Attachment 145547 Details for Bug 111749 – Patch to add debugfs required for updating TCON

[patch] Patch to add debugfs required for updating TCON

0001-CHROMIUM-drm-add-debugfs-sentinel-file-to-enable-TCO.patch (text/plain), 2.18 KB, created by gaurav.k.singh on 2019-09-27 16:16:38 UTC

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Creator: gaurav.k.singh

Created: 2019-09-27 16:16:38 UTC

Size: 2.18 KB

patch

obsolete

>From 6ad3516b45f2c458d94b43910f136db56b0f037b Mon Sep 17 00:00:00 2001
>From: Gaurav K Singh <gaurav.k.singh@intel.com>
>Date: Thu, 26 Sep 2019 09:03:29 +0530
>Subject: [PATCH] CHROMIUM: drm: add debugfs sentinel file to enable TCON
> firmware updates
>
>The current implementation of drm_dp_dpcd_read uses a double read
>by default, due to issues with certain displays returning garbage
>data on the first read after resuming from sleep. Updating of TCON
>firmware requires specific AUX channel sequencing, and the double
>read breaks this sequence.
>
>The drm_dp_dpcd_read function will check the value of this file,
>and choose either a double or single read based on that value.
>By default the value is set to FALSE. Setting to TRUE will enable
>single read functionality.
>
>BUG=None
>TEST=Pick patch, build, boot, verify file exists & is set to FALSE
>	File: /sys/kernel/debug/dri/dpcd_read_once
>
>Change-Id: I24993f93f70080f38c69fd0674d7062e821cab85
>Signed-off-by: Gaurav K Singh <gaurav.k.singh@intel.com>
>---
> drivers/gpu/drm/drm_drv.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
>diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>index b1f90dcef363..8b87675296f2 100644
>--- a/drivers/gpu/drm/drm_drv.c
>+++ b/drivers/gpu/drm/drm_drv.c
>@@ -964,6 +964,14 @@ static int drm_stub_open(struct inode *inode, struct file *filp)
> /* When set to true, allow set/drop master ioctls as normal user */
> bool drm_master_relax;
> 
>+/*
>+ * When set to true, drm_dp_dpcd_read uses a single read. This
>+ * enables updating of the TCON firmware, which requires a
>+ * specific sequence of read/writes, and does not tolerate a
>+ * double read. Value in file is set to false by default.
>+ */
>+bool dpcd_read_once;
>+
> static const struct file_operations drm_stub_fops = {
> 	.owner = THIS_MODULE,
> 	.open = drm_stub_open,
>@@ -1007,6 +1015,12 @@ static int __init drm_core_init(void)
> 			  "Cannot create /sys/kernel/debug/dri/drm_master_relax\n");
> 	}
> 
>+	if (!debugfs_create_bool("dpcd_read_once", S_IRUSR | S_IWUSR,
>+				drm_debugfs_root, &dpcd_read_once)) {
>+		DRM_ERROR(
>+			"Cannot create /sys/kernel/debug/dri/dpcd_read_once\n");
>+	}
>+
> 	ret = register_chrdev(DRM_MAJOR, "drm", &drm_stub_fops);
> 	if (ret < 0)
> 		goto error;
>-- 
>1.9.1
>

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Attachments on bug 111749: 145431 | 145432 | 145460 | 145489 | 145509 | 145547 | 145548 | 145549

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