diff mbox

[5/7] CXL: Disable AFU debug flag

Message ID 1418026681-14787-5-git-send-email-imunsie@au.ibm.com (mailing list archive)
State Accepted
Commit d6a6af2c181400aade59417e698c7cd9bec8804e
Delegated to: Michael Ellerman
Headers show

Commit Message

Ian Munsie Dec. 8, 2014, 8:17 a.m. UTC
From: Ian Munsie <imunsie@au1.ibm.com>

Upon inspection of the implementation specific registers, it was
discovered that the high bit of the implementation specific RXCTL
register was enabled, which enables the DEADB00F debug feature.

The debug feature causes MMIO reads to a disabled AFU to respond with
0xDEADB00F instead of all Fs. In general this should not be visible as
the kernel will only allow MMIO access to enabled AFUs, but there may be
some circumstances where an AFU may become disabled while it is use.
One such case would be an AFU designed to only be used in the dedicated
process mode and to disable itself after it has completed it's work
(however even in that case the effects of this debug flag would be
limited as the userspace application must have completed any required
MMIO accesses before the AFU disables itself with or without the flag).

This patch removes the debug flag and replaces the magic value
programmed into this register with a preprocessor define so it is
clearer what the rest of this initialisation does.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
---
 drivers/misc/cxl/cxl.h | 7 +++++++
 drivers/misc/cxl/pci.c | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

Comments

Ian Munsie Dec. 9, 2014, 5:39 a.m. UTC | #1
This one would be nice to go to stable, but I'm not sure it really meets
the rules. It could be a problem for userspace error paths checking the
result of MMIO reads, but only if the AFU has actually been unexpectedly
disabled somehow yet the PSL is still responding...

I don't think this is a high priority to go to stable unless it starts
causing problems for someone.

Cheers,
-Ian
diff mbox

Patch

diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
index 7c05239..c1f8aa6 100644
--- a/drivers/misc/cxl/cxl.h
+++ b/drivers/misc/cxl/cxl.h
@@ -287,6 +287,13 @@  static const cxl_p2n_reg_t CXL_PSL_WED_An     = {0x0A0};
 #define CXL_PE_SOFTWARE_STATE_S (1ul << (31 - 30)) /* Suspend */
 #define CXL_PE_SOFTWARE_STATE_T (1ul << (31 - 31)) /* Terminate */
 
+/****** CXL_PSL_RXCTL_An (Implementation Specific) **************************
+ * Controls AFU Hang Pulse, which sets the timeout for the AFU to respond to
+ * the PSL for any response (except MMIO). Timeouts will occur between 1x to 2x
+ * of the hang pulse frequency.
+ */
+#define CXL_PSL_RXCTL_AFUHP_4S      0x7000000000000000ULL
+
 /* SPA->sw_command_status */
 #define CXL_SPA_SW_CMD_MASK         0xffff000000000000ULL
 #define CXL_SPA_SW_CMD_TERMINATE    0x0001000000000000ULL
diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 0f2cc9f..2ccd0a9 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -348,7 +348,7 @@  static int init_implementation_afu_regs(struct cxl_afu *afu)
 	cxl_p1n_write(afu, CXL_PSL_COALLOC_A, 0xFF000000FEFEFEFEULL);
 	/* for debugging with trace arrays */
 	cxl_p1n_write(afu, CXL_PSL_SLICE_TRACE, 0x0000FFFF00000000ULL);
-	cxl_p1n_write(afu, CXL_PSL_RXCTL_A, 0xF000000000000000ULL);
+	cxl_p1n_write(afu, CXL_PSL_RXCTL_A, CXL_PSL_RXCTL_AFUHP_4S);
 
 	return 0;
 }