[alsa-devel] [RFC PATCH 29/40] soundwire: intel_init: add kernel module parameter to filter out links

[Pierre-Louis Bossart]

The hardware and ACPI info may report the presence of links that are
not physically enabled (e.g. due to pin-muxing or hardware reworks),
which in turn can result in errors being thrown. This shouldn't be the
case for production devices but will happen a lot on development
devices - even more so when they expose a connector.

Add a module parameter to filter out such links, e.g. adding the
following config to a file in /etc/modprobe.d will select the second
and third links only.

options soundwire_intel_init sdw_link_mask=0x6

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 drivers/soundwire/intel_init.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/soundwire/intel_init.c b/drivers/soundwire/intel_init.c
index 70637a0383d2..6ae8bb13f907 100644
--- a/drivers/soundwire/intel_init.c
+++ b/drivers/soundwire/intel_init.c
@@ -22,6 +22,10 @@
 #define SDW_LINK_BASE		0x30000
 #define SDW_LINK_SIZE		0x10000
 
+static int link_mask;
+module_param_named(sdw_link_mask, link_mask, int, 0444);
+MODULE_PARM_DESC(sdw_link_mask, "Intel link mask (one bit per link)");
+
 struct sdw_link_data {
 	struct sdw_intel_link_res res;
 	struct platform_device *pdev;
@@ -83,6 +87,9 @@ static struct sdw_intel_ctx
 	caps = ioread32(res->mmio_base + SDW_SHIM_BASE + SDW_SHIM_LCAP);
 	caps &= GENMASK(2, 0);
 
+	dev_dbg(&adev->dev, "SoundWire links: BIOS count %d hardware caps %d\n",
+		count, caps);
+
 	/* Check HW supported vs property value and use min of two */
 	count = min_t(u8, caps, count);
 
@@ -111,6 +118,13 @@ static struct sdw_intel_ctx
 
 	/* Create SDW Master devices */
 	for (i = 0; i < count; i++) {
+		if (link_mask && !(link_mask & BIT(i))) {
+			dev_dbg(&adev->dev,
+				"Link %d masked, will not be enabled\n", i);
+			link++;
+			continue;
+		}
+
 		link->res.irq = res->irq;
 		link->res.registers = res->mmio_base + SDW_LINK_BASE
 					+ (SDW_LINK_SIZE * i);
-- 
2.20.1