diff options
| author | Sean Young <sean@mess.org> | 2014-01-20 19:10:38 -0300 |
|---|---|---|
| committer | Mauro Carvalho Chehab <m.chehab@samsung.com> | 2014-02-04 17:22:19 -0200 |
| commit | dd3a5a1e7a8723b137f2af7905db53f011fd7287 (patch) | |
| tree | 8a8694c7c932d702225b168351ca7d9a56cd8a0e /drivers/media/rc | |
| parent | 123a17d1427a2d7ad9142df1f6543c578864a0dd (diff) | |
| download | linux-dd3a5a1e7a8723b137f2af7905db53f011fd7287.tar.bz2 | |
[media] iguanair: explain tx carrier setup
Just comments. No functional changes.
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Diffstat (limited to 'drivers/media/rc')
| -rw-r--r-- | drivers/media/rc/iguanair.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/drivers/media/rc/iguanair.c b/drivers/media/rc/iguanair.c index fdae05c4f377..99a3a5a509e6 100644 --- a/drivers/media/rc/iguanair.c +++ b/drivers/media/rc/iguanair.c @@ -286,10 +286,10 @@ static int iguanair_receiver(struct iguanair *ir, bool enable) } /* - * The iguana ir creates the carrier by busy spinning after each pulse or - * space. This is counted in CPU cycles, with the CPU running at 24MHz. It is + * The iguanair creates the carrier by busy spinning after each half period. + * This is counted in CPU cycles, with the CPU running at 24MHz. It is * broken down into 7-cycles and 4-cyles delays, with a preference for - * 4-cycle delays. + * 4-cycle delays, minus the overhead of the loop itself (cycle_overhead). */ static int iguanair_set_tx_carrier(struct rc_dev *dev, uint32_t carrier) { @@ -316,7 +316,14 @@ static int iguanair_set_tx_carrier(struct rc_dev *dev, uint32_t carrier) sevens = (4 - cycles) & 3; fours = (cycles - sevens * 7) / 4; - /* magic happens here */ + /* + * The firmware interprets these values as a relative offset + * for a branch. Immediately following the branches, there + * 4 instructions of 7 cycles (2 bytes each) and 110 + * instructions of 4 cycles (1 byte each). A relative branch + * of 0 will execute all of them, branch further for less + * cycle burning. + */ ir->packet->busy7 = (4 - sevens) * 2; ir->packet->busy4 = 110 - fours; } |