linux-kernel - Re: [PATCH v3 6/7] venus: Make debug infrastructure more flexible

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Date:   Wed, 10 Jun 2020 16:29:27 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-acpi@...r.kernel.org,
        netdev@...r.kernel.org, Joe Perches <joe@...ches.com>,
        Jason Baron <jbaron@...mai.com>
Subject: Re: [PATCH v3 6/7] venus: Make debug infrastructure more flexible



On 6/9/20 2:14 PM, Greg Kroah-Hartman wrote:
> On Tue, Jun 09, 2020 at 01:46:03PM +0300, Stanimir Varbanov wrote:
>> Here we introduce few debug macros with levels (low, medium and
>> high) and debug macro for firmware. Enabling the particular level
>> will be done by dynamic debug with levels.
>>
>> For example to enable debug messages with low level:
>> echo 'module venus_dec level 0x01 +p' > debugfs/dynamic_debug/control
>>
>> If you want to enable all levels:
>> echo 'module venus_dec level 0x07 +p' > debugfs/dynamic_debug/control
>>
>> All the features which dynamic debugging provide are preserved.
>>
>> And finaly all dev_dbg are translated to VDBGX with appropriate
>> debug levels.
>>
>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
>> ---
>>  drivers/media/platform/qcom/venus/core.h      |  5 ++
>>  drivers/media/platform/qcom/venus/helpers.c   |  2 +-
>>  drivers/media/platform/qcom/venus/hfi_msgs.c  | 30 ++++-----
>>  drivers/media/platform/qcom/venus/hfi_venus.c | 20 ++++--
>>  .../media/platform/qcom/venus/pm_helpers.c    |  3 +-
>>  drivers/media/platform/qcom/venus/vdec.c      | 63 +++++++++++++++++--
>>  drivers/media/platform/qcom/venus/venc.c      |  4 ++
>>  7 files changed, 96 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/media/platform/qcom/venus/core.h b/drivers/media/platform/qcom/venus/core.h
>> index b48782f9aa95..63eabf5ff96d 100644
>> --- a/drivers/media/platform/qcom/venus/core.h
>> +++ b/drivers/media/platform/qcom/venus/core.h
>> @@ -15,6 +15,11 @@
>>  #include "dbgfs.h"
>>  #include "hfi.h"
>>  
>> +#define VDBGL(fmt, args...)	pr_debug_level(0x01, fmt, ##args)
>> +#define VDBGM(fmt, args...)	pr_debug_level(0x02, fmt, ##args)
>> +#define VDBGH(fmt, args...)	pr_debug_level(0x04, fmt, ##args)
>> +#define VDBGFW(fmt, args...)	pr_debug_level(0x08, fmt, ##args)
>> +
>>  #define VIDC_CLKS_NUM_MAX		4
>>  #define VIDC_VCODEC_CLKS_NUM_MAX	2
>>  #define VIDC_PMDOMAINS_NUM_MAX		3
>> diff --git a/drivers/media/platform/qcom/venus/helpers.c b/drivers/media/platform/qcom/venus/helpers.c
>> index 0143af7822b2..115a9a2af1d6 100644
>> --- a/drivers/media/platform/qcom/venus/helpers.c
>> +++ b/drivers/media/platform/qcom/venus/helpers.c
>> @@ -396,7 +396,7 @@ put_ts_metadata(struct venus_inst *inst, struct vb2_v4l2_buffer *vbuf)
>>  	}
>>  
>>  	if (slot == -1) {
>> -		dev_dbg(inst->core->dev, "%s: no free slot\n", __func__);
>> +		VDBGH("no free slot for timestamp\n");
> 
> So you just lost the information that dev_dbg() gave you with regards to
> the device/driver/instance creating that message?

No, I don't lose anything.  When I do debug I know that all debug
messages comes from my driver.  dev_dbg will give me few device
identifiers which I don't care so much. IMO, the device information
makes more sense to dev_err/warn/err variants.  On the other side we
will have dev_dbg_level(group) if still someone needs the device
information.

> 
> Ick, no, don't do that.
> 
> And why is this driver somehow "special" compared to all the rest of

Of course it is special ... to me ;-)

> the kernel?  Why is the current dev_dbg() control not sufficient that
> you need to change the core for just this tiny thing?
> 
> thanks,
> 
> greg k-h
> 

-- 
regards,
Stan