Change in coreboot[master]: Documentation/drivers: Add notes on Realtek HW EQ

[Sean Rhodes (Code Review)]

Sean Rhodes has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/59263 )

Change subject: Documentation/drivers: Add notes on Realtek HW EQ
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Documentation/drivers: Add notes on Realtek HW EQ

Signed-off-by: Sean Rhodes 
Change-Id: Ie13f62622a4cf2b14d36728a8a4a9e3ef24d6852
---
A Documentation/drivers/realtek.md
1 file changed, 99 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/63/59263/1

diff --git a/Documentation/drivers/realtek.md b/Documentation/drivers/realtek.md
new file mode 100644
index 0000000..89cc844
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+++ b/Documentation/drivers/realtek.md
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+## Realtek 7-band Hardware Equaliser Configuration
+
+The Realtek ALC256 and several other codecs support a 7-band hardware
+equalizer. The datasheet has extensive documentation on this, as after
+it says that it supports it, it provides all the below information on
+how to configure it:
+
+```
+
+```
+As this information is extemely helpful, we wrote up the notes below on
+how to configure it. Be careful, many, many speakers were hurt, mamed
+and even killed during the creation of these notes (particularily setting
+the output to 2.5W).
+
+
+The defaults for the HW EQ are below:
+```
+0x05350000h	< Disable EQ Register
+0x05340000h	< Dont disable
+
+0x0535001d	< Left Channel
+0x05340000
+0x0535001e
+0x05340000
+
+0x05450000	< Right Channel
+0x05440000
+0x0545001d
+0x05440000
+0x0545001e
+0x05440000
+
+0x05350000	< Enable EQ Register
+0x05344000	< Dont Enable
+
+0x02050038	< AGC Settings
+0x02044901
+0x02050013
+0x0204292F
+0x02050016
+0x02044C50
+```
+
+The following settings can be configured:
+```
+Settings	Default		Min		Max
+AGC		Disabled
+Threshold:	0dB		0dB		-46.5dB
+Front Boost:	0dB		0dB		29.25dB
+Post Boost:	-11.63dB	-11.63dB	29.25dB
+
+High Pass Filter 1
+Mode: 		Boost Gain	Boost Gain	1st order Butterworth
+BW:		1000Hz		200Hz		20000Hz
+Gain:		0dB		-12dB		+12dB
+
+High Pass Filter 2
+Mode: 		Boost Gain	Boost Gain	1st order Butterworth
+BW:		1000Hz		200Hz		20000Hz
+Gain:		0dB		-12dB		+12dB
+
+Low Pass Filter
+Mode: 		Boost Gain	Boost Gain	1st order Butterworth
+BW:		1000Hz		200Hz		20000Hz
+Gain:		0dB		-12dB		+12dB
+
+Band Pass Filter 1
+Fc:		3000Hz		1000Hz		20000Hz
+BW:		1000Hz		200Hz		10000Hz
+Gain:		0dB		-12dB		+12dB
+
+Band Pass Filter 2
+Fc:		6000Hz		1000Hz		20000Hz
+BW:		1000Hz		200Hz		10000Hz
+Gain:		0dB		-12dB		+12dB
+
+Band Pass Filter 3
+Fc:		9000Hz		1000Hz		20000Hz
+BW:		1000Hz		200Hz		10000Hz
+Gain:		0dB		-12dB		+12dB
+
+Band Pass Filter 4
+Fc:		9000Hz		1000Hz		20000Hz
+BW:		1000Hz		200Hz		10000Hz
+Gain:		0dB		-12dB		+12dB
+
+Class D Amp
+Power:		2.5W		0.25W		2.5W
+Resistance:	4ohms		4ohms		8ohms
+
+EQ Output
+Left:		0dB		-12dB		+12dB
+Right:		0dB		-12dB		+12dB
+
+VARQ
+Q:		0.707		0.1		1
+
+```