From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932767AbcDSPpu (ORCPT ); Tue, 19 Apr 2016 11:45:50 -0400 Received: from mail-vk0-f51.google.com ([209.85.213.51]:36263 "EHLO mail-vk0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932667AbcDSPps (ORCPT ); Tue, 19 Apr 2016 11:45:48 -0400 MIME-Version: 1.0 In-Reply-To: <57163075.5030107@arm.com> References: <1460483692-25061-1-git-send-email-mathieu.poirier@linaro.org> <1460483692-25061-10-git-send-email-mathieu.poirier@linaro.org> <57163075.5030107@arm.com> Date: Tue, 19 Apr 2016 09:45:46 -0600 Message-ID: Subject: Re: [PATCH V2 09/15] coresight: tmc: adding mode of operation for link/sinks From: Mathieu Poirier To: Suzuki K Poulose Cc: "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19 April 2016 at 07:19, Suzuki K Poulose 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 >> --- >> 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. > >> /* >> * 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 ? You are correct, using a local_t variable isn't strictly needed here. But: 1) It greatly simplifies the code. 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. Mathieu > > Suzuki > From mboxrd@z Thu Jan 1 00:00:00 1970 From: mathieu.poirier@linaro.org (Mathieu Poirier) Date: Tue, 19 Apr 2016 09:45:46 -0600 Subject: [PATCH V2 09/15] coresight: tmc: adding mode of operation for link/sinks In-Reply-To: <57163075.5030107@arm.com> References: <1460483692-25061-1-git-send-email-mathieu.poirier@linaro.org> <1460483692-25061-10-git-send-email-mathieu.poirier@linaro.org> <57163075.5030107@arm.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 19 April 2016 at 07:19, Suzuki K Poulose 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 >> --- >> 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. > >> /* >> * 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 ? You are correct, using a local_t variable isn't strictly needed here. But: 1) It greatly simplifies the code. 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. Mathieu > > Suzuki >