[PATCH 23/31] coresight: etm4x: Add necessary synchronization for sysreg access
From: Mathieu Poirier <mathieu.poirier@linaro.org>
Date: 2021-02-01 18:30:56
Also in:
lkml
Subsystem:
arm/coresight framework and drivers, hardware tracing facilities, the rest · Maintainers:
Suzuki K Poulose, Alexander Shishkin, Linus Torvalds
From: Suzuki K Poulose <suzuki.poulose@arm.com> As per the specification any update to the TRCPRGCTLR must be synchronized by a context synchronization event (in our case an explicist ISB) before the TRCSTATR is checked. Cc: Mike Leach <redacted> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Link: https://lore.kernel.org/r/20210110224850.1880240-22-suzuki.poulose@arm.com (local) Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> --- drivers/hwtracing/coresight/coresight-etm4x-core.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index a09a653fc5b0..8d644e93de51 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c@@ -284,6 +284,15 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata) /* Disable the trace unit before programming trace registers */ etm4x_relaxed_write32(csa, 0, TRCPRGCTLR); + /* + * If we use system instructions, we need to synchronize the + * write to the TRCPRGCTLR, before accessing the TRCSTATR. + * See ARM IHI0064F, section + * "4.3.7 Synchronization of register updates" + */ + if (!csa->io_mem) + isb(); + /* wait for TRCSTATR.IDLE to go up */ if (coresight_timeout(csa, TRCSTATR, TRCSTATR_IDLE_BIT, 1)) dev_err(etm_dev,
@@ -362,6 +371,10 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata) /* Enable the trace unit */ etm4x_relaxed_write32(csa, 1, TRCPRGCTLR); + /* Synchronize the register updates for sysreg access */ + if (!csa->io_mem) + isb(); + /* wait for TRCSTATR.IDLE to go back down to '0' */ if (coresight_timeout(csa, TRCSTATR, TRCSTATR_IDLE_BIT, 0)) dev_err(etm_dev,
--
2.25.1
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