ARCv2: SLC: Make sure busy bit is set properly on SLC flushing

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.

Cc: stable@vger.kernel.org  #4.10
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
[vgupta: reworte changelog a bit]
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
index d408fa21a07c9937a0e2956a6e12a7895ffef684..928562967f3cd02fee4a5de34e687d442d64a4e0 100644 (file)
--- a/arch/arc/mm/cache.c
+++ b/arch/arc/mm/cache.c
@@ -633,6 +633,9 @@ noinline static void slc_entire_op(const int op)
 
        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);
 }