diff mbox series

[v4,2/6] coresight: etm4x: use explicit barriers on enable/disable

Message ID 20190730125157.884-3-andrew.murray@arm.com (mailing list archive)
State New, archived
Headers show
Series coresight: etm4x: save/restore ETMv4 context across CPU low power states | expand

Commit Message

Andrew Murray July 30, 2019, 12:51 p.m. UTC 
Synchronization is recommended before disabling the trace registers
to prevent any start or stop points being speculative at the point
of disabling the unit (section 7.3.77 of ARM IHI 0064D).

Synchronization is also recommended after programming the trace
registers to ensure all updates are committed prior to normal code
resuming (section 4.3.7 of ARM IHI 0064D).

Let's ensure these syncronization points are present in the code
and clearly commented.

Note that we could rely on the barriers in CS_LOCK and
coresight_disclaim_device_unlocked or the context switch to user
space - however coresight may be of use in the kernel.

On armv8 the mb macro is defined as dsb(sy) - Given that the etm4x is
only used on armv8 let's directly use dsb(sy) instead of mb(). This
removes some ambiguity and makes it easier to correlate the code with
the TRM.

Signed-off-by: Andrew Murray <andrew.murray@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
CC: stable@vger.kernel.org
---
 drivers/hwtracing/coresight/coresight-etm4x.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

Comments

Sasha Levin Aug. 1, 2019, 1:31 p.m. UTC | #1 
Hi,

[This is an automated email]

This commit has been processed because it contains a -stable tag.
The stable tag indicates that it's relevant for the following trees: all

The bot has tested the following trees: v5.2.4, v5.1.21, v4.19.62, v4.14.134, v4.9.186, v4.4.186.

v5.2.4: Build OK!
v5.1.21: Build OK!
v4.19.62: Failed to apply! Possible dependencies:
    41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
    68a147752d04 ("coresight: etmx: Claim devices before use")
    e006d89abedd ("coresight: etm4x: Add support for handling errors")
    e2a1551a881f ("coresight: etm3: Add support for handling errors")

v4.14.134: Failed to apply! Possible dependencies:
    41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
    68a147752d04 ("coresight: etmx: Claim devices before use")
    e006d89abedd ("coresight: etm4x: Add support for handling errors")
    e2a1551a881f ("coresight: etm3: Add support for handling errors")

v4.9.186: Failed to apply! Possible dependencies:
    297ab90f15f6 ("coresight: tmc: Cleanup operation mode handling")
    2cd541402829 ("coresight: tmc: minor fix for output log")
    41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
    68a147752d04 ("coresight: etmx: Claim devices before use")
    c38e505e2701 ("coresight: tmc: Get rid of mode parameter for helper routines")
    e006d89abedd ("coresight: etm4x: Add support for handling errors")
    e2a1551a881f ("coresight: etm3: Add support for handling errors")

v4.4.186: Failed to apply! Possible dependencies:
    1925a470ce69 ("coresight: etm3x: splitting struct etm_drvdata")
    2127154d115d ("coresight: etm3x: implementing user/kernel mode tracing")
    22fd532eaa0c ("coresight: etm3x: adding operation mode for etm_enable()")
    27b10da8fff2 ("coresight: etb10: moving to local atomic operations")
    41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
    52210c8745e4 ("coresight: implementing 'cpu_id()' API")
    68a147752d04 ("coresight: etmx: Claim devices before use")
    882d5e112491 ("coresight: etm3x: implementing perf_enable/disable() API")
    b3e94405941e ("coresight: associating path with session rather than tracer")
    c04148e708c0 ("coresight: etm3x: moving sysFS entries to dedicated file")
    c1f8e57c9e66 ("coresight: etm3x: moving etm_readl/writel to header file")
    e2a1551a881f ("coresight: etm3: Add support for handling errors")
    e827d4550aa3 ("coresight: etb10: adding operation mode for sink->enable()")


NOTE: The patch will not be queued to stable trees until it is upstream.

How should we proceed with this patch?

--
Thanks,
Sasha
Mathieu Poirier Aug. 1, 2019, 2:48 p.m. UTC | #2 
On Thu, 1 Aug 2019 at 07:31, Sasha Levin <sashal@kernel.org> wrote:
>
> Hi,
>
> [This is an automated email]
>
> This commit has been processed because it contains a -stable tag.
> The stable tag indicates that it's relevant for the following trees: all
>
> The bot has tested the following trees: v5.2.4, v5.1.21, v4.19.62, v4.14.134, v4.9.186, v4.4.186.
>
> v5.2.4: Build OK!
> v5.1.21: Build OK!
> v4.19.62: Failed to apply! Possible dependencies:
>     41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
>     68a147752d04 ("coresight: etmx: Claim devices before use")
>     e006d89abedd ("coresight: etm4x: Add support for handling errors")
>     e2a1551a881f ("coresight: etm3: Add support for handling errors")
>
> v4.14.134: Failed to apply! Possible dependencies:
>     41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
>     68a147752d04 ("coresight: etmx: Claim devices before use")
>     e006d89abedd ("coresight: etm4x: Add support for handling errors")
>     e2a1551a881f ("coresight: etm3: Add support for handling errors")
>
> v4.9.186: Failed to apply! Possible dependencies:
>     297ab90f15f6 ("coresight: tmc: Cleanup operation mode handling")
>     2cd541402829 ("coresight: tmc: minor fix for output log")
>     41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
>     68a147752d04 ("coresight: etmx: Claim devices before use")
>     c38e505e2701 ("coresight: tmc: Get rid of mode parameter for helper routines")
>     e006d89abedd ("coresight: etm4x: Add support for handling errors")
>     e2a1551a881f ("coresight: etm3: Add support for handling errors")
>
> v4.4.186: Failed to apply! Possible dependencies:
>     1925a470ce69 ("coresight: etm3x: splitting struct etm_drvdata")
>     2127154d115d ("coresight: etm3x: implementing user/kernel mode tracing")
>     22fd532eaa0c ("coresight: etm3x: adding operation mode for etm_enable()")
>     27b10da8fff2 ("coresight: etb10: moving to local atomic operations")
>     41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
>     52210c8745e4 ("coresight: implementing 'cpu_id()' API")
>     68a147752d04 ("coresight: etmx: Claim devices before use")
>     882d5e112491 ("coresight: etm3x: implementing perf_enable/disable() API")
>     b3e94405941e ("coresight: associating path with session rather than tracer")
>     c04148e708c0 ("coresight: etm3x: moving sysFS entries to dedicated file")
>     c1f8e57c9e66 ("coresight: etm3x: moving etm_readl/writel to header file")
>     e2a1551a881f ("coresight: etm3: Add support for handling errors")
>     e827d4550aa3 ("coresight: etb10: adding operation mode for sink->enable()")
>
>
> NOTE: The patch will not be queued to stable trees until it is upstream.
>
> How should we proceed with this patch?

I have another one like that - will send a separate set that applies correctly.

Thanks for the consideration,
Mathieu

>
> --
> Thanks,
> Sasha
Sasha Levin Aug. 2, 2019, 6:08 p.m. UTC | #3 
Hi,

[This is an automated email]

This commit has been processed because it contains a -stable tag.
The stable tag indicates that it's relevant for the following trees: all

The bot has tested the following trees: v5.2.4, v5.1.21, v4.19.62, v4.14.134, v4.9.186, v4.4.186.

v5.2.4: Build OK!
v5.1.21: Build OK!
v4.19.62: Failed to apply! Possible dependencies:
    41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
    68a147752d04 ("coresight: etmx: Claim devices before use")
    e006d89abedd ("coresight: etm4x: Add support for handling errors")
    e2a1551a881f ("coresight: etm3: Add support for handling errors")

v4.14.134: Failed to apply! Possible dependencies:
    41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
    68a147752d04 ("coresight: etmx: Claim devices before use")
    e006d89abedd ("coresight: etm4x: Add support for handling errors")
    e2a1551a881f ("coresight: etm3: Add support for handling errors")

v4.9.186: Failed to apply! Possible dependencies:
    297ab90f15f6 ("coresight: tmc: Cleanup operation mode handling")
    2cd541402829 ("coresight: tmc: minor fix for output log")
    41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
    68a147752d04 ("coresight: etmx: Claim devices before use")
    c38e505e2701 ("coresight: tmc: Get rid of mode parameter for helper routines")
    e006d89abedd ("coresight: etm4x: Add support for handling errors")
    e2a1551a881f ("coresight: etm3: Add support for handling errors")

v4.4.186: Failed to apply! Possible dependencies:
    1925a470ce69 ("coresight: etm3x: splitting struct etm_drvdata")
    2127154d115d ("coresight: etm3x: implementing user/kernel mode tracing")
    22fd532eaa0c ("coresight: etm3x: adding operation mode for etm_enable()")
    27b10da8fff2 ("coresight: etb10: moving to local atomic operations")
    41a75cdde735 ("coresight: Convert driver messages to dev_dbg")
    52210c8745e4 ("coresight: implementing 'cpu_id()' API")
    68a147752d04 ("coresight: etmx: Claim devices before use")
    882d5e112491 ("coresight: etm3x: implementing perf_enable/disable() API")
    b3e94405941e ("coresight: associating path with session rather than tracer")
    c04148e708c0 ("coresight: etm3x: moving sysFS entries to dedicated file")
    c1f8e57c9e66 ("coresight: etm3x: moving etm_readl/writel to header file")
    e2a1551a881f ("coresight: etm3: Add support for handling errors")
    e827d4550aa3 ("coresight: etb10: adding operation mode for sink->enable()")


NOTE: The patch will not be queued to stable trees until it is upstream.

How should we proceed with this patch?

--
Thanks,
Sasha
diff mbox series

Patch

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index 7ad15651e069..ec9468880c71 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -188,6 +188,13 @@  static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
 		dev_err(etm_dev,
 			"timeout while waiting for Idle Trace Status\n");
 
+	/*
+	 * As recommended by section 4.3.7 ("Synchronization when using the
+	 * memory-mapped interface") of ARM IHI 0064D
+	 */
+	dsb(sy);
+	isb();
+
 done:
 	CS_LOCK(drvdata->base);
 
@@ -453,8 +460,12 @@  static void etm4_disable_hw(void *info)
 	/* EN, bit[0] Trace unit enable bit */
 	control &= ~0x1;
 
-	/* make sure everything completes before disabling */
-	mb();
+	/*
+	 * Make sure everything completes before disabling, as recommended
+	 * by section 7.3.77 ("TRCVICTLR, ViewInst Main Control Register,
+	 * SSTATUS") of ARM IHI 0064D
+	 */
+	dsb(sy);
 	isb();
 	writel_relaxed(control, drvdata->base + TRCPRGCTLR);