linux-kernel - [PATCH 4.10 45/81] ARCv2: SLC: Make sure busy bit is set properly on SLC flushing

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Date:   Thu,  6 Apr 2017 10:38:37 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alexey Brodkin <abrodkin@...opsys.com>,
        Vineet Gupta <vgupta@...opsys.com>
Subject: [PATCH 4.10 45/81] ARCv2: SLC: Make sure busy bit is set properly on SLC flushing

4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alexey Brodkin <abrodkin@...opsys.com>

commit c70c473396cbdec1168a6eff60e13029c0916854 upstream.

As reported in STAR 9001165532, an SLC control reg read (for checking
busy state) right after SLC invalidate command may incorrectly return
NOT busy causing software to NOT spin-wait while operation is underway.
(and for some reason this only happens if L1 cache is also disabled - as
required by IOC programming model)

Suggested workaround is to do an additional Control Reg read, which
ensures the 2nd read gets the right status.

Signed-off-by: Alexey Brodkin <abrodkin@...opsys.com>
[vgupta: reworte changelog a bit]
Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arc/mm/cache.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/arc/mm/cache.c
+++ b/arch/arc/mm/cache.c
@@ -633,6 +633,9 @@ noinline static void slc_entire_op(const

 	write_aux_reg(ARC_REG_SLC_INVALIDATE, 1);

+	/* Make sure "busy" bit reports correct stataus, see STAR 9001165532 */
+	read_aux_reg(r);
+
 	/* Important to wait for flush to complete */
 	while (read_aux_reg(r) & SLC_CTRL_BUSY);
 }