linux-kernel - [PATCH v3 2/5] soundwire: cadence_master: add hw

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Date:   Tue, 22 Oct 2019 18:54:45 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     alsa-devel@...a-project.org
Cc:     linux-kernel@...r.kernel.org, tiwai@...e.de, broonie@...nel.org,
        vkoul@...nel.org, gregkh@...uxfoundation.org, jank@...ence.com,
        srinivas.kandagatla@...aro.org, slawomir.blauciak@...el.com,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>
Subject: [PATCH v3 2/5] soundwire: cadence_master: add hw_reset capability in debugfs

Provide debugfs capability to kick link and devices into hard-reset
(as defined by MIPI). This capability is really useful when some
devices are no longer responsive and/or to check the software handling
of resynchronization.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
---
 drivers/soundwire/cadence_master.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index 5337ccacccd1..7476e867468d 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -333,6 +333,26 @@ static int cdns_reg_show(struct seq_file *s, void *data)
 }
 DEFINE_SHOW_ATTRIBUTE(cdns_reg);
 
+static int cdns_hw_reset(void *data, u64 value)
+{
+	struct sdw_cdns *cdns = data;
+	int ret;
+
+	if (value != 1)
+		return -EINVAL;
+
+	/* Userspace changed the hardware state behind the kernel's back */
+	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
+
+	ret = sdw_cdns_exit_reset(cdns);
+
+	dev_dbg(cdns->dev, "link hw_reset done: %d\n", ret);
+
+	return ret;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(cdns_hw_reset_fops, NULL, cdns_hw_reset, "%llu\n");
+
 /**
  * sdw_cdns_debugfs_init() - Cadence debugfs init
  * @cdns: Cadence instance
@@ -341,6 +361,9 @@ DEFINE_SHOW_ATTRIBUTE(cdns_reg);
 void sdw_cdns_debugfs_init(struct sdw_cdns *cdns, struct dentry *root)
 {
 	debugfs_create_file("cdns-registers", 0400, root, cdns, &cdns_reg_fops);
+
+	debugfs_create_file("cdns-hw-reset", 0200, root, cdns,
+			    &cdns_hw_reset_fops);
 }
 EXPORT_SYMBOL_GPL(sdw_cdns_debugfs_init);
 
-- 
2.20.1