[ipxe-devel] [PATCH 1/2] [pci] Add enable_pci_device and disable_pci_device

[Ladi Prosek]

adjust_pci_device unconditionally enables both memory and I/O space
access, which may not be necessary. There was also no way to revert
the device back to the original state.

This commit adds two new functions. enable_pci_device gives drivers
finer control over how the PCI device is initialized and
disable_pci_device is the shutdown path counterpart.

Signed-off-by: Ladi Prosek <lprosek at redhat.com>
Suggested-by: Michael S. Tsirkin <mst at redhat.com>
---
 src/drivers/bus/pci.c  | 41 +++++++++++++++++++++++++++++++++++------
 src/include/ipxe/pci.h |  2 ++
 2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/src/drivers/bus/pci.c b/src/drivers/bus/pci.c
index 6fbedd9..bdff2b9 100644
--- a/src/drivers/bus/pci.c
+++ b/src/drivers/bus/pci.c
@@ -143,16 +143,32 @@ static void pci_read_bases ( struct pci_device *pci ) {
  *
  * @v pci		PCI device
  *
- * Set device to be a busmaster in case BIOS neglected to do so.  Also
- * adjust PCI latency timer to a reasonable value, 32.
+ * Set device to be a busmaster in case BIOS neglected to do so.  Enable
+ * both memory and I/O space access.  Also adjust PCI latency timer to a
+ * reasonable value, 32.
  */
 void adjust_pci_device ( struct pci_device *pci ) {
+	enable_pci_device ( pci,
+			    PCI_COMMAND_MASTER | PCI_COMMAND_MEM |
+			    PCI_COMMAND_IO );
+}
+
+/**
+ * Enable PCI device
+ *
+ * @v pci		PCI device
+ * @v flags		PCI command flags to enable
+ * @ret old_flags	Original PCI command flags
+ *
+ * Enable device in case BIOS neglected to do so.  Also adjust PCI latency
+ * timer to a reasonable value, 32.
+ */
+unsigned enable_pci_device ( struct pci_device *pci, unsigned flags ) {
 	unsigned short new_command, pci_command;
 	unsigned char pci_latency;
 
 	pci_read_config_word ( pci, PCI_COMMAND, &pci_command );
-	new_command = ( pci_command | PCI_COMMAND_MASTER |
-			PCI_COMMAND_MEM | PCI_COMMAND_IO );
+	new_command = ( pci_command | flags );
 	if ( pci_command != new_command ) {
 		DBGC ( pci, PCI_FMT " device not enabled by BIOS! Updating "
 		       "PCI command %04x->%04x\n",
@@ -160,12 +176,25 @@ void adjust_pci_device ( struct pci_device *pci ) {
 		pci_write_config_word ( pci, PCI_COMMAND, new_command );
 	}
 
-	pci_read_config_byte ( pci, PCI_LATENCY_TIMER, &pci_latency);
+	pci_read_config_byte ( pci, PCI_LATENCY_TIMER, &pci_latency );
 	if ( pci_latency < 32 ) {
 		DBGC ( pci, PCI_FMT " latency timer is unreasonably low at "
 		       "%d. Setting to 32.\n", PCI_ARGS ( pci ), pci_latency );
-		pci_write_config_byte ( pci, PCI_LATENCY_TIMER, 32);
+		pci_write_config_byte ( pci, PCI_LATENCY_TIMER, 32 );
 	}
+	return pci_command;
+}
+
+/**
+ * Disable PCI device
+ *
+ * @v pci		PCI device
+ * @v old_flags		Flags to restore, returned from enable_pci_device
+ *
+ * Restore device to state it had before we enabled it.
+ */
+void disable_pci_device ( struct pci_device *pci, unsigned old_flags ) {
+	pci_write_config_word ( pci, PCI_COMMAND, old_flags );
 }
 
 /**
diff --git a/src/include/ipxe/pci.h b/src/include/ipxe/pci.h
index 0c6bc7e..3c613c2 100644
--- a/src/include/ipxe/pci.h
+++ b/src/include/ipxe/pci.h
@@ -278,6 +278,8 @@ struct pci_driver {
 	PCI_FUNC ( (pci)->busdevfn )
 
 extern void adjust_pci_device ( struct pci_device *pci );
+extern unsigned enable_pci_device ( struct pci_device *pci, unsigned flags );
+extern void disable_pci_device ( struct pci_device *pci, unsigned flags );
 extern unsigned long pci_bar_start ( struct pci_device *pci,
 				     unsigned int reg );
 extern int pci_read_config ( struct pci_device *pci );
-- 
2.5.5