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Commit dd3a5a1e authored by Sean Young's avatar Sean Young Committed by Mauro Carvalho Chehab
Browse files

[media] iguanair: explain tx carrier setup 



Just comments. No functional changes.

Signed-off-by: default avatarSean Young <sean@mess.org>
Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
parent 123a17d1

drivers/media/rc/iguanair.c

+11 −4
Original line number Diff line number Diff line
@@ -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;

	}