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

commit 1b15483deb3f ("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>

1 files changed, 17 insertions, 10 deletions

diff --git a/drivers/serial/serial_msm_geni.c b/drivers/serial/serial_msm_geni.c
index b8bc61451a0..0e52e32ddf3 100644
--- a/drivers/serial/serial_msm_geni.c
+++ b/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)
-		return;
+	if (!ofnode_device_is_compatible(parent_node, "qcom,geni-se-qup")) {
+		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,
-			&geni_se_version, sizeof(geni_se_version));
-	if (ret != sizeof(geni_se_version))
-		return;
+	/* Read the HW_VER register relative to the parents address space */
+	addr = ofnode_get_addr(parent_node);
+	geni_se_version = readl(addr + QUP_HW_VER_REG);
 
 	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)