[RFC PATCH 28/40] soundwire: intel: handle disabled links

[Pierre-Louis Bossart]

On most hardware platforms, SoundWire interfaces are pin-muxed with
other interfaces (typically DMIC or I2S) and the status of each link
needs to be checked at boot time.

For Intel platforms, the BIOS provides a menu to enable/disable the
links separately, and the information is provided to the OS with an
Intel-specific _DSD property. The same capability will be added to
revisions of the MIPI DisCo specification.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.boss...@linux.intel.com>
---
 drivers/soundwire/intel.c     | 26 ++++++++++++++++++++++----
 include/linux/soundwire/sdw.h |  2 ++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
index 796ac2bc8cea..5947fa8e840b 100644
--- a/drivers/soundwire/intel.c
+++ b/drivers/soundwire/intel.c
@@ -90,6 +90,8 @@
 #define SDW_ALH_STRMZCFG_DMAT          GENMASK(7, 0)
 #define SDW_ALH_STRMZCFG_CHN           GENMASK(19, 16)
 
+#define SDW_INTEL_QUIRK_MASK_BUS_DISABLE       BIT(1)
+
 enum intel_pdi_type {
        INTEL_PDI_IN = 0,
        INTEL_PDI_OUT = 1,
@@ -922,7 +924,7 @@ static int sdw_master_read_intel_prop(struct sdw_bus *bus)
        struct sdw_master_prop *prop = &bus->prop;
        struct fwnode_handle *link;
        char name[32];
-       int nval, i;
+       u32 quirk_mask;
 
        /* Find master handle */
        snprintf(name, sizeof(name),
@@ -937,6 +939,14 @@ static int sdw_master_read_intel_prop(struct sdw_bus *bus)
        fwnode_property_read_u32(link,
                                 "intel-sdw-ip-clock",
                                 &prop->mclk_freq);
+
+       fwnode_property_read_u32(link,
+                                "intel-quirk-mask",
+                                &quirk_mask);
+
+       if (quirk_mask & SDW_INTEL_QUIRK_MASK_BUS_DISABLE)
+               prop->hw_disabled = true;
+
        return 0;
 }
 
@@ -997,6 +1007,12 @@ static int intel_probe(struct platform_device *pdev)
                goto err_master_reg;
        }
 
+       if (sdw->cdns.bus.prop.hw_disabled) {
+               dev_info(&pdev->dev, "SoundWire master %d is disabled, 
ignoring\n",
+                        sdw->cdns.bus.link_id);
+               return 0;
+       }
+
        /* Initialize shim and controller */
        intel_link_power_up(sdw);
        intel_shim_init(sdw);
@@ -1050,9 +1066,11 @@ static int intel_remove(struct platform_device *pdev)
 
        sdw = platform_get_drvdata(pdev);
 
-       intel_debugfs_exit(sdw);
-       free_irq(sdw->res->irq, sdw);
-       snd_soc_unregister_component(sdw->cdns.dev);
+       if (!sdw->cdns.bus.prop.hw_disabled) {
+               intel_debugfs_exit(sdw);
+               free_irq(sdw->res->irq, sdw);
+               snd_soc_unregister_component(sdw->cdns.dev);
+       }
        sdw_delete_bus_master(&sdw->cdns.bus);
 
        return 0;
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index c7dfc824be80..f78b076a8782 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -380,6 +380,7 @@ struct sdw_slave_prop {
  * @err_threshold: Number of times that software may retry sending a single
  * command
  * @mclk_freq: clock reference passed to SoundWire Master, in Hz.
+ * @hw_disabled: if true, the Master is not functional, typically due to 
pin-mux
  */
 struct sdw_master_prop {
        u32 revision;
@@ -395,6 +396,7 @@ struct sdw_master_prop {
        bool dynamic_frame;
        u32 err_threshold;
        u32 mclk_freq;
+       bool hw_disabled;
 };
 
 int sdw_master_read_prop(struct sdw_bus *bus);
-- 
2.20.1