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Subject[PATCH 5/9] drm: bridge/dw_hdmi: avoid being recursive in N calculation
Date
There's no need to be recursive when computing the N value for the ACR
packet - we can instead calculate the multiplier prior to our switch()
based lookup, and multiply the N value appropriately afterwards.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
drivers/gpu/drm/bridge/dw_hdmi.c | 25 +++++++++----------------
1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
index a8b243278774..f0e6059f818a 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.c
+++ b/drivers/gpu/drm/bridge/dw_hdmi.c
@@ -221,6 +221,12 @@ static unsigned int hdmi_compute_n(unsigned int freq, unsigned long pixel_clk,
unsigned int ratio)
{
unsigned int n = (128 * freq) / 1000;
+ unsigned int mult = 1;
+
+ while (freq > 48000) {
+ mult *= 2;
+ freq /= 2;
+ }

switch (freq) {
case 32000:
@@ -232,6 +238,7 @@ static unsigned int hdmi_compute_n(unsigned int freq, unsigned long pixel_clk,
n = 11648;
else
n = 4096;
+ n *= mult;
break;

case 44100:
@@ -243,6 +250,7 @@ static unsigned int hdmi_compute_n(unsigned int freq, unsigned long pixel_clk,
n = (ratio == 150) ? 17836 : 8918;
else
n = 6272;
+ n *= mult;
break;

case 48000:
@@ -256,22 +264,7 @@ static unsigned int hdmi_compute_n(unsigned int freq, unsigned long pixel_clk,
n = (ratio == 150) ? 11648 : 5824;
else
n = 6144;
- break;
-
- case 88200:
- n = hdmi_compute_n(44100, pixel_clk, ratio) * 2;
- break;
-
- case 96000:
- n = hdmi_compute_n(48000, pixel_clk, ratio) * 2;
- break;
-
- case 176400:
- n = hdmi_compute_n(44100, pixel_clk, ratio) * 4;
- break;
-
- case 192000:
- n = hdmi_compute_n(48000, pixel_clk, ratio) * 4;
+ n *= mult;
break;

default:
--
2.1.0


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