linux-kernel - Re: [PATCH v7] bus: mhi: host: Add tracing support

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Date:   Thu, 7 Dec 2023 09:54:31 +0530
From:   Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To:     Steven Rostedt <rostedt@...dmis.org>
CC:     Manivannan Sadhasivam <mani@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        <linux-kernel@...r.kernel.org>, <mhi@...ts.linux.dev>,
        <linux-arm-msm@...r.kernel.org>,
        <linux-trace-kernel@...r.kernel.org>, <quic_vbadigan@...cinc.com>,
        <quic_ramkri@...cinc.com>, <quic_nitegupt@...cinc.com>,
        <quic_skananth@...cinc.com>, <quic_parass@...cinc.com>
Subject: Re: [PATCH v7] bus: mhi: host: Add tracing support


On 12/6/2023 9:25 PM, Steven Rostedt wrote:
> On Wed, 6 Dec 2023 21:12:57 +0530
> Krishna chaitanya chundru <quic_krichai@...cinc.com> wrote:
>
>> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
>> index f78aefd2d7a3..6acb85f4c5f8 100644
>> --- a/drivers/bus/mhi/host/init.c
>> +++ b/drivers/bus/mhi/host/init.c
>> @@ -20,6 +20,9 @@
>>   #include <linux/wait.h>
>>   #include "internal.h"
>>   
>> +#define CREATE_TRACE_POINTS
>> +#include "trace.h"
>> +
>>   static DEFINE_IDA(mhi_controller_ida);
>>   
>>   const char * const mhi_ee_str[MHI_EE_MAX] = {
>> diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
>> index dcf627b36e82..507cf3351a97 100644
>> --- a/drivers/bus/mhi/host/main.c
>> +++ b/drivers/bus/mhi/host/main.c
>> @@ -15,6 +15,7 @@
>>   #include <linux/skbuff.h>
>>   #include <linux/slab.h>
>>   #include "internal.h"
>> +#include "trace.h"
>>   
>>   int __must_check mhi_read_reg(struct mhi_controller *mhi_cntrl,
>>   			      void __iomem *base, u32 offset, u32 *out)
>> @@ -491,11 +492,9 @@ irqreturn_t mhi_intvec_threaded_handler(int irq_number, void *priv)
>>   
>>   	state = mhi_get_mhi_state(mhi_cntrl);
>>   	ee = mhi_get_exec_env(mhi_cntrl);
>> -	dev_dbg(dev, "local ee: %s state: %s device ee: %s state: %s\n",
>> -		TO_MHI_EXEC_STR(mhi_cntrl->ee),
>> -		mhi_state_str(mhi_cntrl->dev_state),
>> -		TO_MHI_EXEC_STR(ee), mhi_state_str(state));
>>   
>> +	trace_mhi_intvec_states(mhi_cntrl->mhi_dev->name, mhi_cntrl->ee,
>> +				mhi_cntrl->dev_state, ee, state);
> I'm not sure if this was discussed before, but why not just pass in the
> mhi_cntrl pointer and do the assigning in the TRACE_EVENT()
> TP_fast_assign() portion?
>
> It will save on setting up the parameters.
>
>>   	if (state == MHI_STATE_SYS_ERR) {
>>   		dev_dbg(dev, "System error detected\n");
>>   		pm_state = mhi_tryset_pm_state(mhi_cntrl,
>> @@ -832,6 +831,10 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
>>   	while (dev_rp != local_rp) {
>>   		enum mhi_pkt_type type = MHI_TRE_GET_EV_TYPE(local_rp);
>>   
>> +		trace_mhi_ctrl_event(mhi_cntrl->mhi_dev->name, local_rp,
>> +				     local_rp->ptr, local_rp->dword[0],
>> +				     local_rp->dword[1]);
> And here..
>
>> +
>>   		switch (type) {
>>   		case MHI_PKT_TYPE_BW_REQ_EVENT:
>>   		{
>> @@ -997,6 +1000,9 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
>>   	while (dev_rp != local_rp && event_quota > 0) {
>>   		enum mhi_pkt_type type = MHI_TRE_GET_EV_TYPE(local_rp);
>>   
>> +		trace_mhi_data_event(mhi_cntrl->mhi_dev->name, local_rp, local_rp->ptr,
>> +				     local_rp->dword[0], local_rp->dword[1]);
> and here..
>
> for the local_rp. Especially since you are just repeating what you send
> into the two events. You can consolidate it down to just adding that in the
> TP_fast_assign() of the shared DECLARE_EVENT_CLASS().
>
>> +
>>   		chan = MHI_TRE_GET_EV_CHID(local_rp);
>>   
>>   		WARN_ON(chan >= mhi_cntrl->max_chan);
>> @@ -1235,6 +1241,8 @@ int mhi_gen_tre(struct mhi_controller *mhi_cntrl, struct mhi_chan *mhi_chan,
>>   	mhi_tre->dword[0] = MHI_TRE_DATA_DWORD0(info->len);
>>   	mhi_tre->dword[1] = MHI_TRE_DATA_DWORD1(bei, eot, eob, chain);
>>   
>> +	trace_mhi_gen_tre(mhi_cntrl->mhi_dev->name, mhi_chan->chan, mhi_tre,
>> +			  mhi_tre->ptr, mhi_tre->dword[0], mhi_tre->dword[1]);
> Same here. You can pass in the mhi_tre pointer.
>
>>   	/* increment WP */
>>   	mhi_add_ring_element(mhi_cntrl, tre_ring);
>>   	mhi_add_ring_element(mhi_cntrl, buf_ring);
>> @@ -1327,9 +1335,7 @@ static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
>>   	enum mhi_cmd_type cmd = MHI_CMD_NOP;
>>   	int ret;
>>   
>> -	dev_dbg(dev, "%d: Updating channel state to: %s\n", mhi_chan->chan,
>> -		TO_CH_STATE_TYPE_STR(to_state));
>> -
>> +	trace_mhi_channel_command_start(mhi_cntrl->mhi_dev->name, mhi_chan->chan, to_state);
> And here..
>
>>   	switch (to_state) {
>>   	case MHI_CH_STATE_TYPE_RESET:
>>   		write_lock_irq(&mhi_chan->lock);
>> @@ -1396,9 +1402,7 @@ static int mhi_update_channel_state(struct mhi_controller *mhi_cntrl,
>>   		write_unlock_irq(&mhi_chan->lock);
>>   	}
>>   
>> -	dev_dbg(dev, "%d: Channel state change to %s successful\n",
>> -		mhi_chan->chan, TO_CH_STATE_TYPE_STR(to_state));
>> -
>> +	trace_mhi_channel_command_end(mhi_cntrl->mhi_dev->name, mhi_chan->chan, to_state);
> and here..
>
> Where you can also update the DECLARE_EVENT_CLASS() to directly access the
> mhi_cntrl and mhi_chan pointers. Sometimes it's better to do the
> dereference from inside the TP_fast_assign. That way, things like eprobes
> and bpf tracing can also have access to the full structure if needed.
>
> -- Steve

Hi Steve,

I will make changes as suggested in the next patch series.

- Krishna Chaitanya.