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Subject[PATCH] 2.4.18-pre6 AGP enable fixes
Date
In 2.4.17-pre5, agp_generic_agp_enable() and serverworks_agp_enable()
were changed to look for AGP devices as coprocessors on non-VGA
devices as well as VGA devices.

But those functions contain TWO loops that scan for AGP devices (one
to collect the settings they support, and a second to update the
command registers), and 2.4.17-pre5 only changed the first loop in
each case. Shouldn't both loops be changed, as in the "agp_dev" patch
attached?

While looking at this code, I noticed a possible further improvement.
Currently it looks like this:

pci_for_each_dev(device)
{
if((((device->class >> 16) & 0xFF) != PCI_BASE_CLASS_DISPLAY) &&
(device->class != (PCI_CLASS_PROCESSOR_CO << 8)))
continue;

pci_read_config_dword(device, 0x04, &scratch);

if (!(scratch & 0x00100000))
continue;

pci_read_config_byte(device, 0x34, &cap_ptr);

if (cap_ptr != 0x00) {
do {
pci_read_config_dword(device,
cap_ptr, &cap_id);

if ((cap_id & 0xff) != 0x02)
cap_ptr = (cap_id >> 8) & 0xff;
}
while (((cap_id & 0xff) != 0x02) && (cap_ptr != 0x00));
}
if (cap_ptr != 0x00) {
...

The bulk of the above is just a reimplementation of pci_find_capability(),
so what about changing the whole shooting match to the following:

pci_for_each_dev(device) {
cap_ptr = pci_find_capability(device, PCI_CAP_ID_AGP);
if (cap_ptr != 0x00) {
...

Is there anything gained by checking the device class before looking
for the AGP capability? The "agp_find_cap" patch attached implements
this idea. I've compiled and booted kernels with both patches, but
they're otherwise untested.

--
Bjorn Helgaas - bjorn_helgaas@hp.com
Linux Systems Operation R&D
Hewlett-Packarddiff -u -X /home/helgaas/exclude -r linux-2.4.18-pre6/drivers/char/agp/agpgart_be.c build/linux-2.4.18-pre6/drivers/char/agp/agpgart_be.c
--- linux-2.4.18-pre6/drivers/char/agp/agpgart_be.c Wed Jan 23 10:16:39 2002
+++ build/linux-2.4.18-pre6/drivers/char/agp/agpgart_be.c Wed Jan 23 10:23:23 2002
@@ -506,8 +506,17 @@
* command registers.
*/

- while ((device = pci_find_class(PCI_CLASS_DISPLAY_VGA << 8,
- device)) != NULL) {
+ pci_for_each_dev(device)
+ {
+ /*
+ * Enable AGP devices. Most will be VGA display but
+ * some may be coprocessors on non VGA devices too
+ */
+
+ if((((device->class >> 16) & 0xFF) != PCI_BASE_CLASS_DISPLAY) &&
+ (device->class != (PCI_CLASS_PROCESSOR_CO << 8)))
+ continue;
+
pci_read_config_dword(device, 0x04, &scratch);

if (!(scratch & 0x00100000))
@@ -3421,8 +3430,17 @@
* command registers.
*/

- while ((device = pci_find_class(PCI_CLASS_DISPLAY_VGA << 8,
- device)) != NULL) {
+ pci_for_each_dev(device)
+ {
+ /*
+ * Enable AGP devices. Most will be VGA display but
+ * some may be coprocessors on non VGA devices too
+ */
+
+ if((((device->class >> 16) & 0xFF) != PCI_BASE_CLASS_DISPLAY) &&
+ (device->class != (PCI_CLASS_PROCESSOR_CO << 8)))
+ continue;
+
pci_read_config_dword(device, 0x04, &scratch);

if (!(scratch & 0x00100000))diff -u -X /home/helgaas/exclude -r linux-2.4.18-pre6/drivers/char/agp/agpgart_be.c build/linux-2.4.18-pre6-find_cap/drivers/char/agp/agpgart_be.c
--- linux-2.4.18-pre6/drivers/char/agp/agpgart_be.c Wed Jan 23 10:16:39 2002
+++ build/linux-2.4.18-pre6-find_cap/drivers/char/agp/agpgart_be.c Wed Jan 23 10:32:12 2002
@@ -410,34 +410,8 @@
*/


- pci_for_each_dev(device)
- {
- /*
- * Enable AGP devices. Most will be VGA display but
- * some may be coprocessors on non VGA devices too
- */
-
- if((((device->class >> 16) & 0xFF) != PCI_BASE_CLASS_DISPLAY) &&
- (device->class != (PCI_CLASS_PROCESSOR_CO << 8)))
- continue;
-
- pci_read_config_dword(device, 0x04, &scratch);
-
- if (!(scratch & 0x00100000))
- continue;
-
- pci_read_config_byte(device, 0x34, &cap_ptr);
-
- if (cap_ptr != 0x00) {
- do {
- pci_read_config_dword(device,
- cap_ptr, &cap_id);
-
- if ((cap_id & 0xff) != 0x02)
- cap_ptr = (cap_id >> 8) & 0xff;
- }
- while (((cap_id & 0xff) != 0x02) && (cap_ptr != 0x00));
- }
+ pci_for_each_dev(device) {
+ cap_ptr = pci_find_capability(device, PCI_CAP_ID_AGP);
if (cap_ptr != 0x00) {
/*
* Ok, here we have a AGP device. Disable impossible
@@ -506,25 +480,8 @@
* command registers.
*/

- while ((device = pci_find_class(PCI_CLASS_DISPLAY_VGA << 8,
- device)) != NULL) {
- pci_read_config_dword(device, 0x04, &scratch);
-
- if (!(scratch & 0x00100000))
- continue;
-
- pci_read_config_byte(device, 0x34, &cap_ptr);
-
- if (cap_ptr != 0x00) {
- do {
- pci_read_config_dword(device,
- cap_ptr, &cap_id);
-
- if ((cap_id & 0xff) != 0x02)
- cap_ptr = (cap_id >> 8) & 0xff;
- }
- while (((cap_id & 0xff) != 0x02) && (cap_ptr != 0x00));
- }
+ pci_for_each_dev(device) {
+ cap_ptr = pci_find_capability(device, PCI_CAP_ID_AGP);
if (cap_ptr != 0x00)
pci_write_config_dword(device, cap_ptr + 8, command);
}
@@ -3326,24 +3283,8 @@
*/


- pci_for_each_dev(device)
- {
- /*
- * Enable AGP devices. Most will be VGA display but
- * some may be coprocessors on non VGA devices too
- */
-
- if((((device->class >> 16) & 0xFF) != PCI_BASE_CLASS_DISPLAY) &&
- (device->class != (PCI_CLASS_PROCESSOR_CO << 8)))
- continue;
-
- pci_read_config_dword(device, 0x04, &scratch);
-
- if (!(scratch & 0x00100000))
- continue;
-
- pci_read_config_byte(device, 0x34, &cap_ptr);
-
+ pci_for_each_dev(device) {
+ cap_ptr = pci_find_capability(device, PCI_CAP_ID_AGP);
if (cap_ptr != 0x00) {
do {
pci_read_config_dword(device,
@@ -3421,25 +3362,8 @@
* command registers.
*/

- while ((device = pci_find_class(PCI_CLASS_DISPLAY_VGA << 8,
- device)) != NULL) {
- pci_read_config_dword(device, 0x04, &scratch);
-
- if (!(scratch & 0x00100000))
- continue;
-
- pci_read_config_byte(device, 0x34, &cap_ptr);
-
- if (cap_ptr != 0x00) {
- do {
- pci_read_config_dword(device,
- cap_ptr, &cap_id);
-
- if ((cap_id & 0xff) != 0x02)
- cap_ptr = (cap_id >> 8) & 0xff;
- }
- while (((cap_id & 0xff) != 0x02) && (cap_ptr != 0x00));
- }
+ pci_for_each_dev(device) {
+ cap_ptr = pci_find_capability(device, PCI_CAP_ID_AGP);
if (cap_ptr != 0x00)
pci_write_config_dword(device, cap_ptr + 8, command);
}
@@ -4037,20 +3961,7 @@
#endif /* CONFIG_AGP_SWORKS */

/* find capndx */
- pci_read_config_dword(dev, 0x04, &scratch);
- if (!(scratch & 0x00100000))
- return -ENODEV;
-
- pci_read_config_byte(dev, 0x34, &cap_ptr);
- if (cap_ptr != 0x00) {
- do {
- pci_read_config_dword(dev, cap_ptr, &cap_id);
-
- if ((cap_id & 0xff) != 0x02)
- cap_ptr = (cap_id >> 8) & 0xff;
- }
- while (((cap_id & 0xff) != 0x02) && (cap_ptr != 0x00));
- }
+ cap_ptr = pci_find_capability(dev, PCI_CAP_ID_AGP);
if (cap_ptr == 0x00)
return -ENODEV;
agp_bridge.capndx = cap_ptr;
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