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Date:   Fri, 16 Jul 2021 11:22:37 -0700
From:   Bhaumik Bhatt <bbhatt@codeaurora.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        kvalo@codeaurora.org
Cc:     linux-arm-msm@vger.kernel.org, hemantk@codeaurora.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] bus: mhi: core: Add support for processing priority of
 event ring
Organization: Qualcomm Innovation Center, Inc.
Reply-To: bbhatt@codeaurora.org
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In-Reply-To: <20210716114926.GH3323@workstation>
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 <20210716114926.GH3323@workstation>
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Hi Mani,

On 2021-07-16 04:49 AM, Manivannan Sadhasivam wrote:
> On Fri, Jun 25, 2021 at 10:22:08AM -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.
>> 
> 
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> 
> Just curious, what are the event rings you are going to make as high
> priority? If you are going to do that for existing controllers, please
> submit a patch now itself.
> 
> Thanks,
> Mani
> 
Idea for this patch came from 914b72a6948b ("bus: mhi: Wait for M2 state 
during system resume").

If WLAN ath11k controller driver wants to avoid the scenario mentioned 
in
the above patch, it will help them to have a high priority for their 
dedicated
control events ring.

I would defer to Kalle and others in ath11k, whether or not they are OK 
to take that route.
as an update to priority will just help return from resume faster.
It will also depend on system load/reproducibility rate of the scenario.

I can provide a patch for them to review/test since I do not have the 
setup for it.

>> Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
>> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
>> ---
>> v5:
>> -Add controller changes and enable usage of event ring configuration 
>> priorities
>> -Fix nitpick, use high instead of hi in kdoc
>> 
>> v4:
>> -Update fixed priority for all events to default to fix bug in v3
>> -Supply changelog
>> 
>> v3:
>> -Revert to enum approach
>> -Use 0 as default and 1 as high in enum
>> -Do not use config values for event rings
>> 
>> v2:
>> -Use boolean approach for easy maintenance as controllers do not need 
>> updates
>> 
>> 
>> 
>>  drivers/bus/mhi/core/init.c           |  3 +-
>>  drivers/bus/mhi/core/internal.h       |  2 +-
>>  drivers/bus/mhi/core/main.c           | 19 ++++++++--
>>  drivers/bus/mhi/pci_generic.c         | 66 
>> +++++++++++++++++------------------
>>  drivers/net/wireless/ath/ath11k/mhi.c |  4 +--
>>  include/linux/mhi.h                   | 14 ++++++--
>>  6 files changed, 65 insertions(+), 43 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/internal.h 
>> b/drivers/bus/mhi/core/internal.h
>> index 672052f..666e102 100644
>> --- a/drivers/bus/mhi/core/internal.h
>> +++ b/drivers/bus/mhi/core/internal.h
>> @@ -535,7 +535,7 @@ struct mhi_event {
>>  	u32 intmod;
>>  	u32 irq;
>>  	int chan; /* this event ring is dedicated to a channel (optional) */
>> -	u32 priority;
>> +	enum mhi_er_priority priority;
>>  	enum mhi_er_data_type data_type;
>>  	struct mhi_ring ring;
>>  	struct db_cfg db_cfg;
>> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
>> index 8ac73f9..bfc9776 100644
>> --- a/drivers/bus/mhi/core/main.c
>> +++ b/drivers/bus/mhi/core/main.c
>> @@ -425,10 +425,11 @@ void mhi_create_devices(struct mhi_controller 
>> *mhi_cntrl)
>>  	}
>>  }
>> 
>> -irqreturn_t mhi_irq_handler(int irq_number, void *dev)
>> +irqreturn_t mhi_irq_handler(int irq_number, void *priv)
>>  {
>> -	struct mhi_event *mhi_event = dev;
>> +	struct mhi_event *mhi_event = priv;
>>  	struct mhi_controller *mhi_cntrl = mhi_event->mhi_cntrl;
>> +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>>  	struct mhi_event_ctxt *er_ctxt =
>>  		&mhi_cntrl->mhi_ctxt->er_ctxt[mhi_event->er_index];
>>  	struct mhi_ring *ev_ring = &mhi_event->ring;
>> @@ -454,8 +455,20 @@ irqreturn_t mhi_irq_handler(int irq_number, void 
>> *dev)
>> 
>>  		if (mhi_dev)
>>  			mhi_notify(mhi_dev, MHI_CB_PENDING_DATA);
>> -	} else {
>> +
>> +		return IRQ_HANDLED;
>> +	}
>> +
>> +	switch (mhi_event->priority) {
>> +	case MHI_ER_PRIORITY_HI:
>> +		tasklet_hi_schedule(&mhi_event->task);
>> +		break;
>> +	case MHI_ER_PRIORITY_DEFAULT:
>>  		tasklet_schedule(&mhi_event->task);
>> +		break;
>> +	default:
>> +		dev_err(dev, "Skip event of unknown priority\n");
>> +		break;
>>  	}
>> 
>>  	return IRQ_HANDLED;
>> diff --git a/drivers/bus/mhi/pci_generic.c 
>> b/drivers/bus/mhi/pci_generic.c
>> index 31360a2..5886547 100644
>> --- a/drivers/bus/mhi/pci_generic.c
>> +++ b/drivers/bus/mhi/pci_generic.c
>> @@ -74,17 +74,17 @@ struct mhi_pci_dev_info {
>>  		.doorbell_mode_switch = false,		\
>>  	}
>> 
>> -#define MHI_EVENT_CONFIG_CTRL(ev_ring, el_count) \
>> -	{					\
>> -		.num_elements = el_count,	\
>> -		.irq_moderation_ms = 0,		\
>> -		.irq = (ev_ring) + 1,		\
>> -		.priority = 1,			\
>> -		.mode = MHI_DB_BRST_DISABLE,	\
>> -		.data_type = MHI_ER_CTRL,	\
>> -		.hardware_event = false,	\
>> -		.client_managed = false,	\
>> -		.offload_channel = false,	\
>> +#define MHI_EVENT_CONFIG_CTRL(ev_ring, el_count)	\
>> +	{						\
>> +		.num_elements = el_count,		\
>> +		.irq_moderation_ms = 0,			\
>> +		.irq = (ev_ring) + 1,			\
>> +		.priority = MHI_ER_PRIORITY_DEFAULT,	\
>> +		.mode = MHI_DB_BRST_DISABLE,		\
>> +		.data_type = MHI_ER_CTRL,		\
>> +		.hardware_event = false,		\
>> +		.client_managed = false,		\
>> +		.offload_channel = false,		\
>>  	}
>> 
>>  #define MHI_CHANNEL_CONFIG_HW_UL(ch_num, ch_name, el_count, ev_ring) 
>> \
>> @@ -177,31 +177,31 @@ struct mhi_pci_dev_info {
>>  		.doorbell_mode_switch = false,		\
>>  	}
>> 
>> -#define MHI_EVENT_CONFIG_DATA(ev_ring, el_count) \
>> -	{					\
>> -		.num_elements = el_count,	\
>> -		.irq_moderation_ms = 5,		\
>> -		.irq = (ev_ring) + 1,		\
>> -		.priority = 1,			\
>> -		.mode = MHI_DB_BRST_DISABLE,	\
>> -		.data_type = MHI_ER_DATA,	\
>> -		.hardware_event = false,	\
>> -		.client_managed = false,	\
>> -		.offload_channel = false,	\
>> +#define MHI_EVENT_CONFIG_DATA(ev_ring, el_count)	\
>> +	{						\
>> +		.num_elements = el_count,		\
>> +		.irq_moderation_ms = 5,			\
>> +		.irq = (ev_ring) + 1,			\
>> +		.priority = MHI_ER_PRIORITY_DEFAULT,	\
>> +		.mode = MHI_DB_BRST_DISABLE,		\
>> +		.data_type = MHI_ER_DATA,		\
>> +		.hardware_event = false,		\
>> +		.client_managed = false,		\
>> +		.offload_channel = false,		\
>>  	}
>> 
>>  #define MHI_EVENT_CONFIG_HW_DATA(ev_ring, el_count, ch_num) \
>> -	{					\
>> -		.num_elements = el_count,	\
>> -		.irq_moderation_ms = 1,		\
>> -		.irq = (ev_ring) + 1,		\
>> -		.priority = 1,			\
>> -		.mode = MHI_DB_BRST_DISABLE,	\
>> -		.data_type = MHI_ER_DATA,	\
>> -		.hardware_event = true,		\
>> -		.client_managed = false,	\
>> -		.offload_channel = false,	\
>> -		.channel = ch_num,		\
>> +	{						\
>> +		.num_elements = el_count,		\
>> +		.irq_moderation_ms = 1,			\
>> +		.irq = (ev_ring) + 1,			\
>> +		.priority = MHI_ER_PRIORITY_DEFAULT,	\
>> +		.mode = MHI_DB_BRST_DISABLE,		\
>> +		.data_type = MHI_ER_DATA,		\
>> +		.hardware_event = true,			\
>> +		.client_managed = false,		\
>> +		.offload_channel = false,		\
>> +		.channel = ch_num,			\
>>  	}
>> 
>>  static const struct mhi_channel_config modem_qcom_v1_mhi_channels[] = 
>> {
>> diff --git a/drivers/net/wireless/ath/ath11k/mhi.c 
>> b/drivers/net/wireless/ath/ath11k/mhi.c
>> index 27b394d..b7864fc 100644
>> --- a/drivers/net/wireless/ath/ath11k/mhi.c
>> +++ b/drivers/net/wireless/ath/ath11k/mhi.c
>> @@ -86,7 +86,7 @@ static struct mhi_event_config 
>> ath11k_mhi_events_qca6390[] = {
>>  		.irq_moderation_ms = 1,
>>  		.irq = 2,
>>  		.mode = MHI_DB_BRST_DISABLE,
>> -		.priority = 1,
>> +		.priority = MHI_ER_PRIORITY_DEFAULT,
>>  		.hardware_event = false,
>>  		.client_managed = false,
>>  		.offload_channel = false,
>> @@ -179,7 +179,7 @@ static struct mhi_event_config 
>> ath11k_mhi_events_qcn9074[] = {
>>  		.irq_moderation_ms = 1,
>>  		.irq = 2,
>>  		.mode = MHI_DB_BRST_DISABLE,
>> -		.priority = 1,
>> +		.priority = MHI_ER_PRIORITY_DEFAULT,
>>  		.hardware_event = false,
>>  		.client_managed = false,
>>  		.offload_channel = false,
>> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
>> index 86cea52..3e92e85 100644
>> --- a/include/linux/mhi.h
>> +++ b/include/linux/mhi.h
>> @@ -198,6 +198,16 @@ enum mhi_er_data_type {
>>  };
>> 
>>  /**
>> + * enum mhi_er_priority - Event ring processing priority
>> + * @MHI_ER_PRIORITY_DEFAULT: processed by regular tasklet
>> + * @MHI_ER_PRIORITY_HI: processed by high priority tasklet
>> + */
>> +enum mhi_er_priority {
>> +	MHI_ER_PRIORITY_DEFAULT,
>> +	MHI_ER_PRIORITY_HI,
>> +};
>> +
>> +/**
>>   * enum mhi_db_brst_mode - Doorbell mode
>>   * @MHI_DB_BRST_DISABLE: Burst mode disable
>>   * @MHI_DB_BRST_ENABLE: Burst mode enable
>> @@ -250,7 +260,7 @@ 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.
>>   * @mode: Doorbell mode
>>   * @data_type: Type of data this ring will process
>>   * @hardware_event: This ring is associated with hardware channels
>> @@ -262,7 +272,7 @@ struct mhi_event_config {
>>  	u32 irq_moderation_ms;
>>  	u32 irq;
>>  	u32 channel;
>> -	u32 priority;
>> +	enum mhi_er_priority priority;
>>  	enum mhi_db_brst_mode mode;
>>  	enum mhi_er_data_type data_type;
>>  	bool hardware_event;
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
>> 

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