[PATCH 3/7] pci: designware: clamp viewport index

[Ben Dooks]

The current Linux driver for this assumes it can write the 255 into
this register and then read back the value to work out how many
viewports are supported.

Clamp the value so that the probe works and does not cause memory
corruption as the value is not well clamped elsewhere in the driver.

Signed-off-by: Ben Dooks <ben.dooks@sifive.com>
---
 hw/pci-host/designware.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/pci-host/designware.c b/hw/pci-host/designware.c
index d213d7324c..6403416634 100644
--- a/hw/pci-host/designware.c
+++ b/hw/pci-host/designware.c
@@ -345,6 +345,10 @@ static void designware_pcie_root_config_write(PCIDevice 
*d, uint32_t address,
         break;
 
     case DESIGNWARE_PCIE_ATU_VIEWPORT:
+        /* clamp this value, linux uses it to calculate the
+         * available number of viewports */
+        if (val >= DESIGNWARE_PCIE_NUM_VIEWPORTS)
+            val = DESIGNWARE_PCIE_NUM_VIEWPORTS-1;
         root->atu_viewport = val;
         break;
 
-- 
2.35.1