Re: [PATCH v2] coresight: etm4x: Handle accesses to TRCSTALLCTLR

Good day,

On Wed, Jan 27, 2021 at 12:00:32PM +0000, Suzuki K Poulose wrote:

TRCSTALLCTLR register is only implemented if

TRCIDR3.STALLCTL == 0b1

Make sure the driver touches the register only it is implemented.

Cc: stable@vger.kernel.org Cc: Mathieu Poirier mathieu.poirier@linaro.org Cc: Leo Yan leo.yan@linaro.org Cc: Mike Leach mike.leach@linaro.org Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com

---

Changes since v1:

• No change to the patch, fixed the stable email address and added usual reviewers.

---

drivers/hwtracing/coresight/coresight-etm4x-core.c | 9 ++++++--- drivers/hwtracing/coresight/coresight-etm4x-sysfs.c | 3 +++ 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c index b40e3c2bf818..814b49dae0c7 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c @@ -367,7 +367,8 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata) etm4x_relaxed_write32(csa, 0x0, TRCAUXCTLR); etm4x_relaxed_write32(csa, config->eventctrl0, TRCEVENTCTL0R); etm4x_relaxed_write32(csa, config->eventctrl1, TRCEVENTCTL1R);

• etm4x_relaxed_write32(csa, config->stall_ctrl, TRCSTALLCTLR);

• if (drvdata->stallctl)

• etm4x_relaxed_write32(csa, config->stall_ctrl, TRCSTALLCTLR);
  

  etm4x_relaxed_write32(csa, config->ts_ctrl, TRCTSCTLR); etm4x_relaxed_write32(csa, config->syncfreq, TRCSYNCPR); etm4x_relaxed_write32(csa, config->ccctlr, TRCCCCTLR);

@@ -1545,7 +1546,8 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata) state->trcauxctlr = etm4x_read32(csa, TRCAUXCTLR); state->trceventctl0r = etm4x_read32(csa, TRCEVENTCTL0R); state->trceventctl1r = etm4x_read32(csa, TRCEVENTCTL1R);

• state->trcstallctlr = etm4x_read32(csa, TRCSTALLCTLR);

• if (drvdata->stallctl)

• state->trcstallctlr = etm4x_read32(csa, TRCSTALLCTLR);
  

  state->trctsctlr = etm4x_read32(csa, TRCTSCTLR); state->trcsyncpr = etm4x_read32(csa, TRCSYNCPR); state->trcccctlr = etm4x_read32(csa, TRCCCCTLR);

@@ -1657,7 +1659,8 @@ static void etm4_cpu_restore(struct etmv4_drvdata *drvdata) etm4x_relaxed_write32(csa, state->trcauxctlr, TRCAUXCTLR); etm4x_relaxed_write32(csa, state->trceventctl0r, TRCEVENTCTL0R); etm4x_relaxed_write32(csa, state->trceventctl1r, TRCEVENTCTL1R);

• etm4x_relaxed_write32(csa, state->trcstallctlr, TRCSTALLCTLR);

• if (drvdata->stallctl)

• etm4x_relaxed_write32(csa, state->trcstallctlr, TRCSTALLCTLR);
  

  etm4x_relaxed_write32(csa, state->trctsctlr, TRCTSCTLR); etm4x_relaxed_write32(csa, state->trcsyncpr, TRCSYNCPR); etm4x_relaxed_write32(csa, state->trcccctlr, TRCCCCTLR);

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c index 1c490bcef3ad..cd9249fbf913 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c +++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c @@ -296,6 +296,9 @@ static ssize_t mode_store(struct device *dev, if (kstrtoul(buf, 16, &val)) return -EINVAL;

• if ((val & ETM_MODE_ISTALL_EN) && !drvdata->stallctl)

• return -EINVAL;
  

We have two choices here:

1) Follow what is already done in this function for implementation define options like ETM_MODE_BB, ETMv4_MODE_CTXID, ETM_MODE_RETURNSTACK and others. In that case we would have:

/* bit[8], Instruction stall bit */ if ((config->mode & ETM_MODE_ISTALL_EN) && drvdata->stallctl == true)) config->stall_ctrl |= BIT(8); else config->stall_ctrl &= ~BIT(8);

2) Return -EINVAL when something is not supported, like you have above. In that case we'd have to enact the same behavior for all the options, which has the potential of breaking user space.

I think option 1 is best.

Thanks, Mathieu

spin_lock(&drvdata->spinlock); config->mode = val & ETMv4_MODE_ALL; -- 2.24.1