serial: msm-geni: don't rely on parent misc device

commit 1b15483deb ("misc: add Qualcomm GENI SE QUP device driver")
introduced support for platform-specific oversampling values, necessary
to configure the UART clocks on all platforms at runtime. However it
relies in probing a parent device. Despite the DM_FLAG_PRE_RELOC flag,
this is not done consistently during boot.

Instead, take another approach by relying on ofnode_ helpers to read the
serial engine base address and do the read directly. This fixes early
UART on boards with a non-default oversampling rate.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>

drivers/misc/Kconfig

@@ -527,13 +527,6 @@ config WINBOND_W83627
 	  legacy UART or other devices in the Winbond Super IO chips
 	  on X86 platforms.
 
-config QCOM_GENI_SE
-	bool "Qualcomm GENI Serial Engine Driver"
-	depends on ARCH_SNAPDRAGON
-	help
-	  The driver manages Generic Interface (GENI) firmware based
-	  Qualcomm Technologies, Inc. Universal Peripheral (QUP) Wrapper.
-
 config QFW
 	bool
 	help

drivers/misc/Makefile

@@ -60,7 +60,6 @@ obj-$(CONFIG_NUVOTON_NCT6102D) += nuvoton_nct6102d.o
 obj-$(CONFIG_P2SB) += p2sb-uclass.o
 obj-$(CONFIG_PCA9551_LED) += pca9551_led.o
 obj-$(CONFIG_$(SPL_)PWRSEQ) += pwrseq-uclass.o
-obj-$(CONFIG_QCOM_GENI_SE) += qcom-geni-se.o
 ifdef CONFIG_QFW
 obj-y += qfw.o
 obj-$(CONFIG_QFW_ACPI) += qfw_acpi.o

drivers/misc/qcom-geni-se.c

@@ -1,41 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0+
-/*
- * Qualcomm Generic Interface (GENI) Serial Engine (SE) Wrapper
- *
- * Copyright (C) 2023 Linaro Ltd. <vladimir.zapolskiy@linaro.org>
- */
-
-#include <common.h>
-#include <dm.h>
-#include <misc.h>
-#include <asm/io.h>
-
-static int geni_se_qup_read(struct udevice *dev, int offset,
-			    void *buf, int size)
-{
-	fdt_addr_t base = dev_read_addr(dev);
-
-	if (size != sizeof(u32))
-		return -EINVAL;
-
-	*(u32 *)buf = readl(base + offset);
-
-	return size;
-}
-
-static struct misc_ops geni_se_qup_ops = {
-	.read = geni_se_qup_read,
-};
-
-static const struct udevice_id geni_se_qup_ids[] = {
-	{ .compatible = "qcom,geni-se-qup" },
-	{}
-};
-
-U_BOOT_DRIVER(geni_se_qup) = {
-	.name = "geni_se_qup",
-	.id = UCLASS_MISC,
-	.of_match = geni_se_qup_ids,
-	.ops = &geni_se_qup_ops,
-	.flags  = DM_FLAG_PRE_RELOC,
-};

drivers/serial/Kconfig

@@ -972,8 +972,6 @@ config MSM_SERIAL
 
 config MSM_GENI_SERIAL
 	bool "Qualcomm on-chip GENI UART"
-	select MISC
-	imply QCOM_GENI_SE
 	help
 	  Support UART based on Generic Interface (GENI) Serial Engine (SE),
 	  used on Qualcomm Snapdragon SoCs. Should support all qualcomm SOCs

drivers/serial/serial_msm_geni.c

@@ -485,12 +485,12 @@ static const struct dm_serial_ops msm_serial_ops = {
 	.setbrg = msm_serial_setbrg,
 };
 
-static void geni_set_oversampling(struct udevice *dev)
+static int geni_set_oversampling(struct udevice *dev)
 {
 	struct msm_serial_data *priv = dev_get_priv(dev);
-	struct udevice *parent_dev = dev_get_parent(dev);
+	ofnode parent_node = ofnode_get_parent(dev_ofnode(dev));
 	u32 geni_se_version;
-	int ret;
+	fdt_addr_t addr;
 
 	priv->oversampling = UART_OVERSAMPLING;
 
@@ -498,16 +498,20 @@ static void geni_set_oversampling(struct udevice *dev)
 	 * It could happen that GENI SE IP is missing in the board's device
 	 * tree or GENI UART node is a direct child of SoC device tree node.
 	 */
-	if (device_get_uclass_id(parent_dev) != UCLASS_MISC)
+	if (!ofnode_device_is_compatible(parent_node, "qcom,geni-se-qup")) {
-		return;
+		pr_err("%s: UART node must be a child of geniqup node\n",
+		       __func__);
+		return -ENODEV;
+	}
 
-	ret = misc_read(parent_dev, QUP_HW_VER_REG,
+	/* Read the HW_VER register relative to the parents address space */
-			&geni_se_version, sizeof(geni_se_version));
+	addr = ofnode_get_addr(parent_node);
-	if (ret != sizeof(geni_se_version))
+	geni_se_version = readl(addr + QUP_HW_VER_REG);
-		return;
 
 	if (geni_se_version >= QUP_SE_VERSION_2_5)
 		priv->oversampling /= 2;
+
+	return 0;
 }
 
 static inline void geni_serial_init(struct udevice *dev)
@@ -552,8 +556,11 @@ static inline void geni_serial_init(struct udevice *dev)
 static int msm_serial_probe(struct udevice *dev)
 {
 	struct msm_serial_data *priv = dev_get_priv(dev);
+	int ret;
 
-	geni_set_oversampling(dev);
+	ret = geni_set_oversampling(dev);
+	if (ret < 0)
+		return ret;
 
 	/* No need to reinitialize the UART after relocation */
 	if (gd->flags & GD_FLG_RELOC)