Commit fe9545bb authored by Benoît Monin's avatar Benoît Monin Committed by Thomas Bogendoerfer
Browse files

clk: eyeq: Adjust PLL accuracy computation 



The spread spectrum of the PLL found in eyeQ OLB is in 1/1024 parts of the
frequency, not in 1/1000, so adjust the computation of the accuracy. Also
correct the downspreading to match.

Signed-off-by: default avatarBenoît Monin <benoit.monin@bootlin.com>
Acked-by: default avatarStephen Boyd <sboyd@kernel.org>
Signed-off-by: default avatarThomas Bogendoerfer <tsbogend@alpha.franken.de>
parent 8ab1e58c

drivers/clk/clk-eyeq.c

+9 −9
Original line number Diff line number Diff line
@@ -163,7 +163,7 @@ static void eqc_pll_downshift_factors(unsigned long *mult, unsigned long *div) 
static int eqc_pll_parse_registers(u32 r0, u32 r1, unsigned long *mult,

				   unsigned long *div, unsigned long *acc)

{

	u32 spread;

	unsigned long spread;



	if (r0 & PCSR0_BYPASS) {

		*mult = 1;
@@ -195,23 +195,23 @@ static int eqc_pll_parse_registers(u32 r0, u32 r1, unsigned long *mult, 
	/*

	 * Spread spectrum.

	 *

	 * Spread is 1/1000 parts of frequency, accuracy is half of

	 * that. To get accuracy, convert to ppb (parts per billion).

	 * Spread is in 1/1024 parts of frequency. Clock accuracy

	 * is half the spread value expressed in parts per billion.

	 *

	 * acc = spread * 1e6 / 2

	 *   with acc in parts per billion and,

	 *        spread in parts per thousand.

	 * accuracy = (spread * 1e9) / (1024 * 2)

	 *

	 * Care is taken to avoid overflowing or losing precision.

	 */

	spread = FIELD_GET(PCSR1_SPREAD, r1);

	*acc = spread * 500000;

	*acc = DIV_ROUND_CLOSEST(spread * 1000000000, 1024 * 2);



	if (r1 & PCSR1_DOWN_SPREAD) {

		/*

		 * Downspreading: the central frequency is half a

		 * spread lower.

		 */

		*mult *= 2000 - spread;

		*div *= 2000;

		*mult *= 2048 - spread;

		*div *= 2048;



		/*

		 * Previous operation might overflow 32 bits. If it