oxnas: backport patch fixing hang after reboot

Sungbo Eo <mans0n@gorani.run> posted a patch fixing the long-standing
reboot problem on the OXNAS OX820 platform:
  irqchip/versatile-fpga: Handle chained IRQs properly

It got queued for 5.7. Import it to oxnas target patches for now.

Fixes: b4917fa907 ("oxnas: fix oxnas-rps-timer dt-match")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>

target/linux/oxnas/patches-5.4/001-irqchip-versatile-fpga-Handle-chained-IRQs-properly.patch

@@ -0,0 +1,77 @@
+From patchwork Thu Mar 19 02:34:48 2020
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 7bit
+X-Patchwork-Submitter: Sungbo Eo <mans0n@gorani.run>
+X-Patchwork-Id: 11446405
+From: Sungbo Eo <mans0n@gorani.run>
+To: Linus Walleij <linus.walleij@linaro.org>,
+ Thomas Gleixner <tglx@linutronix.de>, Jason Cooper <jason@lakedaemon.net>,
+ Marc Zyngier <maz@kernel.org>, linux-arm-kernel@lists.infradead.org,
+ linux-kernel@vger.kernel.org, linux-oxnas@groups.io
+Subject: [PATCH v2] irqchip/versatile-fpga: Handle chained IRQs properly
+Date: Thu, 19 Mar 2020 11:34:48 +0900
+Message-Id: <20200319023448.1479701-1-mans0n@gorani.run>
+In-Reply-To: <002b72cab9896fa5ac76a52e0cb503ff@kernel.org>
+References: <002b72cab9896fa5ac76a52e0cb503ff@kernel.org>
+MIME-Version: 1.0
+List-Id: <linux-arm-kernel.lists.infradead.org>
+Cc: Sungbo Eo <mans0n@gorani.run>, Neil Armstrong <narmstrong@baylibre.com>
+Sender: "linux-arm-kernel" <linux-arm-kernel-bounces@lists.infradead.org>
+
+Enclose the chained handler with chained_irq_{enter,exit}(), so that the
+muxed interrupts get properly acked.
+
+This patch also fixes a reboot bug on OX820 SoC, where the jiffies timer
+interrupt is never acked. The kernel waits a clock tick forever in
+calibrate_delay_converge(), which leads to a boot hang.
+
+Fixes: c41b16f8c9d9 ("ARM: integrator/versatile: consolidate FPGA IRQ handling code")
+Signed-off-by: Sungbo Eo <mans0n@gorani.run>
+Cc: Neil Armstrong <narmstrong@baylibre.com>
+---
+v2: moved readl below chained_irq_enter()
+    added Fixes tag
+
+ drivers/irqchip/irq-versatile-fpga.c | 12 ++++++++++--
+ 1 file changed, 10 insertions(+), 2 deletions(-)
+
+--- a/drivers/irqchip/irq-versatile-fpga.c
++++ b/drivers/irqchip/irq-versatile-fpga.c
+@@ -6,6 +6,7 @@
+ #include <linux/irq.h>
+ #include <linux/io.h>
+ #include <linux/irqchip.h>
++#include <linux/irqchip/chained_irq.h>
+ #include <linux/irqchip/versatile-fpga.h>
+ #include <linux/irqdomain.h>
+ #include <linux/module.h>
+@@ -68,12 +69,16 @@ static void fpga_irq_unmask(struct irq_d
+ 
+ static void fpga_irq_handle(struct irq_desc *desc)
+ {
++	struct irq_chip *chip = irq_desc_get_chip(desc);
+ 	struct fpga_irq_data *f = irq_desc_get_handler_data(desc);
+-	u32 status = readl(f->base + IRQ_STATUS);
++	u32 status;
+ 
++	chained_irq_enter(chip, desc);
++
++	status = readl(f->base + IRQ_STATUS);
+ 	if (status == 0) {
+ 		do_bad_IRQ(desc);
+-		return;
++		goto out;
+ 	}
+ 
+ 	do {
+@@ -82,6 +87,9 @@ static void fpga_irq_handle(struct irq_d
+ 		status &= ~(1 << irq);
+ 		generic_handle_irq(irq_find_mapping(f->domain, irq));
+ 	} while (status);
++
++out:
++	chained_irq_exit(chip, desc);
+ }
+ 
+ /*