diff options
| author | Mark A. Greer <mgreer@animalcreek.com> | 2014-09-02 18:12:25 -0400 |
|---|---|---|
| committer | Samuel Ortiz <sameo@linux.intel.com> | 2014-09-07 17:13:43 -0400 |
| commit | 38b4eb1f7fa87079a5a40f5d2ec4b5c0c7f14a4b (patch) | |
| tree | df78df662950aa0c4f1d92a06bce1148f63a8523 | |
| parent | 4e64eff837fb682dfb2a1188fb036d75ec57375c (diff) | |
NFC: trf7970a: Recalculate driver timeout values
Some of the timeout values used in the driver
are not long enough to handle worst-case scenarios
so they need to be recalculated.
The time to wait for the FIFO to drain past the
low-watermark is now 20 ms because it can take
around 14.35 ms to send 95 bytes (127 bytes in
full FIFO minus 32 bytes where the low-watermark
interrupt will fire). 95 bytes will take around
14.35 ms at 6.62 kbps (the lowest supported bit
rate used by ISO/IEC 15693) so 20 ms should be a
safe value.
The time to wait before issuing an EOF to complete
an ISO/IEC 15693 write or lock command is 40 ms--
20 ms to drain the FIFO and another 20 ms to ensure
the wait is long enough before sending an EOF.
Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
| -rw-r--r-- | drivers/nfc/trf7970a.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/drivers/nfc/trf7970a.c b/drivers/nfc/trf7970a.c index 22485e703849..b67946c18b40 100644 --- a/drivers/nfc/trf7970a.c +++ b/drivers/nfc/trf7970a.c | |||
| @@ -83,6 +83,13 @@ | |||
| 83 | * been received and there isn't an error). The delay is 20 ms since delays | 83 | * been received and there isn't an error). The delay is 20 ms since delays |
| 84 | * of ~16 ms have been observed during testing. | 84 | * of ~16 ms have been observed during testing. |
| 85 | * | 85 | * |
| 86 | * When transmitting a frame larger than the FIFO size (127 bytes), the | ||
| 87 | * driver will wait 20 ms for the FIFO to drain past the low-watermark | ||
| 88 | * and generate an interrupt. The low-watermark set to 32 bytes so the | ||
| 89 | * interrupt should fire after 127 - 32 = 95 bytes have been sent. At | ||
| 90 | * the lowest possible bit rate (6.62 kbps for 15693), it will take up | ||
| 91 | * to ~14.35 ms so 20 ms is used for the timeout. | ||
| 92 | * | ||
| 86 | * Type 2 write and sector select commands respond with a 4-bit ACK or NACK. | 93 | * Type 2 write and sector select commands respond with a 4-bit ACK or NACK. |
| 87 | * Having only 4 bits in the FIFO won't normally generate an interrupt so | 94 | * Having only 4 bits in the FIFO won't normally generate an interrupt so |
| 88 | * driver enables the '4_bit_RX' bit of the Special Functions register 1 | 95 | * driver enables the '4_bit_RX' bit of the Special Functions register 1 |
| @@ -105,7 +112,9 @@ | |||
| 105 | * Note under Table 1-1 in section 1.6 of | 112 | * Note under Table 1-1 in section 1.6 of |
| 106 | * http://www.ti.com/lit/ug/scbu011/scbu011.pdf, that wait should be at least | 113 | * http://www.ti.com/lit/ug/scbu011/scbu011.pdf, that wait should be at least |
| 107 | * 10 ms for TI Tag-it HF-I tags; however testing has shown that is not long | 114 | * 10 ms for TI Tag-it HF-I tags; however testing has shown that is not long |
| 108 | * enough. For this reason, the driver waits 20 ms which seems to work | 115 | * enough so 20 ms is used. So the timer is set to 40 ms - 20 ms to drain |
| 116 | * up to 127 bytes in the FIFO at the lowest bit rate plus another 20 ms to | ||
| 117 | * ensure the wait is long enough before sending the EOF. This seems to work | ||
| 109 | * reliably. | 118 | * reliably. |
| 110 | */ | 119 | */ |
| 111 | 120 | ||
| @@ -131,8 +140,8 @@ | |||
| 131 | #define TRF7970A_TX_MAX (4096 - 1) | 140 | #define TRF7970A_TX_MAX (4096 - 1) |
| 132 | 141 | ||
| 133 | #define TRF7970A_WAIT_FOR_RX_DATA_TIMEOUT 20 | 142 | #define TRF7970A_WAIT_FOR_RX_DATA_TIMEOUT 20 |
| 134 | #define TRF7970A_WAIT_FOR_FIFO_DRAIN_TIMEOUT 3 | 143 | #define TRF7970A_WAIT_FOR_FIFO_DRAIN_TIMEOUT 20 |
| 135 | #define TRF7970A_WAIT_TO_ISSUE_ISO15693_EOF 20 | 144 | #define TRF7970A_WAIT_TO_ISSUE_ISO15693_EOF 40 |
| 136 | 145 | ||
| 137 | /* Guard times for various RF technologies (in us) */ | 146 | /* Guard times for various RF technologies (in us) */ |
| 138 | #define TRF7970A_GUARD_TIME_NFCA 5000 | 147 | #define TRF7970A_GUARD_TIME_NFCA 5000 |