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SubjectRe: [PATCH V2 09/15] coresight: tmc: adding mode of operation for link/sinks
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On 12/04/16 18:54, Mathieu Poirier wrote:
> Moving tmc_drvdata::enable to a local_t mode. That way the
> sink interface is aware of it's orgin and the foundation for
> mutual exclusion between the sysFS and Perf interface can be
> laid out.
>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
> drivers/hwtracing/coresight/coresight-tmc-etf.c | 28 ++++++++++++++++++-------
> drivers/hwtracing/coresight/coresight-tmc-etr.c | 24 ++++++++++++++++-----
> drivers/hwtracing/coresight/coresight-tmc.h | 4 ++--
> 3 files changed, 42 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index 7cb287ef7b9e..5908000e1ae0 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -110,6 +110,7 @@ static int tmc_enable_etf_sink(struct coresight_device *csdev, u32 mode)
> {
> bool allocated = false;
> char *buf = NULL;
> + u32 val;
> unsigned long flags;
> struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
>
> @@ -146,6 +147,15 @@ fast_path:
> return -EBUSY;
> }
>
> + val = local_xchg(&drvdata->mode, mode);
> + /*
> + * In sysFS mode we can have multiple writers per sink. Since this
> + * sink is already enabled no memory is needed and the HW need not be
> + * touched.
> + */
> + if (val == CS_MODE_SYSFS)
> + goto out;
> +

We are not dropping the spinlock in this case. Are we ?

> /*
> * If drvdata::buf isn't NULL, memory was allocated for a previous
> * trace run but wasn't read. If so simply zero-out the memory.
> @@ -163,9 +173,9 @@ fast_path:
> }
>
> tmc_etb_enable_hw(drvdata);
> - drvdata->enable = true;
> spin_unlock_irqrestore(&drvdata->spinlock, flags);
>
> +out:
> /* Free memory outside the spinlock if need be */
> if (!allocated && buf)
> kfree(buf);

> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index 6022ff26deba..8e6fe267195a 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -85,6 +85,7 @@ static void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
> static int tmc_enable_etr_sink(struct coresight_device *csdev, u32 mode)
> {
> bool allocated = false;
> + u32 val;
> unsigned long flags;
> void __iomem *vaddr = NULL;
> dma_addr_t paddr;
> @@ -125,6 +126,15 @@ fast_path:
> return -EBUSY;
> }
>
> + val = local_xchg(&drvdata->mode, mode);
> + /*
> + * In sysFS mode we can have multiple writers per sink. Since this
> + * sink is already enabled no memory is needed and the HW need not be
> + * touched.
> + */
> + if (val == CS_MODE_SYSFS)
> + goto out;
> +

Same as above, we should drop the locks in this case.

> @@ -140,9 +150,9 @@ fast_path:
> memset(drvdata->vaddr, 0, drvdata->size);
>
> tmc_etr_enable_hw(drvdata);
> - drvdata->enable = true;
> spin_unlock_irqrestore(&drvdata->spinlock, flags);
>
> +out:
> /* Free memory outside the spinlock if need be */
> if (!allocated && vaddr)
> dma_free_coherent(drvdata->dev, drvdata->size, vaddr, paddr);
> @@ -153,6 +163,7 @@ fast_path:

> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
> index 80096fa75326..821bdf150ac9 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.h
> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> @@ -100,7 +100,7 @@ enum tmc_mem_intf_width {
> * @paddr: DMA start location in RAM.
> * @vaddr: virtual representation of @paddr.
> * @size: @buf size.
> - * @enable: this TMC is being used.
> + * @mode: how this TMC is being used.
> * @config_type: TMC variant, must be of type @tmc_config_type.
> * @trigger_cntr: amount of words to store after a trigger.
> */
> @@ -116,7 +116,7 @@ struct tmc_drvdata {
> dma_addr_t paddr;
> void __iomem *vaddr;
> u32 size;
> - bool enable;
> + local_t mode;

Since we always deal with the mode under the spinlock, do we really need this to
be local_t ? Or do we plan to get rid of the lock ?

Suzuki

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