soc: qcom-geni-se: Add interconnect support to fix earlycon crash

QUP core clock is shared among all the SE drivers present on particular
QUP wrapper, the system will reset(unclocked access) if earlycon used after
QUP core clock is put to 0 from other SE drivers before real console comes
up.

As earlycon can't vote for it's QUP core need, to fix this add ICC
support to common/QUP wrapper driver and put vote for QUP core from
probe on behalf of earlycon and remove vote during earlycon exit call.

Signed-off-by: Akash Asthana <akashast@codeaurora.org>
Reported-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Link: https://lore.kernel.org/r/1592908737-7068-3-git-send-email-akashast@codeaurora.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/soc/qcom/qcom-geni-se.c

@@ -3,6 +3,7 @@
 
 #include <linux/acpi.h>
 #include <linux/clk.h>
+#include <linux/console.h>
 #include <linux/slab.h>
 #include <linux/dma-mapping.h>
 #include <linux/io.h>
@@ -90,11 +91,14 @@ struct geni_wrapper {
 	struct device *dev;
 	void __iomem *base;
 	struct clk_bulk_data ahb_clks[NUM_AHB_CLKS];
+	struct geni_icc_path to_core;
 };
 
 static const char * const icc_path_names[] = {"qup-core", "qup-config",
 						"qup-memory"};
 
+static struct geni_wrapper *earlycon_wrapper;
+
 #define QUP_HW_VER_REG			0x4
 
 /* Common SE registers */
@@ -802,11 +806,38 @@ int geni_icc_disable(struct geni_se *se)
 }
 EXPORT_SYMBOL(geni_icc_disable);
 
+void geni_remove_earlycon_icc_vote(void)
+{
+	struct geni_wrapper *wrapper;
+	struct device_node *parent;
+	struct device_node *child;
+
+	if (!earlycon_wrapper)
+		return;
+
+	wrapper = earlycon_wrapper;
+	parent = of_get_next_parent(wrapper->dev->of_node);
+	for_each_child_of_node(parent, child) {
+		if (!of_device_is_compatible(child, "qcom,geni-se-qup"))
+			continue;
+		wrapper = platform_get_drvdata(of_find_device_by_node(child));
+		icc_put(wrapper->to_core.path);
+		wrapper->to_core.path = NULL;
+
+	}
+	of_node_put(parent);
+
+	earlycon_wrapper = NULL;
+}
+EXPORT_SYMBOL(geni_remove_earlycon_icc_vote);
+
 static int geni_se_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct resource *res;
 	struct geni_wrapper *wrapper;
+	struct console __maybe_unused *bcon;
+	bool __maybe_unused has_earlycon = false;
 	int ret;
 
 	wrapper = devm_kzalloc(dev, sizeof(*wrapper), GFP_KERNEL);
@@ -829,6 +860,43 @@ static int geni_se_probe(struct platform_device *pdev)
 		}
 	}
 
+#ifdef CONFIG_SERIAL_EARLYCON
+	for_each_console(bcon) {
+		if (!strcmp(bcon->name, "qcom_geni")) {
+			has_earlycon = true;
+			break;
+		}
+	}
+	if (!has_earlycon)
+		goto exit;
+
+	wrapper->to_core.path = devm_of_icc_get(dev, "qup-core");
+	if (IS_ERR(wrapper->to_core.path))
+		return PTR_ERR(wrapper->to_core.path);
+	/*
+	 * Put minmal BW request on core clocks on behalf of early console.
+	 * The vote will be removed earlycon exit function.
+	 *
+	 * Note: We are putting vote on each QUP wrapper instead only to which
+	 * earlycon is connected because QUP core clock of different wrapper
+	 * share same voltage domain. If core1 is put to 0, then core2 will
+	 * also run at 0, if not voted. Default ICC vote will be removed ASA
+	 * we touch any of the core clock.
+	 * core1 = core2 = max(core1, core2)
+	 */
+	ret = icc_set_bw(wrapper->to_core.path, GENI_DEFAULT_BW,
+				GENI_DEFAULT_BW);
+	if (ret) {
+		dev_err(&pdev->dev, "%s: ICC BW voting failed for core: %d\n",
+			__func__, ret);
+		return ret;
+	}
+
+	if (of_get_compatible_child(pdev->dev.of_node, "qcom,geni-debug-uart"))
+		earlycon_wrapper = wrapper;
+	of_node_put(pdev->dev.of_node);
+#endif
+exit:
 	dev_set_drvdata(dev, wrapper);
 	dev_dbg(dev, "GENI SE Driver probed\n");
 	return devm_of_platform_populate(dev);

drivers/tty/serial/qcom_geni_serial.c

@@ -1121,6 +1121,12 @@ static inline void qcom_geni_serial_enable_early_read(struct geni_se *se,
 						      struct console *con) { }
 #endif
 
+static int qcom_geni_serial_earlycon_exit(struct console *con)
+{
+	geni_remove_earlycon_icc_vote();
+	return 0;
+}
+
 static int __init qcom_geni_serial_earlycon_setup(struct earlycon_device *dev,
 								const char *opt)
 {
@@ -1166,6 +1172,7 @@ static int __init qcom_geni_serial_earlycon_setup(struct earlycon_device *dev,
 	writel(stop_bit_len, uport->membase + SE_UART_TX_STOP_BIT_LEN);
 
 	dev->con->write = qcom_geni_serial_earlycon_write;
+	dev->con->exit = qcom_geni_serial_earlycon_exit;
 	dev->con->setup = NULL;
 	qcom_geni_serial_enable_early_read(&se, dev->con);
 

include/linux/qcom-geni-se.h

@@ -454,5 +454,7 @@ int geni_icc_set_bw(struct geni_se *se);
 int geni_icc_enable(struct geni_se *se);
 
 int geni_icc_disable(struct geni_se *se);
+
+void geni_remove_earlycon_icc_vote(void);
 #endif
 #endif