[PATCH v2 10/12] coresight tmc: Support for save-restore in ETR

From: Suzuki K Poulose
Date: Mon Jun 26 2017 - 11:25:47 EST


The Coresight SoC 600 TMC ETR supports save-restore feature,
where the values of the RRP/RWP and STS.Full are retained
when it leaves the Disabled state. Hence, we must program the
RRP/RWP and STS.Full to a proper value. For now, set the RRP/RWP
to the base address of the buffer and clear the STS.Full register.
This can be later exploited for proper save-restore of ETR
trace contexts (e.g, perf).

Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
drivers/hwtracing/coresight/coresight-tmc-etr.c | 13 ++++++++++++-
drivers/hwtracing/coresight/coresight-tmc.h | 8 ++++++++
2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index ff11b92..7294fb7 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -22,7 +22,7 @@

static void tmc_etr_enable_hw(struct tmc_drvdata *drvdata)
{
- u32 axictl;
+ u32 axictl, sts;

/* Zero out the memory to help with debug */
memset(drvdata->vaddr, 0, drvdata->size);
@@ -45,6 +45,17 @@ static void tmc_etr_enable_hw(struct tmc_drvdata *drvdata)
TMC_AXICTL_PROT_CTL_B1;
writel_relaxed(axictl, drvdata->base + TMC_AXICTL);
tmc_write_dba(drvdata, drvdata->paddr);
+ /*
+ * If the TMC pointers must be programmed before the session,
+ * we have to set it properly (i.e, RRP/RWP to base address and
+ * STS to "not full").
+ */
+ if (tmc_has_cap(drvdata, TMC_CAP_ETR_SAVE_RESTORE)) {
+ tmc_write_rrp(drvdata, drvdata->paddr);
+ tmc_write_rwp(drvdata, drvdata->paddr);
+ sts = readl_relaxed(drvdata->base + TMC_STS) & ~TMC_STS_FULL;
+ writel_relaxed(sts, drvdata->base + TMC_STS);
+ }

writel_relaxed(TMC_FFCR_EN_FMT | TMC_FFCR_EN_TI |
TMC_FFCR_FON_FLIN | TMC_FFCR_FON_TRIG_EVT |
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index 87e4561..d5ef51e 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -90,6 +90,14 @@ enum tmc_mem_intf_width {
};

#define TMC_CAP_ETR_SG_UNIT (1U << 0)
+/*
+ * TMC_CAP_ETR_SAVE_RESTORE - Values of RRP/RWP/STS.Full are
+ * retained when TMC leaves Disabled state, allowing us to continue
+ * the tracing from a point where we stopped. This also implies that
+ * the RRP/RWP/STS.Full should always be programmed to the correct
+ * value.
+ */
+#define TMC_CAP_ETR_SAVE_RESTORE (1U << 1)

/**
* struct tmc_cap - Describes the capabilities of the TMC.
--
2.7.5