linux-kernel - [PATCH] input: revert commit 9140ce4 to fix ELAN1206 touchpad issues

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Message-ID: <CAEvyrHnEY-ppdAN8gXPZu89_mqVvQgf3HLm16mF901Qp2kSoaQ@mail.gmail.com>
Date: Wed, 19 Feb 2025 22:23:27 -0800
From: Eliah Reeves <ereeclimb@...il.com>
To: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] input: revert commit 9140ce4 to fix ELAN1206 touchpad issues

From: Eliah Reeves <ereeclimb@...il.com>
>From dd4478d63b6a2b6891fcc1800eb26ce3f1ead1d4 Mon Sep 17 00:00:00 2001
Date: Wed, 19 Feb 2025 20:58:52 -0800
Subject: [PATCH] input: revert commit 9140ce4 to fix ELAN1206 touchpad issues

Reverting commit 9140ce47872bfd89fca888c2f992faa51d20c2bc fixes a
regression that caused touchpad malfunctions. The original change
introduced unintended behavior affecting touchpad input.
---
 drivers/dma/idma64.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/idma64.c b/drivers/dma/idma64.c
index d147353d47ab..afcce6f5a636 100644
--- a/drivers/dma/idma64.c
+++ b/drivers/dma/idma64.c
@@ -171,9 +171,10 @@ static irqreturn_t idma64_irq(int irq, void *dev)
        u32 status_err;
        unsigned short i;

+       /* Commented to restore ELAN1206 Touchpad functionality */
        /* Since IRQ may be shared, check if DMA controller is powered on */
-       if (status == GENMASK(31, 0))
-               return IRQ_NONE;
+       /* if (status == GENMASK(31, 0))
+             return IRQ_NONE; */

        dev_vdbg(idma64->dma.dev, "%s: status=%#x\n", __func__, status);

--
2.48.1

1: Description
===========

Reverting commit 9140ce47872bfd89fca888c2f992faa51d20c2bc fixes a
regression that caused touchpad malfunctions. The original change
introduced unintended behavior affecting touchpad input with the
ELAN1206.

2: Touchpad Behavior with 9140ce47872bfd89fca888c2f992faa51d20c2bc
===========
The touchpad appears to send an event indicating touch up immediately
after each touch down event. This prevents libinput from moving the
cursor rendering the touchpad useless. It is also worth noting that in
addition to incorrect events the touchpad also appears to send events
much less frequently.

evtest output:

  Event: time 1738819278.422243, type 3 (EV_ABS), code 57
(ABS_MT_TRACKING_ID), value 73
  Event: time 1738819278.422243, type 3 (EV_ABS), code 53
(ABS_MT_POSITION_X), value 1264
  Event: time 1738819278.422243, type 3 (EV_ABS), code 54
(ABS_MT_POSITION_Y), value 860
  Event: time 1738819278.422243, type 1 (EV_KEY), code 330 (BTN_TOUCH), value 1
  Event: time 1738819278.422243, type 1 (EV_KEY), code 325
(BTN_TOOL_FINGER), value 1
  Event: time 1738819278.422243, type 3 (EV_ABS), code 0 (ABS_X), value 1264
  Event: time 1738819278.422243, type 3 (EV_ABS), code 1 (ABS_Y), value 860
  Event: time 1738819278.422243, type 4 (EV_MSC), code 5
(MSC_TIMESTAMP), value 0
  Event: time 1738819278.422243, -------------- SYN_REPORT ------------
  Event: time 1738819278.526021, type 3 (EV_ABS), code 57
(ABS_MT_TRACKING_ID), value -1
  Event: time 1738819278.526021, type 1 (EV_KEY), code 330 (BTN_TOUCH), value 0
  Event: time 1738819278.526021, type 1 (EV_KEY), code 325
(BTN_TOOL_FINGER), value 0
  Event: time 1738819278.526021, -------------- SYN_REPORT ------------
  Event: time 1738819278.630874, type 3 (EV_ABS), code 57
(ABS_MT_TRACKING_ID), value 74
  Event: time 1738819278.630874, type 3 (EV_ABS), code 53
(ABS_MT_POSITION_X), value 1415
  Event: time 1738819278.630874, type 3 (EV_ABS), code 54
(ABS_MT_POSITION_Y), value 799

3: Touchpad Behavior without 9140ce47872bfd89fca888c2f992faa51d20c2bc
===========
The touchpad functions smoothly and consistently.

4: Fixes
===========
closes: https://bugzilla.kernel.org/show_bug.cgi?id=219799

5: Impacts
===========
Reverting 9140ce47872bfd89fca888c2f992faa51d20c2bc would theoretically
reopen https://lore.kernel.org/r/700bbb84-90e1-4505-8ff0-3f17ea8bc631@gmail.com

6: Methods
===========
I bisected the Linux kernel and found that
9140ce47872bfd89fca888c2f992faa51d20c2bc was the first commit where my
touchpad didn't work. Building the latest kernel with 9140ce4 removed
resulted in a working touchpad.

Let me know if I can help.
Signed-off-by: Eliah Reeves <ereeclimb@...il.com>