[PATCH v3 6/6] ipmi: kcs_bmc_aspeed: add clock control logic

[jae.hyun.yoo@intel.com]

From: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>

If LPC KCS driver is registered ahead of lpc-ctrl module, LPC
KCS block will be enabled without heart beating of LCLK until
lpc-ctrl enables the LCLK. This issue causes improper handling on
host interrupts when the host sends interrupts in that time frame.
Then kernel eventually forcibly disables the interrupt with
dumping stack and printing a 'nobody cared this irq' message out.

To prevent this issue, all LPC sub drivers should enable LCLK
individually so this patch adds clock control logic into the LPC
KCS driver.

Note: dtsi change in this patch series should be applied along with,
and dtbs should be re-compiled after applying this series since
it's adding a new required property otherwise this driver will not
be probed correctly.

Fixes: be2ed207e374 ("ipmi: add an Aspeed KCS IPMI BMC driver")
Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
---
v2 -> v3:
 * Simplified the -EPROBE_DEFER handling using dev_err_probe().

v1 -> v2:
 * No change.

 drivers/char/ipmi/kcs_bmc_aspeed.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/char/ipmi/kcs_bmc_aspeed.c b/drivers/char/ipmi/kcs_bmc_aspeed.c
index 92a37b33494c..66c9f51ae611 100644
--- a/drivers/char/ipmi/kcs_bmc_aspeed.c
+++ b/drivers/char/ipmi/kcs_bmc_aspeed.c
@@ -6,6 +6,7 @@
 #define pr_fmt(fmt) "aspeed-kcs-bmc: " fmt
 
 #include <linux/atomic.h>
+#include <linux/clk.h>
 #include <linux/errno.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
@@ -126,6 +127,8 @@ struct aspeed_kcs_bmc {
 		bool remove;
 		struct timer_list timer;
 	} obe;
+
+	struct clk *clk;
 };
 
 struct aspeed_kcs_of_ops {
@@ -620,24 +623,34 @@ static int aspeed_kcs_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
+	priv->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(priv->clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(priv->clk),
+				     "Couldn't get clock\n");
+	rc = clk_prepare_enable(priv->clk);
+	if (rc) {
+		dev_err(&pdev->dev, "Couldn't enable clock\n");
+		return rc;
+	}
+
 	spin_lock_init(&priv->obe.lock);
 	priv->obe.remove = false;
 	timer_setup(&priv->obe.timer, aspeed_kcs_check_obe, 0);
 
 	rc = aspeed_kcs_set_address(kcs_bmc, addrs, nr_addrs);
 	if (rc)
-		return rc;
+		goto err;
 
 	/* Host to BMC IRQ */
 	rc = aspeed_kcs_config_downstream_irq(kcs_bmc, pdev);
 	if (rc)
-		return rc;
+		goto err;
 
 	/* BMC to Host IRQ */
 	if (have_upstream_irq) {
 		rc = aspeed_kcs_config_upstream_irq(priv, upstream_irq[0], upstream_irq[1]);
 		if (rc < 0)
-			return rc;
+			goto err;
 	} else {
 		priv->upstream_irq.mode = aspeed_kcs_irq_none;
 	}
@@ -650,13 +663,19 @@ static int aspeed_kcs_probe(struct platform_device *pdev)
 	rc = kcs_bmc_add_device(&priv->kcs_bmc);
 	if (rc) {
 		dev_warn(&pdev->dev, "Failed to register channel %d: %d\n", kcs_bmc->channel, rc);
-		return rc;
+		goto err;
 	}
 
 	dev_info(&pdev->dev, "Initialised channel %d at 0x%x\n",
 			kcs_bmc->channel, addrs[0]);
 
 	return 0;
+
+err:
+	aspeed_kcs_enable_channel(kcs_bmc, false);
+	clk_disable_unprepare(priv->clk);
+
+	return rc;
 }
 
 static int aspeed_kcs_remove(struct platform_device *pdev)
@@ -664,6 +683,7 @@ static int aspeed_kcs_remove(struct platform_device *pdev)
 	struct aspeed_kcs_bmc *priv = platform_get_drvdata(pdev);
 	struct kcs_bmc_device *kcs_bmc = &priv->kcs_bmc;
 
+	clk_disable_unprepare(priv->clk);
 	kcs_bmc_remove_device(kcs_bmc);
 
 	aspeed_kcs_enable_channel(kcs_bmc, false);
-- 
2.25.1