From d1ea8bad9b9be93fadaf8c67d6177ecebbe75ff0 Mon Sep 17 00:00:00 2001
From: Bjorn Andersson <bjorn.andersson@linaro.org>
Date: Wed, 20 Apr 2022 21:15:50 -0700
Subject: drm/msm/dpu: Issue MDSS reset during initialization
Git-commit: 3e9c146f4997e32d257215b0036b2425c6053ffe
Patch-mainline: v5.19-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

It's typical for the bootloader to bring up the display for showing a
boot splash or efi framebuffer. But in some cases the kernel driver ends
up only partially configuring (in particular) the DPU, which might
result in e.g. that two different data paths attempts to push data to
the interface - with resulting graphical artifacts.

Naturally the end goal would be to inherit the bootloader's
configuration and provide the user with a glitch free handover from the
boot configuration to a running DPU.

But as implementing seamless transition from the bootloader
configuration to the running OS will be a considerable effort, start by
simply resetting the entire MDSS to its power-on state, to avoid the
partial configuration.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/482796/
Link: https://lore.kernel.org/r/20220421041550.643964-2-bjorn.andersson@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/msm/msm_mdss.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/gpu/drm/msm/msm_mdss.c b/drivers/gpu/drm/msm/msm_mdss.c
index f6f0d0fa5ab2..20f154dda9cf 100644
--- a/drivers/gpu/drm/msm/msm_mdss.c
+++ b/drivers/gpu/drm/msm/msm_mdss.c
@@ -4,11 +4,13 @@
  */
 
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/irq.h>
 #include <linux/irqchip.h>
 #include <linux/irqdesc.h>
 #include <linux/irqchip/chained_irq.h>
 #include <linux/pm_runtime.h>
+#include <linux/reset.h>
 
 #include "msm_drv.h"
 #include "msm_kms.h"
@@ -193,6 +195,32 @@ static void msm_mdss_destroy(struct msm_mdss *msm_mdss)
 	irq_set_chained_handler_and_data(irq, NULL, NULL);
 }
 
+static int msm_mdss_reset(struct device *dev)
+{
+	struct reset_control *reset;
+
+	reset = reset_control_get_optional_exclusive(dev, NULL);
+	if (!reset) {
+		/* Optional reset not specified */
+		return 0;
+	} else if (IS_ERR(reset)) {
+		return dev_err_probe(dev, PTR_ERR(reset),
+				     "failed to acquire mdss reset\n");
+	}
+
+	reset_control_assert(reset);
+	/*
+	 * Tests indicate that reset has to be held for some period of time,
+	 * make it one frame in a typical system
+	 */
+	msleep(20);
+	reset_control_deassert(reset);
+
+	reset_control_put(reset);
+
+	return 0;
+}
+
 /*
  * MDP5 MDSS uses at most three specified clocks.
  */
@@ -229,6 +257,10 @@ static struct msm_mdss *msm_mdss_init(struct platform_device *pdev, bool is_mdp5
 	int ret;
 	int irq;
 
+	ret = msm_mdss_reset(&pdev->dev);
+	if (ret)
+		return ERR_PTR(ret);
+
 	msm_mdss = devm_kzalloc(&pdev->dev, sizeof(*msm_mdss), GFP_KERNEL);
 	if (!msm_mdss)
 		return ERR_PTR(-ENOMEM);
-- 
2.38.1