[PATCH 4/4] drm/bridge: dw-hdmi: add cec driver

On 06/02/17 08:43, Jose Abreu wrote:

Hi Hans,


On 02-06-2017 07:31, Hans Verkuil wrote:

quoted

On 06/01/2017 03:47 PM, Neil Armstrong wrote:

quoted

On 05/30/2017 04:23 PM, Russell King wrote:

quoted

Add a CEC driver for the dw-hdmi hardware.

Signed-off-by: Russell King <redacted>
---
  drivers/gpu/drm/bridge/synopsys/Kconfig       |   8 +
  drivers/gpu/drm/bridge/synopsys/Makefile      |   1 +
  drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c | 320
++++++++++++++++++++++++++
  drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.h |  19 ++
  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c     |  40 +++-
  5 files changed, 387 insertions(+), 1 deletion(-)
  create mode 100644
drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c
  create mode 100644
drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.h

diff --git a/drivers/gpu/drm/bridge/synopsys/Kconfig

b/drivers/gpu/drm/bridge/synopsys/Kconfig
index 40d2827a6d19..bd30a0a07272 100644

--- a/drivers/gpu/drm/bridge/synopsys/Kconfig
+++ b/drivers/gpu/drm/bridge/synopsys/Kconfig

@@ -21,3 +21,11 @@ config DRM_DW_HDMI_I2S_AUDIO
      help
        Support the I2S Audio interface which is part of the

Synopsys
        Designware HDMI block.
+
+config DRM_DW_HDMI_CEC
+    tristate "Synopsis Designware CEC interface"
+    depends on DRM_DW_HDMI && MEDIA_CEC_SUPPORT
+    select MEDIA_CEC_NOTIFIER
+    help
+      Support the CE interface which is part of the Synopsis
+      Designware HDMI block.

diff --git a/drivers/gpu/drm/bridge/synopsys/Makefile

b/drivers/gpu/drm/bridge/synopsys/Makefile
index 17aa7a65b57e..6fe415903668 100644

--- a/drivers/gpu/drm/bridge/synopsys/Makefile
+++ b/drivers/gpu/drm/bridge/synopsys/Makefile

@@ -3,3 +3,4 @@
  obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
  obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
  obj-$(CONFIG_DRM_DW_HDMI_I2S_AUDIO) += dw-hdmi-i2s-audio.o
+obj-$(CONFIG_DRM_DW_HDMI_CEC) += dw-hdmi-cec.o

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c

b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c
new file mode 100644
index 000000000000..761ef5ae687d

--- /dev/null
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c

@@ -0,0 +1,320 @@
+/*
+ * Designware HDMI CEC driver
+ *
+ * Copyright (C) 2015-2017 Russell King.
+ *
+ * This program is free software; you can redistribute it

and/or modify
+ * it under the terms of the GNU General Public License
version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include <drm/drm_edid.h>
+
+#include <media/cec.h>
+#include <media/cec-notifier.h>
+
+#include "dw-hdmi-cec.h"
+
+enum {
+    HDMI_IH_CEC_STAT0    = 0x0106,
+    HDMI_IH_MUTE_CEC_STAT0    = 0x0186,
+
+    HDMI_CEC_CTRL        = 0x7d00,
+    CEC_CTRL_START        = BIT(0),
+    CEC_CTRL_NORMAL        = 1 << 1,
+
+    HDMI_CEC_STAT        = 0x7d01,
+    CEC_STAT_DONE        = BIT(0),
+    CEC_STAT_EOM        = BIT(1),
+    CEC_STAT_NACK        = BIT(2),
+    CEC_STAT_ARBLOST    = BIT(3),
+    CEC_STAT_ERROR_INIT    = BIT(4),
+    CEC_STAT_ERROR_FOLL    = BIT(5),
+    CEC_STAT_WAKEUP        = BIT(6),

I hadn't realized until Jose Abreu's latest reply, but you need
to check the
ARBLOST status and set the TX state to CEC_TX_STATUS_ARB_LOST.

I think CEC_STAT_ERROR_FOLL might equal
CEC_TX_STATUS_LOW_DRIVE, but without
documentation I can't be sure.

My experience is that this low drive condition tends to be
poorly reported by
hardware. Either that or poorly documented. This is why I added a
CEC_TX_STATUS_ERROR status as a catch-all error status when it
is unclear from
the hardware/documentation what error occurred.

Jose, do you know which status bit is used to report a follower
pulling the
CEC line low for a long time (approx. 3.6 ms) to signal a CEC
error?

Bit 5 for follower error, bit 4 for initiator error.

I gathered that from the define names :-)

But what does it mean? What sort of error is reported here?

I'm guessing here that "follower error" means that one of the remote
CEC devices forced a Low Drive condition, where "initiator error"
means that our adapter forced a Low Drive condition on the bus.

Would that be correct?

If so, then the CEC_STAT_ERROR_INIT can be ignored and ERROR_FOLL
maps to the LOW_DRIVE status.

(Low Drive condition is what is described in section CEC 7.4 "CEC Line
Error Handling" of the HDMI 1.4 Specification).

Regards,

	Hans