[PATCH 1/1] PCI: Fix Extend ACS configurability

[Tushar Dave <tdave@nvidia.com>]

Commit 47c8846a49ba ("PCI: Extend ACS configurability") introduced a
bug that fails to configure ACS ctrl for multiple PCI devices. It
affects both 'config_acs' and 'disable_acs_redir'.

For example, using 'config_acs' to configure ACS ctrl for multiple BDFs
fails:

[    0.000000] Kernel command line: pci=config_acs=1111011@0020:02:00.0;101xxxx@0039:00:00.0 "dyndbg=file drivers/pci/pci.c +p" earlycon
[   12.349875] PCI: Can't parse ACS command line parameter
[   19.629314] pci 0020:02:00.0: ACS mask  = 0x007f
[   19.629315] pci 0020:02:00.0: ACS flags = 0x007b
[   19.629316] pci 0020:02:00.0: Configured ACS to 0x007b

After this fix:

[    0.000000] Kernel command line: pci=config_acs=1111011@0020:02:00.0;101xxxx@0039:00:00.0 "dyndbg=file drivers/pci/pci.c +p" earlycon
[   19.583814] pci 0020:02:00.0: ACS mask  = 0x007f
[   19.588532] pci 0020:02:00.0: ACS flags = 0x007b
[   19.593249] pci 0020:02:00.0: ACS control = 0x001d
[   19.598143] pci 0020:02:00.0: Configured ACS to 0x007b
[   24.088699] pci 0039:00:00.0: ACS mask  = 0x0070
[   24.093416] pci 0039:00:00.0: ACS flags = 0x0050
[   24.098136] pci 0039:00:00.0: ACS control = 0x001d
[   24.103031] pci 0039:00:00.0: Configured ACS to 0x005d

For example, using 'disable_acs_redire' fails to clear all three ACS P2P
redir bits:

[    0.000000] Kernel command line: pci=disable_acs_redir=0020:02:00.0;0030:02:00.0;0039:00:00.0 "dyndbg=file drivers/pci/pci.c +p" earlycon
[   19.615860] pci 0020:02:00.0: ACS mask  = 0x002c
[   19.615862] pci 0020:02:00.0: ACS flags = 0xffd3
[   19.615863] pci 0020:02:00.0: Configured ACS to 0xfffb
[   22.332683] pci 0030:02:00.0: ACS mask  = 0x002c
[   22.332685] pci 0030:02:00.0: ACS flags = 0xffd3
[   22.332686] pci 0030:02:00.0: Configured ACS to 0xffdf
[   24.110278] pci 0039:00:00.0: ACS mask  = 0x002c
[   24.110281] pci 0039:00:00.0: ACS flags = 0xffd3
[   24.110283] pci 0039:00:00.0: Configured ACS to 0xffd3

After this fix:

[    0.000000] Kernel command line: pci=disable_acs_redir=0020:02:00.0;0030:02:00.0;0039:00:00.0 "dyndbg=file drivers/pci/pci.c +p" earlycon
[   19.597909] pci 0020:02:00.0: ACS mask  = 0x002c
[   19.597910] pci 0020:02:00.0: ACS flags = 0xffd3
[   19.597911] pci 0020:02:00.0: ACS control = 0x007f
[   19.597911] pci 0020:02:00.0: Configured ACS to 0x0053
[   22.314124] pci 0030:02:00.0: ACS mask  = 0x002c
[   22.314126] pci 0030:02:00.0: ACS flags = 0xffd3
[   22.314127] pci 0030:02:00.0: ACS control = 0x005f
[   22.314128] pci 0030:02:00.0: Configured ACS to 0x0053
[   24.091711] pci 0039:00:00.0: ACS mask  = 0x002c
[   24.091712] pci 0039:00:00.0: ACS flags = 0xffd3
[   24.091714] pci 0039:00:00.0: ACS control = 0x001d
[   24.091715] pci 0039:00:00.0: Configured ACS to 0x0011

Fixes: 47c8846a49ba ("PCI: Extend ACS configurability")
Signed-off-by: Tushar Dave <tdave@nvidia.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 11 +++++------
 drivers/pci/pci.c                               | 16 +++++++++-------
 2 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index dc663c0ca670..fc1c37910d1c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4654,11 +4654,10 @@
 				Format:
 				<ACS flags>@<pci_dev>[; ...]
 				Specify one or more PCI devices (in the format
-				specified above) optionally prepended with flags
-				and separated by semicolons. The respective
-				capabilities will be enabled, disabled or
-				unchanged based on what is specified in
-				flags.
+				specified above) prepended with flags and separated
+				by semicolons. The respective capabilities will be
+				enabled, disabled or unchanged based on what is
+				specified in flags.
 
 				ACS Flags is defined as follows:
 				  bit-0 : ACS Source Validation
@@ -4673,7 +4672,7 @@
 				  '1' – force enabled
 				  'x' – unchanged
 				For example,
-				  pci=config_acs=10x
+				  pci=config_acs=10x@pci:0:0
 				would configure all devices that support
 				ACS to enable P2P Request Redirect, disable
 				Translation Blocking, and leave Source
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 0b29ec6e8e5e..35ff21b014ac 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -951,12 +951,13 @@ static const char *config_acs_param;
 struct pci_acs {
 	u16 cap;
 	u16 ctrl;
-	u16 fw_ctrl;
 };
 
 static void __pci_config_acs(struct pci_dev *dev, struct pci_acs *caps,
-			     const char *p, u16 mask, u16 flags)
+			     const char *p, const u16 acs_mask, const u16 acs_flags)
 {
+	u16 flags = acs_flags;
+	u16 mask = acs_mask;
 	char *delimit;
 	int ret = 0;
 
@@ -964,7 +965,7 @@ static void __pci_config_acs(struct pci_dev *dev, struct pci_acs *caps,
 		return;
 
 	while (*p) {
-		if (!mask) {
+		if (!acs_mask) {
 			/* Check for ACS flags */
 			delimit = strstr(p, "@");
 			if (delimit) {
@@ -972,6 +973,8 @@ static void __pci_config_acs(struct pci_dev *dev, struct pci_acs *caps,
 				u32 shift = 0;
 
 				end = delimit - p - 1;
+				mask = 0;
+				flags = 0;
 
 				while (end > -1) {
 					if (*(p + end) == '0') {
@@ -1028,10 +1031,10 @@ static void __pci_config_acs(struct pci_dev *dev, struct pci_acs *caps,
 
 	pci_dbg(dev, "ACS mask  = %#06x\n", mask);
 	pci_dbg(dev, "ACS flags = %#06x\n", flags);
+	pci_dbg(dev, "ACS control = %#06x\n", caps->ctrl);
 
-	/* If mask is 0 then we copy the bit from the firmware setting. */
-	caps->ctrl = (caps->ctrl & ~mask) | (caps->fw_ctrl & mask);
-	caps->ctrl |= flags;
+	caps->ctrl &= ~mask;
+	caps->ctrl |= (flags & mask);
 
 	pci_info(dev, "Configured ACS to %#06x\n", caps->ctrl);
 }
@@ -1082,7 +1085,6 @@ static void pci_enable_acs(struct pci_dev *dev)
 
 	pci_read_config_word(dev, pos + PCI_ACS_CAP, &caps.cap);
 	pci_read_config_word(dev, pos + PCI_ACS_CTRL, &caps.ctrl);
-	caps.fw_ctrl = caps.ctrl;
 
 	if (enable_acs)
 		pci_std_enable_acs(dev, &caps);
-- 
2.34.1