linux-kernel - Re: [PATCH] ALSA: hda: Fix tegra hda dp infoframe struct

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Date:   Tue, 13 Sep 2022 07:40:36 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Mohan Kumar <mkumard@...dia.com>
Cc:     <tiwai@...e.com>, <perex@...ex.cz>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <linux-tegra@...r.kernel.org>,
        <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ALSA: hda: Fix tegra hda dp infoframe struct

On Tue, 13 Sep 2022 05:44:10 +0200,
Mohan Kumar wrote:
> 
> Tegra HDA HW expects infoframe data bytes order same for both
> HDMI and DP i.e infoframe data starts from 5th bytes offset.
> This hw behavior mandates to have dummy bytes for dp infoframe
> structure for Tegra.
> 
> Signed-off-by: Mohan Kumar <mkumard@...dia.com>
> ---
>  sound/pci/hda/patch_hdmi.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
> index 6c209cd26c0c..a52e764db2e0 100644
> --- a/sound/pci/hda/patch_hdmi.c
> +++ b/sound/pci/hda/patch_hdmi.c
> @@ -218,6 +218,9 @@ struct dp_audio_infoframe {
>  	u8 type; /* 0x84 */
>  	u8 len;  /* 0x1b */
>  	u8 ver;  /* 0x11 << 2 */
> +#if IS_ENABLED(CONFIG_SND_HDA_TEGRA)
> +	u8 checksum; /* Tegra HW expects infoframe bytes from 5th offset */
> +#endif

I'm afraid that we can't use ifdef here, as this is another module
that is used not only by snd-hda-tegra.  In theory, snd-hda-intel can
run on Arm using the same codec driver.

That is, the check has to be dynamically.  Maybe we need to set a flag
at tegra_hdmi_init().

If I understand correctly, Tegra uses the same byte layout for both DP
and HDMI?  If so, the patch like below should work instead.

Of course, if that's really specific to Tegra, not generically for
Nvidia graphics, the flag has to be set in a different way...


thanks,

Takashi

-- 8< --
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -171,6 +171,7 @@ struct hdmi_spec {
 	/* hdmi interrupt trigger control flag for Nvidia codec */
 	bool hdmi_intr_trig_ctrl;
 	bool intel_hsw_fixup;	/* apply Intel platform-specific fixups */
+	bool tegra_dp_workaround; /* workaround DP audio infoframe for Tegra */
 	/*
 	 * Non-generic VIA/NVIDIA specific
 	 */
@@ -679,15 +680,24 @@ static void hdmi_pin_setup_infoframe(struct hda_codec *codec,
 				     int ca, int active_channels,
 				     int conn_type)
 {
+	struct hdmi_spec *spec = codec->spec;
 	union audio_infoframe ai;
 
 	memset(&ai, 0, sizeof(ai));
-	if (conn_type == 0) { /* HDMI */
+	if (conn_type == 0 || /* HDMI */
+	    /* DisplayPort for Tegra: Tegra HW expects same layout as HDMI */
+	    (conn_type == 1 && spec->tegra_dp_workaround)) {
 		struct hdmi_audio_infoframe *hdmi_ai = &ai.hdmi;
 
-		hdmi_ai->type		= 0x84;
-		hdmi_ai->ver		= 0x01;
-		hdmi_ai->len		= 0x0a;
+		if (conn_type == 0) { /* HDMI */
+			hdmi_ai->type		= 0x84;
+			hdmi_ai->ver		= 0x01;
+			hdmi_ai->len		= 0x0a;
+		} else { /* Tegra DP */
+			hdmi_ai->type		= 0x84;
+			hdmi_ai->len		= 0x1b;
+			hdmi_ai->ver		= 0x11 << 2;
+		}
 		hdmi_ai->CC02_CT47	= active_channels - 1;
 		hdmi_ai->CA		= ca;
 		hdmi_checksum_audio_infoframe(hdmi_ai);
@@ -3992,6 +4002,7 @@ static int tegra_hdmi_init(struct hda_codec *codec)
 	spec->chmap.ops.chmap_cea_alloc_validate_get_type =
 		nvhdmi_chmap_cea_alloc_validate_get_type;
 	spec->chmap.ops.chmap_validate = nvhdmi_chmap_validate;
+	spec->tegra_dp_workaround = true;
 
 	return 0;
 }