video: tegra20: implement a minimal HOST1X driver for essential clock and reset setup

Introduce a simplified HOST1X driver, limited to the basic clock and reset
initialization of the bus.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>

drivers/video/tegra20/Kconfig

@@ -1,6 +1,11 @@
+config HOST1X_TEGRA
+	bool "NVIDIA Tegra host1x BUS support"
+	depends on SIMPLE_BUS
+
 config VIDEO_TEGRA20
 	bool "Enable Display Controller support on Tegra20 and Tegra 30"
 	depends on OF_CONTROL
+	select HOST1X_TEGRA
 	help
 	   T20/T30 support video output to an attached LCD panel as well as
 	   other options such as HDMI. Only the LCD is supported in U-Boot.

drivers/video/tegra20/Makefile

@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0+
 
+obj-$(CONFIG_HOST1X_TEGRA) += tegra-host1x.o
 obj-$(CONFIG_VIDEO_TEGRA20) += tegra-dc.o
 obj-$(CONFIG_VIDEO_DSI_TEGRA30) += tegra-dsi.o tegra-mipi.o mipi-phy.o
 obj-$(CONFIG_TEGRA_BACKLIGHT_PWM) += tegra-pwm-backlight.o

drivers/video/tegra20/tegra-dc.c

@@ -319,11 +319,6 @@ static int tegra_display_probe(struct tegra_lcd_priv *priv,
 						/ priv->pixel_clock) - 2;
 	log_debug("Display clock %lu, divider %lu\n", rate, priv->scdiv);
 
-	/*
-	 * HOST1X is init by default at 150MHz with PLLC as parent
-	 */
-	clock_start_periph_pll(PERIPH_ID_HOST1X, CLOCK_ID_CGENERAL,
-			       150 * 1000000);
 	clock_start_periph_pll(priv->clk->id, priv->clk_parent->id,
 			       rate);
 

drivers/video/tegra20/tegra-host1x.c

@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2025 Svyatoslav Ryhel <clamor95@gmail.com>
+ */
+
+#include <dm.h>
+#include <clk.h>
+#include <log.h>
+#include <reset.h>
+#include <linux/delay.h>
+
+#include <asm/arch/clock.h>
+#include <asm/arch-tegra/clk_rst.h>
+
+struct tegra_host1x_info {
+	u32 clk_parent;
+	u32 rate;
+};
+
+static int tegra_host1x_probe(struct udevice *dev)
+{
+	struct clk *clk;
+	struct reset_ctl reset_ctl;
+	const struct tegra_host1x_info *info;
+	int ret;
+
+	clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(clk)) {
+		log_debug("%s: cannot get HOST1X clock: %ld\n",
+			  __func__, PTR_ERR(clk));
+		return PTR_ERR(clk);
+	}
+
+	ret = reset_get_by_name(dev, "host1x", &reset_ctl);
+	if (ret) {
+		log_debug("%s: cannot get HOST1X reset: %d\n",
+			  __func__, ret);
+		return ret;
+	}
+
+	info = (struct tegra_host1x_info *)dev_get_driver_data(dev);
+
+	reset_assert(&reset_ctl);
+	clock_start_periph_pll(clk->id, info->clk_parent, info->rate);
+
+	mdelay(2);
+	reset_deassert(&reset_ctl);
+
+	return 0;
+}
+
+static const struct tegra_host1x_info tegra20_host1x_info = {
+	.clk_parent = CLOCK_ID_CGENERAL,
+	.rate = 150000000, /* 150 MHz */
+};
+
+static const struct tegra_host1x_info tegra114_host1x_info = {
+	.clk_parent = CLOCK_ID_PERIPH,
+	.rate = 136000000, /* 136 MHz */
+};
+
+static const struct udevice_id tegra_host1x_ids[] = {
+	{
+		.compatible = "nvidia,tegra20-host1x",
+		.data = (ulong)&tegra20_host1x_info
+	}, {
+		.compatible = "nvidia,tegra30-host1x",
+		.data = (ulong)&tegra20_host1x_info
+	}, {
+		.compatible = "nvidia,tegra114-host1x",
+		.data = (ulong)&tegra114_host1x_info
+	}, {
+		.compatible = "nvidia,tegra124-host1x",
+		.data = (ulong)&tegra114_host1x_info
+	}, {
+		/* sentinel */
+	}
+};
+
+U_BOOT_DRIVER(tegra_host1x) = {
+	.name		= "tegra_host1x",
+	.id		= UCLASS_SIMPLE_BUS,
+	.of_match	= tegra_host1x_ids,
+	.probe		= tegra_host1x_probe,
+	.flags		= DM_FLAG_PRE_RELOC,
+};