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Commit 0f7f2fb8 authored by Nathan Lynch's avatar Nathan Lynch Committed by Paul Mackerras
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[POWERPC] Remove gratuitous reads from powermac pci config space methods 



The powermac pci configuration space write methods read the written
location immediately after the write is performed, presumably in order
to flush the write.  However, configuration space writes are not
allowed to be posted, making these reads gratuitous.  Furthermore,
this behavior potentially causes us to violate the PCI PM spec when
changing between e.g. D0 and D3 states, because a delay of up to 10ms
may be required before the OS accesses configuration space after the
write which initiates the transition.

Remove the unnecessary reads from macrisc_write_config,
u3_ht_write_config, and u4_pcie_write_config.

Signed-off-by: default avatarNathan Lynch <ntl@pobox.com>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent b139f1fb

arch/powerpc/platforms/powermac/pci.c

+0 −9
Original line number Diff line number Diff line
@@ -209,15 +209,12 @@ static int macrisc_write_config(struct pci_bus *bus, unsigned int devfn, 
	switch (len) {

	case 1:

		out_8(addr, val);

		(void) in_8(addr);

		break;

	case 2:

		out_le16(addr, val);

		(void) in_le16(addr);

		break;

	default:

		out_le32(addr, val);

		(void) in_le32(addr);

		break;

	}

	return PCIBIOS_SUCCESSFUL;
@@ -440,15 +437,12 @@ static int u3_ht_write_config(struct pci_bus *bus, unsigned int devfn, 
	switch (len) {

	case 1:

		out_8(addr, val);

		(void) in_8(addr);

		break;

	case 2:

		out_le16(addr, val);

		(void) in_le16(addr);

		break;

	default:

		out_le32((u32 __iomem *)addr, val);

		(void) in_le32(addr);

		break;

	}

	return PCIBIOS_SUCCESSFUL;
@@ -545,15 +539,12 @@ static int u4_pcie_write_config(struct pci_bus *bus, unsigned int devfn, 
	switch (len) {

	case 1:

		out_8(addr, val);

		(void) in_8(addr);

		break;

	case 2:

		out_le16(addr, val);

		(void) in_le16(addr);

		break;

	default:

		out_le32(addr, val);

		(void) in_le32(addr);

		break;

	}

	return PCIBIOS_SUCCESSFUL;