[PATCH 2/2] MFD: twl6040-codec: Avoid PLL reconfiguration when not needed

[Peter Ujfalusi]

Do not reconfigure configure the PLL in case it has been configured
already with the requested parameters.
In case of different PLL configuration do only the needed changes.
This can save considerable amount of time since we can avoid the
defined protocol (with delays) for the PLL configuration.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
---
 drivers/mfd/twl6040-core.c |  125 ++++++++++++++++++++++++++------------------
 1 files changed, 74 insertions(+), 51 deletions(-)

diff --git a/drivers/mfd/twl6040-core.c b/drivers/mfd/twl6040-core.c
index e738678..8f01c64 100644
--- a/drivers/mfd/twl6040-core.c
+++ b/drivers/mfd/twl6040-core.c
@@ -326,23 +326,38 @@ int twl6040_set_pll(struct twl6040 *twl6040, int pll_id,
 	hppllctl = twl6040_reg_read(twl6040, TWL6040_REG_HPPLLCTL);
 	lppllctl = twl6040_reg_read(twl6040, TWL6040_REG_LPPLLCTL);
 
+	/* Force full reconfiguration when the switching between PLL */
+	if (pll_id != twl6040->pll) {
+		twl6040->sysclk = 0;
+		twl6040->mclk = 0;
+	}
+
 	switch (pll_id) {
 	case TWL6040_SYSCLK_SEL_LPPLL:
 		/* low-power PLL divider */
-		switch (freq_out) {
-		case 17640000:
-			lppllctl |= TWL6040_LPLLFIN;
-			break;
-		case 19200000:
-			lppllctl &= ~TWL6040_LPLLFIN;
-			break;
-		default:
-			dev_err(twl6040->dev,
-				"freq_out %d not supported\n", freq_out);
-			ret = -EINVAL;
-			goto pll_out;
+		/* Change the sysclk configuration only if it has been canged */
+		if (twl6040->sysclk != freq_out) {
+			switch (freq_out) {
+			case 17640000:
+				lppllctl |= TWL6040_LPLLFIN;
+				break;
+			case 19200000:
+				lppllctl &= ~TWL6040_LPLLFIN;
+				break;
+			default:
+				dev_err(twl6040->dev,
+					"freq_out %d not supported\n",
+					freq_out);
+				ret = -EINVAL;
+				goto pll_out;
+			}
+			twl6040_reg_write(twl6040, TWL6040_REG_LPPLLCTL,
+					  lppllctl);
 		}
-		twl6040_reg_write(twl6040, TWL6040_REG_LPPLLCTL, lppllctl);
+
+		/* The PLL in use has not been change, we can exit */
+		if (twl6040->pll == pll_id)
+			break;
 
 		switch (freq_in) {
 		case 32768:
@@ -373,48 +388,56 @@ int twl6040_set_pll(struct twl6040 *twl6040, int pll_id,
 			goto pll_out;
 		}
 
-		hppllctl &= ~TWL6040_MCLK_MSK;
+		if (twl6040->mclk != freq_in) {
+			hppllctl &= ~TWL6040_MCLK_MSK;
+
+			switch (freq_in) {
+			case 12000000:
+				/* PLL enabled, active mode */
+				hppllctl |= TWL6040_MCLK_12000KHZ |
+					    TWL6040_HPLLENA;
+				break;
+			case 19200000:
+				/*
+				* PLL disabled
+				* (enable PLL if MCLK jitter quality
+				*  doesn't meet specification)
+				*/
+				hppllctl |= TWL6040_MCLK_19200KHZ;
+				break;
+			case 26000000:
+				/* PLL enabled, active mode */
+				hppllctl |= TWL6040_MCLK_26000KHZ |
+					    TWL6040_HPLLENA;
+				break;
+			case 38400000:
+				/* PLL enabled, active mode */
+				hppllctl |= TWL6040_MCLK_38400KHZ |
+					    TWL6040_HPLLENA;
+				break;
+			default:
+				dev_err(twl6040->dev,
+					"freq_in %d not supported\n", freq_in);
+				ret = -EINVAL;
+				goto pll_out;
+			}
 
-		switch (freq_in) {
-		case 12000000:
-			/* PLL enabled, active mode */
-			hppllctl |= TWL6040_MCLK_12000KHZ |
-				    TWL6040_HPLLENA;
-			break;
-		case 19200000:
 			/*
-			 * PLL disabled
-			 * (enable PLL if MCLK jitter quality
-			 *  doesn't meet specification)
+			 * enable clock slicer to ensure input waveform is
+			 * square
 			 */
-			hppllctl |= TWL6040_MCLK_19200KHZ;
-			break;
-		case 26000000:
-			/* PLL enabled, active mode */
-			hppllctl |= TWL6040_MCLK_26000KHZ |
-				    TWL6040_HPLLENA;
-			break;
-		case 38400000:
-			/* PLL enabled, active mode */
-			hppllctl |= TWL6040_MCLK_38400KHZ |
-				    TWL6040_HPLLENA;
-			break;
-		default:
-			dev_err(twl6040->dev,
-				"freq_in %d not supported\n", freq_in);
-			ret = -EINVAL;
-			goto pll_out;
-		}
+			hppllctl |= TWL6040_HPLLSQRENA;
 
-		/* enable clock slicer to ensure input waveform is square */
-		hppllctl |= TWL6040_HPLLSQRENA;
-
-		twl6040_reg_write(twl6040, TWL6040_REG_HPPLLCTL, hppllctl);
-		usleep_range(500, 700);
-		lppllctl |= TWL6040_HPLLSEL;
-		twl6040_reg_write(twl6040, TWL6040_REG_LPPLLCTL, lppllctl);
-		lppllctl &= ~TWL6040_LPLLENA;
-		twl6040_reg_write(twl6040, TWL6040_REG_LPPLLCTL, lppllctl);
+			twl6040_reg_write(twl6040, TWL6040_REG_HPPLLCTL,
+					  hppllctl);
+			usleep_range(500, 700);
+			lppllctl |= TWL6040_HPLLSEL;
+			twl6040_reg_write(twl6040, TWL6040_REG_LPPLLCTL,
+					  lppllctl);
+			lppllctl &= ~TWL6040_LPLLENA;
+			twl6040_reg_write(twl6040, TWL6040_REG_LPPLLCTL,
+					  lppllctl);
+		}
 		break;
 	default:
 		dev_err(twl6040->dev, "unknown pll id %d\n", pll_id);
-- 
1.7.8.rc3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/