* [PATCH 1/3] ALSA: doc: Document PC Beep Hidden Register on Realtek ALC256
[not found] <cover.1585553414.git.tommyhebb@gmail.com>
@ 2020-03-30 7:30 ` Thomas Hebb
2020-03-31 13:11 ` Sasha Levin
2020-03-30 7:30 ` [PATCH 2/3] ALSA: hda/realtek - Set principled PC Beep configuration for ALC256 Thomas Hebb
2020-03-30 7:30 ` [PATCH 3/3] ALSA: hda/realtek - Remove now-unnecessary XPS 13 headphone noise fixups Thomas Hebb
2 siblings, 1 reply; 5+ messages in thread
From: Thomas Hebb @ 2020-03-30 7:30 UTC (permalink / raw)
To: alsa-devel, linux-kernel
Cc: Kailang Yang, Thomas Hebb, stable, Jaroslav Kysela,
Jonathan Corbet, Takashi Iwai, linux-doc, linux-kernel
This codec (among others) has a hidden set of audio routes, apparently
designed to allow PC Beep output without a mixer widget on the output
path, which are controlled by an undocumented Realtek vendor register.
The default configuration of these routes means that certain inputs
aren't accessible, necessitating driver control of the register.
However, Realtek has provided no documentation of the register, instead
opting to fix issues by providing magic numbers, most of which have been
at least somewhat erroneous. These magic numbers then get copied by
others into model-specific fixups, leading to a fragmented and buggy set
of configurations.
To get out of this situation, I've reverse engineered the register by
flipping bits and observing how the codec's behavior changes. This
commit documents my findings. It does not change any code.
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Hebb <tommyhebb@gmail.com>
---
Documentation/sound/hd-audio/index.rst | 1 +
.../sound/hd-audio/realtek-pc-beep.rst | 129 ++++++++++++++++++
2 files changed, 130 insertions(+)
create mode 100644 Documentation/sound/hd-audio/realtek-pc-beep.rst
diff --git a/Documentation/sound/hd-audio/index.rst b/Documentation/sound/hd-audio/index.rst
index f8a72ffffe66..6e12de9fc34e 100644
--- a/Documentation/sound/hd-audio/index.rst
+++ b/Documentation/sound/hd-audio/index.rst
@@ -8,3 +8,4 @@ HD-Audio
models
controls
dp-mst
+ realtek-pc-beep
diff --git a/Documentation/sound/hd-audio/realtek-pc-beep.rst b/Documentation/sound/hd-audio/realtek-pc-beep.rst
new file mode 100644
index 000000000000..be47c6f76a6e
--- /dev/null
+++ b/Documentation/sound/hd-audio/realtek-pc-beep.rst
@@ -0,0 +1,129 @@
+===============================
+Realtek PC Beep Hidden Register
+===============================
+
+This file documents the "PC Beep Hidden Register", which is present in certain
+Realtek HDA codecs and controls a muxer and pair of passthrough mixers that can
+route audio between pins but aren't themselves exposed as HDA widgets. As far
+as I can tell, these hidden routes are designed to allow flexible PC Beep output
+for codecs that don't have mixer widgets in their output paths. Why it's easier
+to hide a mixer behind an undocumented vendor register than to just expose it
+as a widget, I have no idea.
+
+Register Description
+====================
+
+The register is accessed via processing coefficient 0x36 on NID 20h. Bits not
+identified below have no discernible effect on my machine, a Dell XPS 13 9350::
+
+ MSB LSB
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | |h|S|L| | B |R| | Known bits
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ |0|0|1|1| 0x7 |0|0x0|1| 0x7 | Reset value
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+1Ah input select (B): 2 bits
+ When zero, expose the PC Beep line (from the internal beep generator, when
+ enabled with the Set Beep Generation verb on NID 01h, or else from the
+ external PCBEEP pin) on the 1Ah pin node. When nonzero, expose the headphone
+ jack (or possibly Line In on some machines) input instead. If PC Beep is
+ selected, the 1Ah boost control has no effect.
+
+Amplify 1Ah loopback, left (L): 1 bit
+ Amplify the left channel of 1Ah before mixing it into outputs as specified
+ by h and S bits. Does not affect the level of 1Ah exposed to other widgets.
+
+Amplify 1Ah loopback, right (R): 1 bit
+ Amplify the right channel of 1Ah before mixing it into outputs as specified
+ by h and S bits. Does not affect the level of 1Ah exposed to other widgets.
+
+Loopback 1Ah to 21h [active low] (h): 1 bit
+ When zero, mix 1Ah (possibly with amplification, depending on L and R bits)
+ into 21h (headphone jack on my machine). Mixed signal respects the mute
+ setting on 21h.
+
+Loopback 1Ah to 14h (S): 1 bit
+ When one, mix 1Ah (possibly with amplification, depending on L and R bits)
+ into 14h (internal speaker on my machine). Mixed signal **ignores** the mute
+ setting on 14h and is present whenever 14h is configured as an output.
+
+Path diagrams
+=============
+
+1Ah input selection (DIV is the PC Beep divider set on NID 01h)::
+
+ <Beep generator> <PCBEEP pin> <Headphone jack>
+ | | |
+ +--DIV--+--!DIV--+ {1Ah boost control}
+ | |
+ +--(b == 0)--+--(b != 0)--+
+ |
+ >1Ah (Beep/Headphone Mic/Line In)<
+
+Loopback of 1Ah to 21h/14h::
+
+ <1Ah (Beep/Headphone Mic/Line In)>
+ |
+ {amplify if L/R}
+ |
+ +-----!h-----+-----S-----+
+ | |
+ {21h mute control} |
+ | |
+ >21h (Headphone)< >14h (Internal Speaker)<
+
+Background
+==========
+
+All Realtek HDA codecs have a vendor-defined widget with node ID 20h which
+provides access to a bank of registers that control various codec functions.
+Registers are read and written via the standard HDA processing coefficient
+verbs (Set/Get Coefficient Index, Set/Get Processing Coefficient). The node is
+named "Realtek Vendor Registers" in public datasheets' verb listings and,
+apart from that, is entirely undocumented.
+
+This particular register, exposed at coefficient 0x36 and named in commits from
+Realtek, is of note: unlike most registers, which seem to control detailed
+amplifier parameters not in scope of the HDA specification, it controls audio
+routing which could just as easily have been defined using standard HDA mixer
+and selector widgets.
+
+Specifically, it selects between two sources for the input pin widget with Node
+ID (NID) 1Ah: the widget's signal can come either from an audio jack (on my
+laptop, a Dell XPS 13 9350, it's the headphone jack, but comments in Realtek
+commits indicate that it might be a Line In on some machines) or from the PC
+Beep line (which is itself multiplexed between the codec's internal beep
+generator and external PCBEEP pin, depending on if the beep generator is
+enabled via verbs on NID 01h). Additionally, it can mix (with optional
+amplification) that signal onto the 21h and/or 14h output pins.
+
+The register's reset value is 0x3717, corresponding to PC Beep on 1Ah that is
+then amplified and mixed into both the headphones and the speakers. Not only
+does this violate the HDA specification, which says that "[a vendor defined
+beep input pin] connection may be maintained *only* while the Link reset
+(**RST#**) is asserted", it means that we cannot ignore the register if we care
+about the input that 1Ah would otherwise expose or if the PCBEEP trace is
+poorly shielded and picks up chassis noise (both of which are the case on my
+machine).
+
+Unfortunately, there are lots of ways to get this register configuration wrong.
+Linux, it seems, has gone through most of them. For one, the register resets
+after S3 suspend: judging by existing code, this isn't the case for all vendor
+registers, and it's led to some fixes that improve behavior on cold boot but
+don't last after suspend. Other fixes have successfully switched the 1Ah input
+away from PC Beep but have failed to disable both loopback paths. On my
+machine, this means that the headphone input is amplified and looped back to
+the headphone output, which uses the exact same pins! As you might expect, this
+causes terrible headphone noise, the character of which is controlled by the
+1Ah boost control. (If you've seen instructions online to fix XPS 13 headphone
+noise by changing "Headphone Mic Boost" in ALSA, now you know why.)
+
+The information here has been obtained through black-box reverse engineering of
+the ALC256 codec's behavior and is not guaranteed to be correct. It likely
+also applies for the ALC255, ALC257, ALC235, and ALC236, since those codecs
+seem to be close relatives of the ALC256. (They all share one initialization
+function.) Additionally, other codecs like the ALC225 and ALC285 also have this
+register, judging by existing fixups in ``patch_realtek.c``, but specific
+data (e.g. node IDs, bit positions, pin mappings) for those codecs may differ
+from what I've described here.
--
2.25.2
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 2/3] ALSA: hda/realtek - Set principled PC Beep configuration for ALC256
[not found] <cover.1585553414.git.tommyhebb@gmail.com>
2020-03-30 7:30 ` [PATCH 1/3] ALSA: doc: Document PC Beep Hidden Register on Realtek ALC256 Thomas Hebb
@ 2020-03-30 7:30 ` Thomas Hebb
2020-03-30 7:30 ` [PATCH 3/3] ALSA: hda/realtek - Remove now-unnecessary XPS 13 headphone noise fixups Thomas Hebb
2 siblings, 0 replies; 5+ messages in thread
From: Thomas Hebb @ 2020-03-30 7:30 UTC (permalink / raw)
To: alsa-devel, linux-kernel
Cc: Kailang Yang, Thomas Hebb, stable, Greg Kroah-Hartman, Hui Wang,
Jaroslav Kysela, Jian-Hong Pan, Michał Mirosław,
Sergey Bostandzhyan, Takashi Iwai, Tomas Espeleta, linux-kernel
The Realtek PC Beep Hidden Register[1] is currently set by
patch_realtek.c in two different places:
In alc_fill_eapd_coef(), it's set to the value 0x5757, corresponding to
non-beep input on 1Ah and no 1Ah loopback to either headphones or
speakers. (Although, curiously, the loopback amp is still enabled.) This
write was added fairly recently by commit e3743f431143 ("ALSA:
hda/realtek - Dell headphone has noise on unmute for ALC236") and is a
safe default. However, it happens in the wrong place:
alc_fill_eapd_coef() runs on module load and cold boot but not on S3
resume, meaning the register loses its value after suspend.
Conversely, in alc256_init(), the register is updated to unset bit 13
(disable speaker loopback) and set bit 5 (set non-beep input on 1Ah).
Although this write does run on S3 resume, it's not quite enough to fix
up the register's default value of 0x3717. What's missing is a set of
bit 14 to disable headphone loopback. Without that, we end up with a
feedback loop where the headphone jack is being driven by amplified
samples of itself[2].
This change eliminates the write in alc_fill_eapd_coef() and replaces
the update in alc256_init() with a write of the fixed value 0x4727. This
value ought to have the same behavior as 0x5757--disabling all PC Beep
routing that isn't part of the HDA node graph--but it has two
differences:
1. To enable non-beep input on 1Ah, the `b` field is set to 1, like the
previous code in alc256_init() used, instead of 2, like the value
written by alc_fill_eapd_coef() used. My testing shows these two
values to behave identically, but, in case there is a difference,
a bitwise update of the register seems like a more reliable source
of truth than a magic number written without explanation.
2. Loopback amplification is disabled (unset L and R bits) because no
loopback path is in use.
Affects the ALC255, ALC256, ALC257, ALC235, and ALC236 codecs.
[1] Newly documented in Documentation/sound/hd-audio/realtek-pc-beep.rst
[2] Setting the "Headphone Mic Boost" control from userspace changes
this feedback loop and has been a widely-shared workaround for headphone
noise on laptops like the Dell XPS 13 9350. This commit eliminates the
feedback loop and makes the workaround unnecessary.
Fixes: e3743f431143 ("ALSA: hda/realtek - Dell headphone has noise on unmute for ALC236")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Hebb <tommyhebb@gmail.com>
---
sound/pci/hda/patch_realtek.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/sound/pci/hda/patch_realtek.c b/sound/pci/hda/patch_realtek.c
index 63e1a56f705b..024dd61a788b 100644
--- a/sound/pci/hda/patch_realtek.c
+++ b/sound/pci/hda/patch_realtek.c
@@ -367,7 +367,9 @@ static void alc_fill_eapd_coef(struct hda_codec *codec)
case 0x10ec0215:
case 0x10ec0233:
case 0x10ec0235:
+ case 0x10ec0236:
case 0x10ec0255:
+ case 0x10ec0256:
case 0x10ec0257:
case 0x10ec0282:
case 0x10ec0283:
@@ -379,11 +381,6 @@ static void alc_fill_eapd_coef(struct hda_codec *codec)
case 0x10ec0300:
alc_update_coef_idx(codec, 0x10, 1<<9, 0);
break;
- case 0x10ec0236:
- case 0x10ec0256:
- alc_write_coef_idx(codec, 0x36, 0x5757);
- alc_update_coef_idx(codec, 0x10, 1<<9, 0);
- break;
case 0x10ec0275:
alc_update_coef_idx(codec, 0xe, 0, 1<<0);
break;
@@ -3269,7 +3266,13 @@ static void alc256_init(struct hda_codec *codec)
alc_update_coefex_idx(codec, 0x57, 0x04, 0x0007, 0x4); /* Hight power */
alc_update_coefex_idx(codec, 0x53, 0x02, 0x8000, 1 << 15); /* Clear bit */
alc_update_coefex_idx(codec, 0x53, 0x02, 0x8000, 0 << 15);
- alc_update_coef_idx(codec, 0x36, 1 << 13, 1 << 5); /* Switch pcbeep path to Line in path*/
+ /*
+ * Expose headphone mic (or possibly Line In on some machines) instead
+ * of PC Beep on 1Ah, and disable 1Ah loopback for all outputs. See
+ * Documentation/sound/hd-audio/realtek-pc-beep.rst for details of
+ * this register.
+ */
+ alc_write_coef_idx(codec, 0x36, 0x4727);
}
static void alc256_shutup(struct hda_codec *codec)
--
2.25.2
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 3/3] ALSA: hda/realtek - Remove now-unnecessary XPS 13 headphone noise fixups
[not found] <cover.1585553414.git.tommyhebb@gmail.com>
2020-03-30 7:30 ` [PATCH 1/3] ALSA: doc: Document PC Beep Hidden Register on Realtek ALC256 Thomas Hebb
2020-03-30 7:30 ` [PATCH 2/3] ALSA: hda/realtek - Set principled PC Beep configuration for ALC256 Thomas Hebb
@ 2020-03-30 7:30 ` Thomas Hebb
2020-03-31 13:11 ` Sasha Levin
2 siblings, 1 reply; 5+ messages in thread
From: Thomas Hebb @ 2020-03-30 7:30 UTC (permalink / raw)
To: alsa-devel, linux-kernel
Cc: Kailang Yang, Thomas Hebb, stable, Hui Wang, Jaroslav Kysela,
Jian-Hong Pan, Jonathan Corbet, Kai-Heng Feng,
Michał Mirosław, Sergey Bostandzhyan, Takashi Iwai,
Tomas Espeleta, linux-doc, linux-kernel
patch_realtek.c has historically failed to properly configure the PC
Beep Hidden Register for the ALC256 codec (among others). Depending on
your kernel version, symptoms of this misconfiguration can range from
chassis noise, picked up by a poorly-shielded PCBEEP trace, getting
amplified and played on your internal speaker and/or headphones to loud
feedback, which responds to the "Headphone Mic Boost" ALSA control,
getting played through your headphones. For details of the problem, see
the patch in this series titled "ALSA: hda/realtek - Set principled PC
Beep configuration for ALC256", which fixes the configuration.
These symptoms have been most noticed on the Dell XPS 13 9350 and 9360,
popular laptops that use the ALC256. As a result, several model-specific
fixups have been introduced to try and fix the problem, the most
egregious of which locks the "Headphone Mic Boost" control as a hack to
minimize noise from a feedback loop that shouldn't have been there in
the first place.
Now that the underlying issue has been fixed, remove all these fixups.
Remaining fixups needed by the XPS 13 are all picked up by existing pin
quirks.
This change should, for the XPS 13 9350/9360
- Significantly increase volume and audio quality on headphones
- Eliminate headphone popping on suspend/resume
- Allow "Headphone Mic Boost" to be set again, making the headphone
jack fully usable as a microphone jack too.
Fixes: 8c69729b4439 ("ALSA: hda - Fix headphone noise after Dell XPS 13 resume back from S3")
Fixes: 423cd785619a ("ALSA: hda - Fix headphone noise on Dell XPS 13 9360")
Fixes: e4c9fd10eb21 ("ALSA: hda - Apply headphone noise quirk for another Dell XPS 13 variant")
Fixes: 1099f48457d0 ("ALSA: hda/realtek: Reduce the Headphone static noise on XPS 9350/9360")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Hebb <tommyhebb@gmail.com>
---
Documentation/sound/hd-audio/models.rst | 2 --
sound/pci/hda/patch_realtek.c | 34 -------------------------
2 files changed, 36 deletions(-)
diff --git a/Documentation/sound/hd-audio/models.rst b/Documentation/sound/hd-audio/models.rst
index 11298f0ce44d..0ea967d34583 100644
--- a/Documentation/sound/hd-audio/models.rst
+++ b/Documentation/sound/hd-audio/models.rst
@@ -216,8 +216,6 @@ alc298-dell-aio
ALC298 fixups on Dell AIO machines
alc275-dell-xps
ALC275 fixups on Dell XPS models
-alc256-dell-xps13
- ALC256 fixups on Dell XPS13
lenovo-spk-noise
Workaround for speaker noise on Lenovo machines
lenovo-hotkey
diff --git a/sound/pci/hda/patch_realtek.c b/sound/pci/hda/patch_realtek.c
index 024dd61a788b..a57581ddcc0c 100644
--- a/sound/pci/hda/patch_realtek.c
+++ b/sound/pci/hda/patch_realtek.c
@@ -5378,17 +5378,6 @@ static void alc271_hp_gate_mic_jack(struct hda_codec *codec,
}
}
-static void alc256_fixup_dell_xps_13_headphone_noise2(struct hda_codec *codec,
- const struct hda_fixup *fix,
- int action)
-{
- if (action != HDA_FIXUP_ACT_PRE_PROBE)
- return;
-
- snd_hda_codec_amp_stereo(codec, 0x1a, HDA_INPUT, 0, HDA_AMP_VOLMASK, 1);
- snd_hda_override_wcaps(codec, 0x1a, get_wcaps(codec, 0x1a) & ~AC_WCAP_IN_AMP);
-}
-
static void alc269_fixup_limit_int_mic_boost(struct hda_codec *codec,
const struct hda_fixup *fix,
int action)
@@ -5866,8 +5855,6 @@ enum {
ALC298_FIXUP_DELL1_MIC_NO_PRESENCE,
ALC298_FIXUP_DELL_AIO_MIC_NO_PRESENCE,
ALC275_FIXUP_DELL_XPS,
- ALC256_FIXUP_DELL_XPS_13_HEADPHONE_NOISE,
- ALC256_FIXUP_DELL_XPS_13_HEADPHONE_NOISE2,
ALC293_FIXUP_LENOVO_SPK_NOISE,
ALC233_FIXUP_LENOVO_LINE2_MIC_HOTKEY,
ALC255_FIXUP_DELL_SPK_NOISE,
@@ -6607,23 +6594,6 @@ static const struct hda_fixup alc269_fixups[] = {
{}
}
},
- [ALC256_FIXUP_DELL_XPS_13_HEADPHONE_NOISE] = {
- .type = HDA_FIXUP_VERBS,
- .v.verbs = (const struct hda_verb[]) {
- /* Disable pass-through path for FRONT 14h */
- {0x20, AC_VERB_SET_COEF_INDEX, 0x36},
- {0x20, AC_VERB_SET_PROC_COEF, 0x1737},
- {}
- },
- .chained = true,
- .chain_id = ALC255_FIXUP_DELL1_MIC_NO_PRESENCE
- },
- [ALC256_FIXUP_DELL_XPS_13_HEADPHONE_NOISE2] = {
- .type = HDA_FIXUP_FUNC,
- .v.func = alc256_fixup_dell_xps_13_headphone_noise2,
- .chained = true,
- .chain_id = ALC256_FIXUP_DELL_XPS_13_HEADPHONE_NOISE
- },
[ALC293_FIXUP_LENOVO_SPK_NOISE] = {
.type = HDA_FIXUP_FUNC,
.v.func = alc_fixup_disable_aamix,
@@ -7117,17 +7087,14 @@ static const struct snd_pci_quirk alc269_fixup_tbl[] = {
SND_PCI_QUIRK(0x1028, 0x06de, "Dell", ALC293_FIXUP_DISABLE_AAMIX_MULTIJACK),
SND_PCI_QUIRK(0x1028, 0x06df, "Dell", ALC293_FIXUP_DISABLE_AAMIX_MULTIJACK),
SND_PCI_QUIRK(0x1028, 0x06e0, "Dell", ALC293_FIXUP_DISABLE_AAMIX_MULTIJACK),
- SND_PCI_QUIRK(0x1028, 0x0704, "Dell XPS 13 9350", ALC256_FIXUP_DELL_XPS_13_HEADPHONE_NOISE2),
SND_PCI_QUIRK(0x1028, 0x0706, "Dell Inspiron 7559", ALC256_FIXUP_DELL_INSPIRON_7559_SUBWOOFER),
SND_PCI_QUIRK(0x1028, 0x0725, "Dell Inspiron 3162", ALC255_FIXUP_DELL_SPK_NOISE),
SND_PCI_QUIRK(0x1028, 0x0738, "Dell Precision 5820", ALC269_FIXUP_NO_SHUTUP),
- SND_PCI_QUIRK(0x1028, 0x075b, "Dell XPS 13 9360", ALC256_FIXUP_DELL_XPS_13_HEADPHONE_NOISE2),
SND_PCI_QUIRK(0x1028, 0x075c, "Dell XPS 27 7760", ALC298_FIXUP_SPK_VOLUME),
SND_PCI_QUIRK(0x1028, 0x075d, "Dell AIO", ALC298_FIXUP_SPK_VOLUME),
SND_PCI_QUIRK(0x1028, 0x07b0, "Dell Precision 7520", ALC295_FIXUP_DISABLE_DAC3),
SND_PCI_QUIRK(0x1028, 0x0798, "Dell Inspiron 17 7000 Gaming", ALC256_FIXUP_DELL_INSPIRON_7559_SUBWOOFER),
SND_PCI_QUIRK(0x1028, 0x080c, "Dell WYSE", ALC225_FIXUP_DELL_WYSE_MIC_NO_PRESENCE),
- SND_PCI_QUIRK(0x1028, 0x082a, "Dell XPS 13 9360", ALC256_FIXUP_DELL_XPS_13_HEADPHONE_NOISE2),
SND_PCI_QUIRK(0x1028, 0x084b, "Dell", ALC274_FIXUP_DELL_AIO_LINEOUT_VERB),
SND_PCI_QUIRK(0x1028, 0x084e, "Dell", ALC274_FIXUP_DELL_AIO_LINEOUT_VERB),
SND_PCI_QUIRK(0x1028, 0x0871, "Dell Precision 3630", ALC255_FIXUP_DELL_HEADSET_MIC),
@@ -7480,7 +7447,6 @@ static const struct hda_model_fixup alc269_fixup_models[] = {
{.id = ALC298_FIXUP_DELL1_MIC_NO_PRESENCE, .name = "alc298-dell1"},
{.id = ALC298_FIXUP_DELL_AIO_MIC_NO_PRESENCE, .name = "alc298-dell-aio"},
{.id = ALC275_FIXUP_DELL_XPS, .name = "alc275-dell-xps"},
- {.id = ALC256_FIXUP_DELL_XPS_13_HEADPHONE_NOISE, .name = "alc256-dell-xps13"},
{.id = ALC293_FIXUP_LENOVO_SPK_NOISE, .name = "lenovo-spk-noise"},
{.id = ALC233_FIXUP_LENOVO_LINE2_MIC_HOTKEY, .name = "lenovo-hotkey"},
{.id = ALC255_FIXUP_DELL_SPK_NOISE, .name = "dell-spk-noise"},
--
2.25.2
^ permalink raw reply related [flat|nested] 5+ messages in thread