On LoPAR "DMA Window Manipulation Calls", it's recommended to remove the
default DMA window for the device, before attempting to configure a DDW,
in order to make the maximum resources available for the next DDW to be
created.
This is a requirement for using DDW on devices in which hypervisor
allows only one DMA window.
If setting up a new DDW fails anywhere after the removal of this
default DMA window, it's needed to restore the default DMA window.
For this, an implementation of ibm,reset-pe-dma-windows rtas call is
needed:
Platforms supporting the DDW option starting with LoPAR level 2.7 implement
ibm,ddw-extensions. The first extension available (index 2) carries the
token for ibm,reset-pe-dma-windows rtas call, which is used to restore
the default DMA window for a device, if it has been deleted.
It does so by resetting the TCE table allocation for the PE to it's
boot time value, available in "ibm,dma-window" device tree node.
Signed-off-by: Leonardo Bras <leobra...@gmail.com>
Tested-by: David Dai <z...@linux.vnet.ibm.com>
---
arch/powerpc/platforms/pseries/iommu.c | 73 +++++++++++++++++++++++---
1 file changed, 66 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/iommu.c
b/arch/powerpc/platforms/pseries/iommu.c
index 4e33147825cc..e4198700ed1a 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -1066,6 +1066,38 @@ static phys_addr_t ddw_memory_hotplug_max(void)
return max_addr;
}
+/*
+ * Platforms supporting the DDW option starting with LoPAR level 2.7 implement
+ * ibm,ddw-extensions, which carries the rtas token for
+ * ibm,reset-pe-dma-windows.
+ * That rtas-call can be used to restore the default DMA window for the device.
+ */
+static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn)
+{
+ int ret;
+ u32 cfg_addr, reset_dma_win;
+ u64 buid;
+ struct device_node *dn;
+ struct pci_dn *pdn;
+
+ ret = ddw_read_ext(par_dn, DDW_EXT_RESET_DMA_WIN, &reset_dma_win);
+ if (ret)
+ return;
+
+ dn = pci_device_to_OF_node(dev);
+ pdn = PCI_DN(dn);
+ buid = pdn->phb->buid;
+ cfg_addr = (pdn->busno << 16) | (pdn->devfn << 8);
+
+ ret = rtas_call(reset_dma_win, 3, 1, NULL, cfg_addr, BUID_HI(buid),
+ BUID_LO(buid));
+ if (ret)
+ dev_info(&dev->dev,
+ "ibm,reset-pe-dma-windows(%x) %x %x %x returned %d ",
+ reset_dma_win, cfg_addr, BUID_HI(buid), BUID_LO(buid),
+ ret);
+}
+
/*
* If the PE supports dynamic dma windows, and there is space for a table
* that can map all pages in a linear offset, then setup such a table,
@@ -1090,6 +1122,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct
device_node *pdn)
struct property *win64;
struct dynamic_dma_window_prop *ddwprop;
struct failed_ddw_pdn *fpdn;
+ bool default_win_removed = false;
mutex_lock(&direct_window_init_mutex);
@@ -1133,14 +1166,38 @@ static u64 enable_ddw(struct pci_dev *dev, struct
device_node *pdn)
if (ret != 0)
goto out_failed;
+ /*
+ * If there is no window available, remove the default DMA window,
+ * if it's present. This will make all the resources available to the
+ * new DDW window.
+ * If anything fails after this, we need to restore it, so also check
+ * for extensions presence.
+ */
if (query.windows_available == 0) {
- /*
- * no additional windows are available for this device.
- * We might be able to reallocate the existing window,
- * trading in for a larger page size.
- */
- dev_dbg(&dev->dev, "no free dynamic windows");
- goto out_failed;
+ struct property *default_win;
+ int reset_win_ext;
+
+ default_win = of_find_property(pdn, "ibm,dma-window", NULL);
+ if (!default_win)
+ goto out_failed;
+
+ reset_win_ext = ddw_read_ext(pdn, DDW_EXT_RESET_DMA_WIN, NULL);
+ if (reset_win_ext)
+ goto out_failed;
+
+ remove_dma_window(pdn, ddw_avail, default_win);
+ default_win_removed = true;
+
+ /* Query again, to check if the window is available */
+ ret = query_ddw(dev, ddw_avail, &query, pdn);
+ if (ret != 0)
+ goto out_failed;
+
+ if (query.windows_available == 0) {
+ /* no windows are available for this device. */
+ dev_dbg(&dev->dev, "no free dynamic windows");
+ goto out_failed;
+ }
}
if (query.page_size & 4) {
page_shift = 24; /* 16MB */
@@ -1231,6 +1288,8 @@ static u64 enable_ddw(struct pci_dev *dev, struct
device_node *pdn)
kfree(win64);
out_failed:
+ if (default_win_removed)
+ reset_dma_window(dev, pdn);
fpdn = kzalloc(sizeof(*fpdn), GFP_KERNEL);
if (!fpdn)
--
2.25.4
