[RFC PATCH v2] irqchip/gic-v3: Add quirk for msm8996 secured registers

[Srinivas Kandagatla]

Access to GICR_WAKER is restricted on msm8996 SoC in Hypervisor.
Its been more than 2 years of wait for this to be fixed, which has
no hopes to be fixed. This change was introduced for the "lead device"
on msm8996 platform. It looks like all publicly available msm8996
devices have this implementation.

So add a quirk to not access this register on msm8996.

With this quirk MSM8996 can at least boot out of mainline,
which can help community to work with boards based on MSM8996.

Without this patch Qualcomm DB820c board reboots when GICR_WAKER
is accessed.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
---
Hi Marc,

There is no errata associated with this quirk, so I could not add
any entries into Documentation/arm64/silicon-errata.txt Or add
any number to the quirk description.

Changes since v1:
- renamed gic_v3 references to gic
- added full mask for iidr register match

thanks,
srini

 drivers/irqchip/irq-gic-v3.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index d5912f1ec884..406d4a44c887 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -41,6 +41,8 @@
 
 #include "irq-gic-common.h"
 
+#define FLAGS_WORKAROUND_GICR_WAKER_MSM8996	(1ULL << 0)
+
 struct redist_region {
 	void __iomem		*redist_base;
 	phys_addr_t		phys_base;
@@ -55,6 +57,7 @@ struct gic_chip_data {
 	struct irq_domain	*domain;
 	u64			redist_stride;
 	u32			nr_redist_regions;
+	u64			flags;
 	bool			has_rss;
 	unsigned int		irq_nr;
 	struct partition_desc	*ppi_descs[16];
@@ -139,6 +142,9 @@ static void gic_enable_redist(bool enable)
 	u32 count = 1000000;	/* 1s! */
 	u32 val;
 
+	if (gic_data.flags & FLAGS_WORKAROUND_GICR_WAKER_MSM8996)
+		return;
+
 	rbase = gic_data_rdist_rd_base();
 
 	val = readl_relaxed(rbase + GICR_WAKER);
@@ -1068,13 +1074,31 @@ static const struct irq_domain_ops partition_domain_ops = {
 	.select = gic_irq_domain_select,
 };
 
+static bool __maybe_unused gic_enable_quirk_msm8996(void *data)
+{
+	struct gic_chip_data *d = data;
+
+	d->flags |= FLAGS_WORKAROUND_GICR_WAKER_MSM8996;
+
+	return true;
+}
+
+static const struct gic_quirk gic_quirks[] = {
+	{
+		.desc	= "GICv3: Qualcomm MSM8996 skip GICR_WAKER Read/Write",
+		.iidr	= 0x00001070,	/* MSM8996 */
+		.mask	= 0xffffffff,
+		.init	= gic_enable_quirk_msm8996,
+	},
+};
+
 static int __init gic_init_bases(void __iomem *dist_base,
 				 struct redist_region *rdist_regs,
 				 u32 nr_redist_regions,
 				 u64 redist_stride,
 				 struct fwnode_handle *handle)
 {
-	u32 typer;
+	u32 typer, iidr;
 	int gic_irqs;
 	int err;
 
@@ -1130,6 +1154,9 @@ static int __init gic_init_bases(void __iomem *dist_base,
 	if (IS_ENABLED(CONFIG_ARM_GIC_V3_ITS) && gic_dist_supports_lpis())
 		its_init(handle, &gic_data.rdists, gic_data.domain);
 
+	iidr = readl_relaxed(dist_base + GICD_IIDR);
+	gic_enable_quirks(iidr, gic_quirks, &gic_data);
+
 	gic_smp_init();
 	gic_dist_init();
 	gic_cpu_init();
-- 
2.18.0