intel_th: msu: Preserve pre-existing buffer configuration

The MSU configuration registers may contain buffer address/size set by
the BIOS or an external hardware debugger, which may want to take over
tracing from the driver when the driver is not actively tracing.

Preserve these settings when not actively tracing.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20190705141425.19894-6-alexander.shishkin@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
index b200d9d..fc9f15f 100644 (file)
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -143,6 +143,8 @@ struct msc {
        unsigned int            single_wrap : 1;
        void                    *base;
        dma_addr_t              base_addr;
+       u32                     orig_addr;
+       u32                     orig_sz;
 
        /* <0: no buffer, 0: no users, >0: active users */
        atomic_t                user_count;
@@ -767,6 +769,9 @@ static int msc_configure(struct msc *msc)
                msc_buffer_clear_hw_header(msc);
        }
 
+       msc->orig_addr = ioread32(msc->reg_base + REG_MSU_MSC0BAR);
+       msc->orig_sz   = ioread32(msc->reg_base + REG_MSU_MSC0SIZE);
+
        reg = msc->base_addr >> PAGE_SHIFT;
        iowrite32(reg, msc->reg_base + REG_MSU_MSC0BAR);
 
@@ -841,8 +846,8 @@ static void msc_disable(struct msc *msc)
 
        msc->enabled = 0;
 
-       iowrite32(0, msc->reg_base + REG_MSU_MSC0BAR);
-       iowrite32(0, msc->reg_base + REG_MSU_MSC0SIZE);
+       iowrite32(msc->orig_addr, msc->reg_base + REG_MSU_MSC0BAR);
+       iowrite32(msc->orig_sz, msc->reg_base + REG_MSU_MSC0SIZE);
 
        dev_dbg(msc_dev(msc), "MSCnNWSA: %08x\n",
                ioread32(msc->reg_base + REG_MSU_MSC0NWSA));