn532_i2c_send(nfc_device *pnd, const uint8_t *pbtData, const size_t szData, int timeout) pn532_i2c_send(nfc_device *pnd, const uint8_t *pbtData, const size_t szData, int timeout)
{ {
int res = 0; int res = 0;
uint8_t retries;
// Discard any existing data ? // Discard any existing data ?
@ -403,7 +411,13 @@ pn532_i2c_send(nfc_device *pnd, const uint8_t *pbtData, const size_t szData, int
return pnd->last_error; return pnd->last_error;
} }
for (retries = PN532_SEND_RETRIES; retries > 0; retries--) {
res = pn532_i2c_write(DRIVER_DATA(pnd)->dev, abtFrame, szFrame); res = pn532_i2c_write(DRIVER_DATA(pnd)->dev, abtFrame, szFrame);
if (res >= 0)
break;
log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_ERROR, "Failed to transmit data. Retries left: %d.", retries - 1);
}
if (res < 0) { if (res < 0) {
log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_ERROR, "%s", "Unable to transmit data. (TX)"); log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_ERROR, "%s", "Unable to transmit data. (TX)");