Messages in this thread | | | Subject | Re: [PATCH V2 09/15] coresight: tmc: adding mode of operation for link/sinks | From | Suzuki K Poulose <> | Date | Tue, 19 Apr 2016 16:49:35 +0100 |
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On 19/04/16 16:45, Mathieu Poirier wrote: > On 19 April 2016 at 07:19, Suzuki K Poulose <Suzuki.Poulose@arm.com> wrote: >> 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 ? > > Definitely - thanks for pointing that out. > >> >>> 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 ? > > You are correct, using a local_t variable isn't strictly needed here. But: > > 1) It greatly simplifies the code.
+1
> 2) I'm really hoping one day we can do without the spinlocks, though I > don't know when that will happen. > > Get back to me if you're resolute on switching the local_t to a normal type.
No, leave it as it is, as you said, it does simplify the code.
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