Linux/DRA746: HDMI: cable detection not working when interfacing with DS90UB949

Francesco Valla

Part Number: DRA746
Other Parts Discussed in Thread: DRA744, PCF8575, TPD12S016

Tool/software: Linux

Hi,

I'm working on a custom board based on DRA744.

While the HDMI part is working fine when using an external HDMI display connected with a standard cable, we're having issues with interfacing with a DS90UB949 HDMI-to-FPDlink III serializer.

The DDC link is working fine - in fact, I can upload a custom EDID on the serializer and have it read by the HDMI driver. Still, no signal is output on TMDS lines. Debugging the problem, I found that HDMI IRQs are triggered correctly when using the cable (at startup and at every connection/disconnection) but not when the processor is directly interfaced with the DS90UB949. In this last case, only one single interrupt is triggered with both HDMI_IRQ_LINK_CONNECT and HDMI_IRQ_LINK_DISCONNECT bits set - but no more.

How the cable detection is performed internally? What is the RXDET line the driver is referring to? As a workaround, can I force this detection?

Thank you

Br,

Franecsco valla

over 7 years ago

0 Yordan Kamenov over 7 years ago

TI__Mastermind 42515 points

Hi Franecsco,

which SDK you use?

Regards,
Yordan

0 Francesco Valla over 7 years ago in reply to Yordan Kamenov

Intellectual 570 points

Hi,
I'm on Processor SDK Linux Automotive 3.01.00.03

Regrads,
Francesco

0 Yordan Kamenov over 7 years ago in reply to Francesco Valla

TI__Mastermind 42515 points

Hi Francesco,

I have forwarded your question to HDMI expert to comment.

Regards,
Yordan

0 Venkat Mandela over 7 years ago in reply to Yordan Kamenov

TI__Expert 5850 points

Hi Franseco,

On the EVM, we rely on the output of the HPD signal coming from tpd12s016 connected to a PCF8575 GPIO expander to provide the HDMI hotplug status. We do not rely on the connect/disconnect IRQ's.

I will check if there are patches to force HDMI output.

regards,
Venkat

0 Francesco Valla over 7 years ago in reply to Venkat Mandela

Intellectual 570 points

Hi Venkat,
currently, the connect/disconnect interrupt is used internally by the driver released by TI to set the power mode for the HDMI block (OFF, LDOON or TXON).

While we can force the HPD pin to be true, the interrupt is still required for proper transition to TXON power mode.

Thank you for your support

Regards,
Francesco

0 Venkat Mandela over 7 years ago in reply to Francesco Valla

TI__Expert 5850 points

Hi Francesco,

I have not been able to look into this issue yet. I need a couple of more days. In the meanwhile, can you please look into the below commits where HPD was added for dra7xx-evm?

95ed943fd25e drm/omap: displays: dra7-evm-encoder-tpd12s015: Support for hot plug detection
85507851066d drm/omap: displays: encoder-tpd12s015: Support for hot plug detection
bda1d36775a8 drm/omap: displays: connector-hdmi: Support for hot plug detection
e4ce34d4485c drm/omap: Support for HDMI hot plug detection

regards,
Venkat

0 Francesco Valla over 7 years ago in reply to Venkat Mandela

Intellectual 570 points

Hi Venkat,

I already forced HPD pin to high. Issues rises at lower level, inside hdmi.c, when dealing with RXDET internal line (of wich I have no details).

In the mean time, I (blindly) adopted the following hack to force the RXDET line, but I'm not sure this is the right path to follow:
paste.ubuntu.com/.../

Can you confirm this is acceptable?

Thank you

Br,
Francesco

0 Mariya Petkova over 7 years ago in reply to Francesco Valla

TI__Expert 4885 points

Hi, Francesco Valla,

The site you gave is blocked in TI office. Can you please download it and share it as a doc file, so Venkat to be able to check it?

Thank you!
Regards,
Mariya

0 Francesco Valla over 7 years ago in reply to Mariya Petkova

Intellectual 570 points

Hi Mariya,
here is the patch.

Br,
Francesco

0001-drm-omap-hdmi-add-Dt-switch-for-forced-cable-detection.patch.txt

From 66d4f8b2edb1d8cf8bc2a2d1559dcd05a99b09a9 Mon Sep 17 00:00:00 2001
From: Francesco Valla <francesco.valla@mta.it>
Date: Mon, 24 Jul 2017 09:51:15 +0200
Subject: [PATCH] drm: omap: hdmi: add DT switch for forced cable detection

Signed-off-by: Francesco Valla <francesco.valla@mta.it>
---
 drivers/gpu/drm/omapdrm/dss/hdmi.h  |  2 ++
 drivers/gpu/drm/omapdrm/dss/hdmi5.c | 10 +++++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/omapdrm/dss/hdmi.h b/drivers/gpu/drm/omapdrm/dss/hdmi.h
index 63e7115..0160ca4 100644
--- a/drivers/gpu/drm/omapdrm/dss/hdmi.h
+++ b/drivers/gpu/drm/omapdrm/dss/hdmi.h
@@ -365,6 +365,8 @@ struct omap_hdmi {
 	spinlock_t audio_playing_lock;
 	bool audio_playing;
 	bool display_enabled;
+
+	bool forced_detection;
 };
 
 #endif
diff --git a/drivers/gpu/drm/omapdrm/dss/hdmi5.c b/drivers/gpu/drm/omapdrm/dss/hdmi5.c
index 5493022..afa28cd 100644
--- a/drivers/gpu/drm/omapdrm/dss/hdmi5.c
+++ b/drivers/gpu/drm/omapdrm/dss/hdmi5.c
@@ -107,7 +107,11 @@ static irqreturn_t hdmi_irq_handler(int irq, void *data)
 
 		hdmi_wp_set_phy_pwr(wp, HDMI_PHYPWRCMD_LDOON);
 
-		REG_FLD_MOD(hdmi.phy.base, HDMI_TXPHY_PAD_CFG_CTRL, 0, 15, 15);
+		/* If HDMI detection has to be forced, force the RXDET line to 1 */
+		if (hdmi.forced_detection)
+			REG_FLD_MOD(hdmi.phy.base, HDMI_TXPHY_PAD_CFG_CTRL, 1, 14, 7);
+		else
+			REG_FLD_MOD(hdmi.phy.base, HDMI_TXPHY_PAD_CFG_CTRL, 0, 15, 15);
 
 	} else if (irqstatus & HDMI_IRQ_LINK_CONNECT) {
 		hdmi_wp_set_phy_pwr(wp, HDMI_PHYPWRCMD_TXON);
@@ -581,6 +585,10 @@ static int hdmi_probe_of(struct platform_device *pdev)
 	struct device_node *ep;
 	int r;
 
+	hdmi.forced_detection = of_property_read_bool(node, "forced-detection");
+	if (hdmi.forced_detection)
+		dev_info(&pdev->dev, "force cable detection.");
+
 	ep = omapdss_of_get_first_endpoint(node);
 	if (!ep)
 		return 0;
-- 
2.7.4

0 Venkat Mandela over 7 years ago in reply to Francesco Valla

TI__Expert 5850 points

Francesco,

The patch seems to be OK. I found an old patch which seems to be doing the same thing but also sets the RXDET_LINE value. I was not able to test this yet.

+ v = hdmi_read_reg(phy->base, HDMI_TXPHY_PAD_CFG_CTRL);
+ v = FLD_MOD(v, 1, 15, 15); /* FORCE_RXDET_HIGH */
+ v = FLD_MOD(v, 0xff, 14, 7); /* RXDET_LINE */
+ hdmi_write_reg(phy->base, HDMI_TXPHY_PAD_CFG_CTRL, v);

regards,
Venkat

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Linux/DRA746: HDMI: cable detection not working when interfacing with DS90UB949