From eb58f9f6c23a7cd1c1f96e69a5692276e3541fd1 Mon Sep 17 00:00:00 2001
From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Date: Wed, 17 Jul 2024 11:11:12 +0200
Subject: [PATCH] soundwire: intel: add probe-time check on link id

In older platforms, the number of links was constant and hard-coded to
4. Newer platforms can have varying number of links, so we need to add
a probe-time check to make sure the ACPI-reported information with
_DSD properties is aligned with hardware capabilities reported in the
SoundWire LCAP register.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
 drivers/soundwire/intel.h           |  7 +++++++
 drivers/soundwire/intel_ace2x.c     | 20 ++++++++++++++++++++
 drivers/soundwire/intel_auxdevice.c | 14 ++++++++++++++
 include/linux/soundwire/sdw_intel.h |  3 +++
 4 files changed, 44 insertions(+)

diff --git a/drivers/soundwire/intel.h b/drivers/soundwire/intel.h
index f4235f5991c37d..dddd293814418b 100644
--- a/drivers/soundwire/intel.h
+++ b/drivers/soundwire/intel.h
@@ -224,6 +224,13 @@ static inline bool sdw_intel_sync_check_cmdsync_unlocked(struct sdw_intel *sdw)
 	return false;
 }
 
+static inline int sdw_intel_get_link_count(struct sdw_intel *sdw)
+{
+	if (SDW_INTEL_CHECK_OPS(sdw, get_link_count))
+		return SDW_INTEL_OPS(sdw, get_link_count)(sdw);
+	return 4; /* default on older generations */
+}
+
 /* common bus management */
 int intel_start_bus(struct sdw_intel *sdw);
 int intel_start_bus_after_reset(struct sdw_intel *sdw);
diff --git a/drivers/soundwire/intel_ace2x.c b/drivers/soundwire/intel_ace2x.c
index a473d4e35604d4..3084f0ac7159e3 100644
--- a/drivers/soundwire/intel_ace2x.c
+++ b/drivers/soundwire/intel_ace2x.c
@@ -713,10 +713,30 @@ static void intel_program_sdi(struct sdw_intel *sdw, int dev_num)
 			__func__, sdw->instance, dev_num);
 }
 
+static int intel_get_link_count(struct sdw_intel *sdw)
+{
+	int ret;
+
+	ret = hdac_bus_eml_get_count(sdw->link_res->hbus, true, AZX_REG_ML_LEPTR_ID_SDW);
+	if (!ret) {
+		dev_err(sdw->cdns.dev, "%s: could not retrieve link count\n", __func__);
+		return -ENODEV;
+	}
+
+	if (ret > SDW_INTEL_MAX_LINKS) {
+		dev_err(sdw->cdns.dev, "%s: link count %d exceed max %d\n", __func__, ret, SDW_INTEL_MAX_LINKS);
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
 const struct sdw_intel_hw_ops sdw_intel_lnl_hw_ops = {
 	.debugfs_init = intel_ace2x_debugfs_init,
 	.debugfs_exit = intel_ace2x_debugfs_exit,
 
+	.get_link_count = intel_get_link_count,
+
 	.register_dai = intel_register_dai,
 
 	.check_clock_stop = intel_check_clock_stop,
diff --git a/drivers/soundwire/intel_auxdevice.c b/drivers/soundwire/intel_auxdevice.c
index e372195b07b30d..599954d9275299 100644
--- a/drivers/soundwire/intel_auxdevice.c
+++ b/drivers/soundwire/intel_auxdevice.c
@@ -325,6 +325,20 @@ static int intel_link_probe(struct auxiliary_device *auxdev,
 	bus->link_id = auxdev->id;
 	bus->clk_stop_timeout = 1;
 
+	/*
+	 * paranoia check: make sure ACPI-reported number of links is aligned with
+	 * hardware capabilities.
+	 */
+	ret = sdw_intel_get_link_count(sdw);
+	if (ret < 0) {
+		dev_err(dev, "%s: sdw_intel_get_link_count failed: %d\n", __func__, ret);
+		return ret;
+	}
+	if (ret <= sdw->instance) {
+		dev_err(dev, "%s: invalid link id %d, link count %d\n", __func__, auxdev->id, ret);
+		return -EINVAL;
+	}
+
 	sdw_cdns_probe(cdns);
 
 	/* Set ops */
diff --git a/include/linux/soundwire/sdw_intel.h b/include/linux/soundwire/sdw_intel.h
index edbe1d4af8f85d..37ae69365fe263 100644
--- a/include/linux/soundwire/sdw_intel.h
+++ b/include/linux/soundwire/sdw_intel.h
@@ -388,6 +388,7 @@ struct sdw_intel;
 /* struct intel_sdw_hw_ops - SoundWire ops for Intel platforms.
  * @debugfs_init: initialize all debugfs capabilities
  * @debugfs_exit: close and cleanup debugfs capabilities
+ * @get_link_count: fetch link count from hardware registers
  * @register_dai: read all PDI information and register DAIs
  * @check_clock_stop: throw error message if clock is not stopped.
  * @start_bus: normal start
@@ -412,6 +413,8 @@ struct sdw_intel_hw_ops {
 	void (*debugfs_init)(struct sdw_intel *sdw);
 	void (*debugfs_exit)(struct sdw_intel *sdw);
 
+	int (*get_link_count)(struct sdw_intel *sdw);
+
 	int (*register_dai)(struct sdw_intel *sdw);
 
 	void (*check_clock_stop)(struct sdw_intel *sdw);