[PATCH v2] MHI event ring priority updates

[PATCH v2] MHI event ring priority updates

[Bhaumik Bhatt]

Event ring priorities have remained out of use and are set to 1 by default.
This series brings about an enum entry expanding use of the priority field by
adding high priority tasklet scheduling to the menu.

In some cases, tasklet scheduling delays can be a nuisance. An example would be
ath11k adding a610f3c65d3b ("bus: mhi: Wait for M2 state during system resume")
in response to it. This issue can be potentially avoided if the controller uses
a dedicated event ring for control packets with high priority tasklet scheduling
in place.

There are no functional changes added to the controller (pci_generic or ath11k)
drivers with this series and the only changes there are use of the enum in place
of a harcoded value of "1". In the future, controllers can opt in to have any
event ring scheduled in high priority.

Tested on: X86_64 architecture with SDX65 on Ubuntu 18.04 distribution.

v2:
-Remove enum and update kernel doc for priority simplifying the implementation
-Drop patches for controller changes as they become unnecessary
-Merge adding and enabling of support patches

Hemant Kumar (1):
  bus: mhi: core: Add support for processing priority of event ring

 drivers/bus/mhi/core/init.c | 3 +--
 drivers/bus/mhi/core/main.c | 9 +++++++--
 include/linux/mhi.h         | 2 +-
 3 files changed, 9 insertions(+), 5 deletions(-)

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v2] bus: mhi: core: Add support for processing priority of event ring

[Bhaumik Bhatt]

From: Hemant Kumar <hemantk@codeaurora.org>

Event ring priorities are currently set to 1 and are unused.
Default processing priority for event rings is set to regular
tasklet. Controllers can choose to use high priority tasklet
scheduling for certain event rings critical for processing such
as ones transporting control information if they wish to avoid
system scheduling delays for those packets. In order to support
these use cases, allow controllers to set event ring priority to
high.

Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
---
 drivers/bus/mhi/core/init.c | 3 +--
 drivers/bus/mhi/core/main.c | 9 +++++++--
 include/linux/mhi.h         | 2 +-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index c81b377..4446760 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -673,8 +673,7 @@ static int parse_ev_cfg(struct mhi_controller *mhi_cntrl,
 				&mhi_cntrl->mhi_chan[mhi_event->chan];
 		}
 
-		/* Priority is fixed to 1 for now */
-		mhi_event->priority = 1;
+		mhi_event->priority = event_cfg->priority;
 
 		mhi_event->db_cfg.brstmode = event_cfg->mode;
 		if (MHI_INVALID_BRSTMODE(mhi_event->db_cfg.brstmode))
diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 8ac73f9..3775c77 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -454,10 +454,15 @@ irqreturn_t mhi_irq_handler(int irq_number, void *dev)
 
 		if (mhi_dev)
 			mhi_notify(mhi_dev, MHI_CB_PENDING_DATA);
-	} else {
-		tasklet_schedule(&mhi_event->task);
+
+		return IRQ_HANDLED;
 	}
 
+	if (!mhi_event->priority)
+		tasklet_hi_schedule(&mhi_event->task);
+	else
+		tasklet_schedule(&mhi_event->task);
+
 	return IRQ_HANDLED;
 }
 
diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index 86cea52..bf23c21 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -250,7 +250,7 @@ struct mhi_channel_config {
  * @irq_moderation_ms: Delay irq for additional events to be aggregated
  * @irq: IRQ associated with this ring
  * @channel: Dedicated channel number. U32_MAX indicates a non-dedicated ring
- * @priority: Priority of this ring. Use 1 for now
+ * @priority: Processing priority of this ring. 0 is high and 1 is regular
  * @mode: Doorbell mode
  * @data_type: Type of data this ring will process
  * @hardware_event: This ring is associated with hardware channels
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v2] bus: mhi: core: Add support for processing priority of event ring

[Manivannan Sadhasivam]

On Fri, Jun 18, 2021 at 03:05:03PM -0700, Bhaumik Bhatt wrote:
> From: Hemant Kumar <hemantk@codeaurora.org>
> 
> Event ring priorities are currently set to 1 and are unused.
> Default processing priority for event rings is set to regular
> tasklet. Controllers can choose to use high priority tasklet
> scheduling for certain event rings critical for processing such
> as ones transporting control information if they wish to avoid
> system scheduling delays for those packets. In order to support
> these use cases, allow controllers to set event ring priority to
> high.
> 
> Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Thanks,
Mani

> ---
>  drivers/bus/mhi/core/init.c | 3 +--
>  drivers/bus/mhi/core/main.c | 9 +++++++--
>  include/linux/mhi.h         | 2 +-
>  3 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
> index c81b377..4446760 100644
> --- a/drivers/bus/mhi/core/init.c
> +++ b/drivers/bus/mhi/core/init.c
> @@ -673,8 +673,7 @@ static int parse_ev_cfg(struct mhi_controller *mhi_cntrl,
>  				&mhi_cntrl->mhi_chan[mhi_event->chan];
>  		}
>  
> -		/* Priority is fixed to 1 for now */
> -		mhi_event->priority = 1;
> +		mhi_event->priority = event_cfg->priority;
>  
>  		mhi_event->db_cfg.brstmode = event_cfg->mode;
>  		if (MHI_INVALID_BRSTMODE(mhi_event->db_cfg.brstmode))
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 8ac73f9..3775c77 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -454,10 +454,15 @@ irqreturn_t mhi_irq_handler(int irq_number, void *dev)
>  
>  		if (mhi_dev)
>  			mhi_notify(mhi_dev, MHI_CB_PENDING_DATA);
> -	} else {
> -		tasklet_schedule(&mhi_event->task);
> +
> +		return IRQ_HANDLED;
>  	}
>  
> +	if (!mhi_event->priority)
> +		tasklet_hi_schedule(&mhi_event->task);
> +	else
> +		tasklet_schedule(&mhi_event->task);
> +
>  	return IRQ_HANDLED;
>  }
>  
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index 86cea52..bf23c21 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -250,7 +250,7 @@ struct mhi_channel_config {
>   * @irq_moderation_ms: Delay irq for additional events to be aggregated
>   * @irq: IRQ associated with this ring
>   * @channel: Dedicated channel number. U32_MAX indicates a non-dedicated ring
> - * @priority: Priority of this ring. Use 1 for now
> + * @priority: Processing priority of this ring. 0 is high and 1 is regular
>   * @mode: Doorbell mode
>   * @data_type: Type of data this ring will process
>   * @hardware_event: This ring is associated with hardware channels
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
> 

Re: [PATCH v2] bus: mhi: core: Add support for processing priority of event ring

[Manivannan Sadhasivam]

On Fri, Jun 18, 2021 at 03:05:03PM -0700, Bhaumik Bhatt wrote:
> From: Hemant Kumar <hemantk@codeaurora.org>
> 
> Event ring priorities are currently set to 1 and are unused.
> Default processing priority for event rings is set to regular
> tasklet. Controllers can choose to use high priority tasklet
> scheduling for certain event rings critical for processing such
> as ones transporting control information if they wish to avoid
> system scheduling delays for those packets. In order to support
> these use cases, allow controllers to set event ring priority to
> high.
> 
> Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>

Applied to mhi-next!

Thanks,
Mani

> ---
>  drivers/bus/mhi/core/init.c | 3 +--
>  drivers/bus/mhi/core/main.c | 9 +++++++--
>  include/linux/mhi.h         | 2 +-
>  3 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
> index c81b377..4446760 100644
> --- a/drivers/bus/mhi/core/init.c
> +++ b/drivers/bus/mhi/core/init.c
> @@ -673,8 +673,7 @@ static int parse_ev_cfg(struct mhi_controller *mhi_cntrl,
>  				&mhi_cntrl->mhi_chan[mhi_event->chan];
>  		}
>  
> -		/* Priority is fixed to 1 for now */
> -		mhi_event->priority = 1;
> +		mhi_event->priority = event_cfg->priority;
>  
>  		mhi_event->db_cfg.brstmode = event_cfg->mode;
>  		if (MHI_INVALID_BRSTMODE(mhi_event->db_cfg.brstmode))
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 8ac73f9..3775c77 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -454,10 +454,15 @@ irqreturn_t mhi_irq_handler(int irq_number, void *dev)
>  
>  		if (mhi_dev)
>  			mhi_notify(mhi_dev, MHI_CB_PENDING_DATA);
> -	} else {
> -		tasklet_schedule(&mhi_event->task);
> +
> +		return IRQ_HANDLED;
>  	}
>  
> +	if (!mhi_event->priority)
> +		tasklet_hi_schedule(&mhi_event->task);
> +	else
> +		tasklet_schedule(&mhi_event->task);
> +
>  	return IRQ_HANDLED;
>  }
>  
> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
> index 86cea52..bf23c21 100644
> --- a/include/linux/mhi.h
> +++ b/include/linux/mhi.h
> @@ -250,7 +250,7 @@ struct mhi_channel_config {
>   * @irq_moderation_ms: Delay irq for additional events to be aggregated
>   * @irq: IRQ associated with this ring
>   * @channel: Dedicated channel number. U32_MAX indicates a non-dedicated ring
> - * @priority: Priority of this ring. Use 1 for now
> + * @priority: Processing priority of this ring. 0 is high and 1 is regular
>   * @mode: Doorbell mode
>   * @data_type: Type of data this ring will process
>   * @hardware_event: This ring is associated with hardware channels
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>