linux-kernel - [char-misc 1/3] mei: me: fix hw ready reset flow

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Date:	Mon, 12 May 2014 12:19:39 +0300
From:	Tomas Winkler <tomas.winkler@...el.com>
To:	gregkh@...uxfoundation.org
Cc:	arnd@...db.de, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, Tomas Winkler <tomas.winkler@...el.com>,
	Alexander Usyskin <alexander.usyskin@...el.com>
Subject: [char-misc 1/3] mei: me: fix hw ready reset flow

We cleared H_RST for H_CSR on spurious interrupt generated when ME_RDY
while cleared and not while  ME_RDY is set. The spurious interrupt
is not delivered on all platforms in this case the
driver may fail to initialize.

Cc: stable@...r.kernel.org
Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
Signed-off-by: Alexander Usyskin <alexander.usyskin@...el.com>
---
 drivers/misc/mei/hw-me.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/mei/hw-me.c b/drivers/misc/mei/hw-me.c
index a31bc4c..ac76a63 100644
--- a/drivers/misc/mei/hw-me.c
+++ b/drivers/misc/mei/hw-me.c
@@ -181,6 +181,9 @@ static void mei_me_hw_reset_release(struct mei_device *dev)
 	hcsr |= H_IG;
 	hcsr &= ~H_RST;
 	mei_hcsr_set(hw, hcsr);
+
+	/* complete this write before we set host ready on another CPU */
+	mmiowb();
 }
 /**
  * mei_me_hw_reset - resets fw via mei csr register.
@@ -218,6 +221,7 @@ static int mei_me_hw_reset(struct mei_device *dev, bool intr_enable)
 static void mei_me_host_set_ready(struct mei_device *dev)
 {
 	struct mei_me_hw *hw = to_me_hw(dev);
+	hw->host_hw_state = mei_hcsr_read(hw);
 	hw->host_hw_state |= H_IE | H_IG | H_RDY;
 	mei_hcsr_set(hw, hw->host_hw_state);
 }
@@ -646,14 +650,13 @@ irqreturn_t mei_me_irq_thread_handler(int irq, void *dev_id)
 	/*  check if we need to start the dev */
 	if (!mei_host_is_ready(dev)) {
 		if (mei_hw_is_ready(dev)) {
+			mei_me_hw_reset_release(dev);
 			dev_dbg(&dev->pdev->dev, "we need to start the dev.\n");
 
 			dev->recvd_hw_ready = true;
 			wake_up_interruptible(&dev->wait_hw_ready);
 		} else {
-
-			dev_dbg(&dev->pdev->dev, "Reset Completed.\n");
-			mei_me_hw_reset_release(dev);
+			dev_dbg(&dev->pdev->dev, "Spurious Interrupt\n");
 		}
 		goto end;
 	}
-- 
1.9.0

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