Re: [PATCH v2] coresight: tmc: Don't enable TMC when it's not ready.

Hi Mike,

Thanks for the comments, please note that I have queued this patch for next.

On 01/02/2023 20:43, Mike Leach wrote:

Hi,

On Fri, 27 Jan 2023 at 23:10, Yabin Cui yabinc@google.com wrote:

...

If TMC ETR is enabled without being ready, in later use we may see AXI bus errors caused by accessing invalid addresses.

Signed-off-by: Yabin Cui yabinc@google.com

V1 -> V2: Make change to all TMCs instead of just ETR

.../hwtracing/coresight/coresight-tmc-core.c | 4 +- .../hwtracing/coresight/coresight-tmc-etf.c | 43 +++++++++++++++---- .../hwtracing/coresight/coresight-tmc-etr.c | 18 ++++++-- drivers/hwtracing/coresight/coresight-tmc.h | 2 +- 4 files changed, 53 insertions(+), 14 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c index 07abf28ad725..c106d142e632 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-core.c +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c @@ -31,7 +31,7 @@ DEFINE_CORESIGHT_DEVLIST(etb_devs, "tmc_etb"); DEFINE_CORESIGHT_DEVLIST(etf_devs, "tmc_etf"); DEFINE_CORESIGHT_DEVLIST(etr_devs, "tmc_etr");

-void tmc_wait_for_tmcready(struct tmc_drvdata *drvdata) +int tmc_wait_for_tmcready(struct tmc_drvdata *drvdata) { struct coresight_device *csdev = drvdata->csdev; struct csdev_access *csa = &csdev->access; @@ -40,7 +40,9 @@ void tmc_wait_for_tmcready(struct tmc_drvdata *drvdata) if (coresight_timeout(csa, TMC_STS, TMC_STS_TMCREADY_BIT, 1)) { dev_err(&csdev->dev, "timeout while waiting for TMC to be Ready\n");

•           return -EBUSY;
     }
  

•   return 0;
  

  }

  void tmc_flush_and_stop(struct tmc_drvdata *drvdata)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c index 4c4cbd1f7258..2840227e9135 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c @@ -16,12 +16,19 @@ static int tmc_set_etf_buffer(struct coresight_device *csdev, struct perf_output_handle *handle);

-static void __tmc_etb_enable_hw(struct tmc_drvdata *drvdata) +static int __tmc_etb_enable_hw(struct tmc_drvdata *drvdata) {

•   int rc = 0;
  

•    CS_UNLOCK(drvdata->base);
  
     /* Wait for TMCSReady bit to be set */
  

•   tmc_wait_for_tmcready(drvdata);
  

•   rc = tmc_wait_for_tmcready(drvdata);
  

•   if (rc) {
  

•           dev_err(&drvdata->csdev->dev, "fails to enable not ready TMC\n");
  

•           CS_LOCK(drvdata->base);
  

•           return rc;
  

•   }
  
     writel_relaxed(TMC_MODE_CIRCULAR_BUFFER, drvdata->base + TMC_MODE);
     writel_relaxed(TMC_FFCR_EN_FMT | TMC_FFCR_EN_TI |
  

@@ -33,6 +40,7 @@ static void __tmc_etb_enable_hw(struct tmc_drvdata *drvdata) tmc_enable_hw(drvdata);

     CS_LOCK(drvdata->base);

•   return rc;
  

  }

  static int tmc_etb_enable_hw(struct tmc_drvdata *drvdata)

@@ -42,8 +50,10 @@ static int tmc_etb_enable_hw(struct tmc_drvdata *drvdata) if (rc) return rc;

•   __tmc_etb_enable_hw(drvdata);
  

•   return 0;
  

•   rc = __tmc_etb_enable_hw(drvdata);
  

•   if (rc)
  

•           coresight_disclaim_device(drvdata->csdev);
  

•   return rc;
  

  }

  static void tmc_etb_dump_hw(struct tmc_drvdata *drvdata)

@@ -91,12 +101,19 @@ static void tmc_etb_disable_hw(struct tmc_drvdata *drvdata) coresight_disclaim_device(drvdata->csdev); }

-static void __tmc_etf_enable_hw(struct tmc_drvdata *drvdata) +static int __tmc_etf_enable_hw(struct tmc_drvdata *drvdata) {

•   int rc = 0;
  

•    CS_UNLOCK(drvdata->base);
  
     /* Wait for TMCSReady bit to be set */
  

•   tmc_wait_for_tmcready(drvdata);
  

•   rc = tmc_wait_for_tmcready(drvdata);
  

•   if (rc) {
  

•           dev_err(&drvdata->csdev->dev, "fails to enable not ready TMC\n");
  

•           CS_LOCK(drvdata->base);
  

•           return rc;
  

•   }
  
     writel_relaxed(TMC_MODE_HARDWARE_FIFO, drvdata->base + TMC_MODE);
     writel_relaxed(TMC_FFCR_EN_FMT | TMC_FFCR_EN_TI,
  

@@ -105,6 +122,7 @@ static void __tmc_etf_enable_hw(struct tmc_drvdata *drvdata) tmc_enable_hw(drvdata);

     CS_LOCK(drvdata->base);

•   return rc;
  

  }

  static int tmc_etf_enable_hw(struct tmc_drvdata *drvdata)

@@ -114,8 +132,10 @@ static int tmc_etf_enable_hw(struct tmc_drvdata *drvdata) if (rc) return rc;

•   __tmc_etf_enable_hw(drvdata);
  

•   return 0;
  

•   rc = __tmc_etf_enable_hw(drvdata);
  

•   if (rc)
  

•           coresight_disclaim_device(drvdata->csdev);
  

•   return rc;
  

  }

  static void tmc_etf_disable_hw(struct tmc_drvdata *drvdata)

@@ -639,6 +659,7 @@ int tmc_read_unprepare_etb(struct tmc_drvdata *drvdata) char *buf = NULL; enum tmc_mode mode; unsigned long flags;

•   int rc = 0;
  
     /* config types are set a boot time and never change */
     if (WARN_ON_ONCE(drvdata->config_type != TMC_CONFIG_TYPE_ETB &&
  

@@ -664,7 +685,11 @@ int tmc_read_unprepare_etb(struct tmc_drvdata *drvdata) * can't be NULL. */ memset(drvdata->buf, 0, drvdata->size);

•           __tmc_etb_enable_hw(drvdata);
  

•           rc = __tmc_etb_enable_hw(drvdata);
  

•           if (rc) {
  

•                   spin_unlock_irqrestore(&drvdata->spinlock, flags);
  

•                   return rc;
  

•           }
  

There is a similar unprepare function in ETR - this should have similar updates.

...

     } else {
             /*
              * The ETB/ETF is not tracing and the buffer was just read.

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c index 867ad8bb9b0c..0811cb44588b 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -983,15 +983,21 @@ static void tmc_sync_etr_buf(struct tmc_drvdata *drvdata) etr_buf->ops->sync(etr_buf, rrp, rwp); }

-static void __tmc_etr_enable_hw(struct tmc_drvdata *drvdata) +static int __tmc_etr_enable_hw(struct tmc_drvdata *drvdata) { u32 axictl, sts; struct etr_buf *etr_buf = drvdata->etr_buf;

•   int rc = 0;
  
     CS_UNLOCK(drvdata->base);
  
     /* Wait for TMCSReady bit to be set */
  

•   tmc_wait_for_tmcready(drvdata);
  

•   rc = tmc_wait_for_tmcready(drvdata);
  

•   if (rc) {
  

•           dev_err(&drvdata->csdev->dev, "fails to enable not ready TMC\n");
  

•           CS_LOCK(drvdata->base);
  

•           return rc;
  

•   }
  
     writel_relaxed(etr_buf->size / 4, drvdata->base + TMC_RSZ);
     writel_relaxed(TMC_MODE_CIRCULAR_BUFFER, drvdata->base + TMC_MODE);
  

@@ -1032,6 +1038,7 @@ static void __tmc_etr_enable_hw(struct tmc_drvdata *drvdata) tmc_enable_hw(drvdata);

     CS_LOCK(drvdata->base);

•   return rc;
  

  }

  static int tmc_etr_enable_hw(struct tmc_drvdata *drvdata,

@@ -1060,7 +1067,12 @@ static int tmc_etr_enable_hw(struct tmc_drvdata *drvdata, rc = coresight_claim_device(drvdata->csdev); if (!rc) { drvdata->etr_buf = etr_buf;

•           __tmc_etr_enable_hw(drvdata);
  

•           rc = __tmc_etr_enable_hw(drvdata);
  

•           if (rc) {
  

•                   drvdata->etr_buf = NULL;
  

•                   coresight_disclaim_device(drvdata->csdev);
  

•                   tmc_etr_disable_catu(drvdata);
  

•           }
     }
  
     return rc;
  

diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h index 66959557cf39..01c0382a29c0 100644 --- a/drivers/hwtracing/coresight/coresight-tmc.h +++ b/drivers/hwtracing/coresight/coresight-tmc.h @@ -255,7 +255,7 @@ struct tmc_sg_table { };

/* Generic functions */ -void tmc_wait_for_tmcready(struct tmc_drvdata *drvdata); +int tmc_wait_for_tmcready(struct tmc_drvdata *drvdata); void tmc_flush_and_stop(struct tmc_drvdata *drvdata); void tmc_enable_hw(struct tmc_drvdata *drvdata); void tmc_disable_hw(struct tmc_drvdata *drvdata); -- 2.39.1.456.gfc5497dd1b-goog

The tmc_flush_and_stop() function also calls tmc_wait_for_tmcready().

I think this already an error message there, when it fails to complete the flush.I thought of adding a WARN_ON, but thought it is not worth much.

The etb/etf_prepare_read operations disable the etb /etf before a read commences. For consistency if this fails due to TMC not being ready do we also need to fail the read prepare operations?

I think that should be OK, as we can read what the TMC has already flushed/written to the memory. A following session may not be able to use the ETR, which is fine.

Cheers Suzuki

Regards

Mike