drm/bridge: tc358768: Clean up clock period code

The driver defines TC358768_PRECISION as 1000, and uses "nsk" to refer
to clock periods. The original author does not remember where all this
came from. Effectively the driver is using picoseconds as the unit for
clock periods, yet referring to them by "nsk".

Clean this up by just saying the periods are in picoseconds.

Reviewed-by: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Tested-by: Maxim Schwalm <maxim.schwalm@gmail.com> # Asus TF700T
Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230906-tc358768-v4-10-31725f008a50@ideasonboard.com

1 files changed, 29 insertions, 31 deletions

diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c
index 0f117d673b14..9ce8d120b50c 100644
--- a/drivers/gpu/drm/bridge/tc358768.c
+++ b/drivers/gpu/drm/bridge/tc358768.c
@@ -15,6 +15,7 @@
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
+#include <linux/units.h>
 
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_drv.h>
@@ -627,15 +628,14 @@ static int tc358768_setup_pll(struct tc358768_priv *priv,
 	return tc358768_clear_error(priv);
 }
 
-#define TC358768_PRECISION	1000
-static u32 tc358768_ns_to_cnt(u32 ns, u32 period_nsk)
+static u32 tc358768_ns_to_cnt(u32 ns, u32 period_ps)
 {
-	return (ns * TC358768_PRECISION + period_nsk) / period_nsk;
+	return (ns * 1000 + period_ps) / period_ps;
 }
 
-static u32 tc358768_to_ns(u32 nsk)
+static u32 tc358768_ps_to_ns(u32 ps)
 {
-	return (nsk / TC358768_PRECISION);
+	return ps / 1000;
 }
 
 static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
@@ -646,7 +646,7 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
 	u32 val, val2, lptxcnt, hact, data_type;
 	s32 raw_val;
 	const struct drm_display_mode *mode;
-	u32 hsbyteclk_nsk, dsiclk_nsk, ui_nsk;
+	u32 hsbyteclk_ps, dsiclk_ps, ui_ps;
 	u32 dsiclk, hsbyteclk, video_start;
 	const u32 internal_delay = 40;
 	int ret, i;
@@ -730,67 +730,65 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
 		tc358768_write(priv, TC358768_D0W_CNTRL + i * 4, 0x0000);
 
 	/* DSI Timings */
-	hsbyteclk_nsk = (u32)div_u64((u64)1000000000 * TC358768_PRECISION,
-				  hsbyteclk);
-	dsiclk_nsk = (u32)div_u64((u64)1000000000 * TC358768_PRECISION, dsiclk);
-	ui_nsk = dsiclk_nsk / 2;
-	dev_dbg(dev, "dsiclk_nsk: %u\n", dsiclk_nsk);
-	dev_dbg(dev, "ui_nsk: %u\n", ui_nsk);
-	dev_dbg(dev, "hsbyteclk_nsk: %u\n", hsbyteclk_nsk);
+	hsbyteclk_ps = (u32)div_u64(PICO, hsbyteclk);
+	dsiclk_ps = (u32)div_u64(PICO, dsiclk);
+	ui_ps = dsiclk_ps / 2;
+	dev_dbg(dev, "dsiclk: %u ps, ui %u ps, hsbyteclk %u ps\n", dsiclk_ps,
+		ui_ps, hsbyteclk_ps);
 
 	/* LP11 > 100us for D-PHY Rx Init */
-	val = tc358768_ns_to_cnt(100 * 1000, hsbyteclk_nsk) - 1;
+	val = tc358768_ns_to_cnt(100 * 1000, hsbyteclk_ps) - 1;
 	dev_dbg(dev, "LINEINITCNT: %u\n", val);
 	tc358768_write(priv, TC358768_LINEINITCNT, val);
 
 	/* LPTimeCnt > 50ns */
-	val = tc358768_ns_to_cnt(50, hsbyteclk_nsk) - 1;
+	val = tc358768_ns_to_cnt(50, hsbyteclk_ps) - 1;
 	lptxcnt = val;
 	dev_dbg(dev, "LPTXTIMECNT: %u\n", val);
 	tc358768_write(priv, TC358768_LPTXTIMECNT, val);
 
 	/* 38ns < TCLK_PREPARE < 95ns */
-	val = tc358768_ns_to_cnt(65, hsbyteclk_nsk) - 1;
+	val = tc358768_ns_to_cnt(65, hsbyteclk_ps) - 1;
 	dev_dbg(dev, "TCLK_PREPARECNT %u\n", val);
 	/* TCLK_PREPARE + TCLK_ZERO > 300ns */
-	val2 = tc358768_ns_to_cnt(300 - tc358768_to_ns(2 * ui_nsk),
-				  hsbyteclk_nsk) - 2;
+	val2 = tc358768_ns_to_cnt(300 - tc358768_ps_to_ns(2 * ui_ps),
+				  hsbyteclk_ps) - 2;
 	dev_dbg(dev, "TCLK_ZEROCNT %u\n", val2);
 	val |= val2 << 8;
 	tc358768_write(priv, TC358768_TCLK_HEADERCNT, val);
 
 	/* TCLK_TRAIL > 60ns AND TEOT <= 105 ns + 12*UI */
-	raw_val = tc358768_ns_to_cnt(60 + tc358768_to_ns(2 * ui_nsk), hsbyteclk_nsk) - 5;
+	raw_val = tc358768_ns_to_cnt(60 + tc358768_ps_to_ns(2 * ui_ps), hsbyteclk_ps) - 5;
 	val = clamp(raw_val, 0, 127);
 	dev_dbg(dev, "TCLK_TRAILCNT: %u\n", val);
 	tc358768_write(priv, TC358768_TCLK_TRAILCNT, val);
 
 	/* 40ns + 4*UI < THS_PREPARE < 85ns + 6*UI */
-	val = 50 + tc358768_to_ns(4 * ui_nsk);
-	val = tc358768_ns_to_cnt(val, hsbyteclk_nsk) - 1;
+	val = 50 + tc358768_ps_to_ns(4 * ui_ps);
+	val = tc358768_ns_to_cnt(val, hsbyteclk_ps) - 1;
 	dev_dbg(dev, "THS_PREPARECNT %u\n", val);
 	/* THS_PREPARE + THS_ZERO > 145ns + 10*UI */
-	raw_val = tc358768_ns_to_cnt(145 - tc358768_to_ns(3 * ui_nsk), hsbyteclk_nsk) - 10;
+	raw_val = tc358768_ns_to_cnt(145 - tc358768_ps_to_ns(3 * ui_ps), hsbyteclk_ps) - 10;
 	val2 = clamp(raw_val, 0, 127);
 	dev_dbg(dev, "THS_ZEROCNT %u\n", val2);
 	val |= val2 << 8;
 	tc358768_write(priv, TC358768_THS_HEADERCNT, val);
 
 	/* TWAKEUP > 1ms in lptxcnt steps */
-	val = tc358768_ns_to_cnt(1020000, hsbyteclk_nsk);
+	val = tc358768_ns_to_cnt(1020000, hsbyteclk_ps);
 	val = val / (lptxcnt + 1) - 1;
 	dev_dbg(dev, "TWAKEUP: %u\n", val);
 	tc358768_write(priv, TC358768_TWAKEUP, val);
 
 	/* TCLK_POSTCNT > 60ns + 52*UI */
-	val = tc358768_ns_to_cnt(60 + tc358768_to_ns(52 * ui_nsk),
-				 hsbyteclk_nsk) - 3;
+	val = tc358768_ns_to_cnt(60 + tc358768_ps_to_ns(52 * ui_ps),
+				 hsbyteclk_ps) - 3;
 	dev_dbg(dev, "TCLK_POSTCNT: %u\n", val);
 	tc358768_write(priv, TC358768_TCLK_POSTCNT, val);
 
 	/* max(60ns + 4*UI, 8*UI) < THS_TRAILCNT < 105ns + 12*UI */
-	raw_val = tc358768_ns_to_cnt(60 + tc358768_to_ns(18 * ui_nsk),
-				     hsbyteclk_nsk) - 4;
+	raw_val = tc358768_ns_to_cnt(60 + tc358768_ps_to_ns(18 * ui_ps),
+				     hsbyteclk_ps) - 4;
 	val = clamp(raw_val, 0, 15);
 	dev_dbg(dev, "THS_TRAILCNT: %u\n", val);
 	tc358768_write(priv, TC358768_THS_TRAILCNT, val);
@@ -804,11 +802,11 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
 		       (mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS) ? 0 : BIT(0));
 
 	/* TXTAGOCNT[26:16] RXTASURECNT[10:0] */
-	val = tc358768_to_ns((lptxcnt + 1) * hsbyteclk_nsk * 4);
-	val = tc358768_ns_to_cnt(val, hsbyteclk_nsk) / 4 - 1;
+	val = tc358768_ps_to_ns((lptxcnt + 1) * hsbyteclk_ps * 4);
+	val = tc358768_ns_to_cnt(val, hsbyteclk_ps) / 4 - 1;
 	dev_dbg(dev, "TXTAGOCNT: %u\n", val);
-	val2 = tc358768_ns_to_cnt(tc358768_to_ns((lptxcnt + 1) * hsbyteclk_nsk),
-				  hsbyteclk_nsk) - 2;
+	val2 = tc358768_ns_to_cnt(tc358768_ps_to_ns((lptxcnt + 1) * hsbyteclk_ps),
+				  hsbyteclk_ps) - 2;
 	dev_dbg(dev, "RXTASURECNT: %u\n", val2);
 	val = val << 16 | val2;
 	tc358768_write(priv, TC358768_BTACNTRL1, val);