[PATCH 2/2] soundwire: intel_auxdevice: Don't disable IRQs before removing children

[Charles Keepax <ckeepax@opensource.cirrus.com>]

Currently the auxiliary device for the link disables IRQs before
it calls sdw_bus_master_delete(). This has the side effect that
none of the devices on the link can access their own registers
whilst their remove functions run, because the IRQs are required
for bus transactions to function.

It would appear the reason for the disabling of the IRQs is that
the IRQ handler iterates through a linked list of all the links,
once a link is removed the memory pointed at by this linked list
is freed, but not removed from the linked_list. Add a list_del()
for the linked list item, note whilst the list itself is contained
in the intel_init portion of the code, the list remove needs
to be attached to the auxiliary device for the link, since
that owns the memory that the list points at. Locking is also
required to ensure the IRQ handler runs either before or after
any additions/removals from the list.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
---
 drivers/soundwire/intel.h           |  1 +
 drivers/soundwire/intel_auxdevice.c |  5 ++++-
 drivers/soundwire/intel_init.c      | 16 ++++++++++++++++
 include/linux/soundwire/sdw_intel.h |  1 +
 4 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/soundwire/intel.h b/drivers/soundwire/intel.h
index 7a2e7e73ad632..ec82ac8d54adb 100644
--- a/drivers/soundwire/intel.h
+++ b/drivers/soundwire/intel.h
@@ -47,6 +47,7 @@ struct sdw_intel_link_res {
 	u32 link_mask;
 	struct sdw_cdns *cdns;
 	struct list_head list;
+	struct mutex *link_lock; /* lock protecting list */
 	struct hdac_bus *hbus;
 };
 
diff --git a/drivers/soundwire/intel_auxdevice.c b/drivers/soundwire/intel_auxdevice.c
index 901a71262094f..1743793de2bd0 100644
--- a/drivers/soundwire/intel_auxdevice.c
+++ b/drivers/soundwire/intel_auxdevice.c
@@ -508,9 +508,12 @@ static void intel_link_remove(struct auxiliary_device *auxdev)
 	if (!bus->prop.hw_disabled) {
 		sdw_intel_debugfs_exit(sdw);
 		cancel_delayed_work_sync(&cdns->attach_dwork);
-		sdw_cdns_enable_interrupt(cdns, false);
 	}
+
 	sdw_bus_master_delete(bus);
+
+	if (!bus->prop.hw_disabled)
+		sdw_cdns_enable_interrupt(cdns, false);
 }
 
 int intel_link_process_wakeen_event(struct auxiliary_device *auxdev)
diff --git a/drivers/soundwire/intel_init.c b/drivers/soundwire/intel_init.c
index ad48d67fa9358..117c2e42b9bac 100644
--- a/drivers/soundwire/intel_init.c
+++ b/drivers/soundwire/intel_init.c
@@ -28,6 +28,15 @@ static void intel_link_dev_release(struct device *dev)
 	kfree(ldev);
 }
 
+static void intel_link_list_del(void *data)
+{
+	struct sdw_intel_link_res *link = data;
+
+	mutex_lock(link->link_lock);
+	list_del(&link->list);
+	mutex_unlock(link->link_lock);
+}
+
 /* alloc, init and add link devices */
 static struct sdw_intel_link_dev *intel_link_dev_register(struct sdw_intel_res *res,
 							  struct sdw_intel_ctx *ctx,
@@ -79,6 +88,7 @@ static struct sdw_intel_link_dev *intel_link_dev_register(struct sdw_intel_res *
 		link->shim_lock = res->eml_lock;
 		link->mic_privacy = res->mic_privacy;
 	}
+	link->link_lock = &ctx->link_lock;
 
 	link->ops = res->ops;
 	link->dev = res->dev;
@@ -145,8 +155,10 @@ irqreturn_t sdw_intel_thread(int irq, void *dev_id)
 	struct sdw_intel_ctx *ctx = dev_id;
 	struct sdw_intel_link_res *link;
 
+	mutex_lock(&ctx->link_lock);
 	list_for_each_entry(link, &ctx->link_list, list)
 		sdw_cdns_irq(irq, link->cdns);
+	mutex_unlock(&ctx->link_lock);
 
 	return IRQ_HANDLED;
 }
@@ -210,6 +222,7 @@ static struct sdw_intel_ctx
 	ctx->link_mask = res->link_mask;
 	ctx->handle = res->handle;
 	mutex_init(&ctx->shim_lock);
+	mutex_init(&ctx->link_lock);
 
 	link_mask = ctx->link_mask;
 
@@ -246,7 +259,10 @@ static struct sdw_intel_ctx
 			i++;
 			goto err;
 		}
+		mutex_lock(&ctx->link_lock);
 		list_add_tail(&link->list, &ctx->link_list);
+		mutex_unlock(&ctx->link_lock);
+		devm_add_action_or_reset(&ldev->auxdev.dev, intel_link_list_del, link);
 		bus = &link->cdns->bus;
 		/* Calculate number of slaves */
 		list_for_each(node, &bus->slaves)
diff --git a/include/linux/soundwire/sdw_intel.h b/include/linux/soundwire/sdw_intel.h
index 9710f2dc04e29..7495d35ed2fc3 100644
--- a/include/linux/soundwire/sdw_intel.h
+++ b/include/linux/soundwire/sdw_intel.h
@@ -307,6 +307,7 @@ struct sdw_intel_ctx {
 	acpi_handle handle;
 	struct sdw_intel_link_dev **ldev;
 	struct list_head link_list;
+	struct mutex link_lock; /* lock protecting link_list */
 	struct mutex shim_lock; /* lock for access to shared SHIM registers */
 	u32 shim_mask;
 	u32 shim_base;
-- 
2.47.3