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Disable decoding of BARs by devices before we trash the value in the BAR

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by writing all 1's to it to determine its length.  This fixes issues with
MCFG on at least some machines where a trashed BAR claimed subsequent
attempts at PCI config transactions because the addresses in the MCFG
window fell in the decoding range of the BAR.

In general it is a bad idea to leave the BARs enabled while we are
frobbing with them in this manner.

Sleuthing by:  tegge
MFC after:     1 week
This commit is contained in:
jhb 2009-01-16 22:22:30 +00:00
parent c8283e83be
commit 9d7c60d6cd
1 changed files with 18 additions and 0 deletions
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18
sys/dev/pci/pci.c
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@ -2291,9 +2291,27 @@ pci_add_map(device_t pcib, device_t bus, device_t dev,
struct resource *res;
map = PCIB_READ_CONFIG(pcib, b, s, f, reg, 4);
/*
* Disable decoding via the command register before
* determining the BARs length since we will be placing them
* in a weird state.
*/
cmd = PCIB_READ_CONFIG(pcib, b, s, f, PCIR_COMMAND, 2);
PCIB_WRITE_CONFIG(pcib, b, s, f, PCIR_COMMAND,
cmd & ~(PCI_BAR_MEM(map) ? PCIM_CMD_MEMEN : PCIM_CMD_PORTEN), 2);
/*
* Determine the BAR's length by writing all 1's. The bottom
* log_2(size) bits of the BAR will stick as 0 when we read
* the value back.
*/
PCIB_WRITE_CONFIG(pcib, b, s, f, reg, 0xffffffff, 4);
testval = PCIB_READ_CONFIG(pcib, b, s, f, reg, 4);
/* Restore the BAR and command register. */
PCIB_WRITE_CONFIG(pcib, b, s, f, reg, map, 4);
PCIB_WRITE_CONFIG(pcib, b, s, f, PCIR_COMMAND, cmd, 2);
if (PCI_BAR_MEM(map))
type = SYS_RES_MEMORY;