linux-kernel - Re: [PATCHv12 7/9] asm-generic/io: Add logging support for MMIO accessors

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Message-ID: <6688ffa2-ec14-9126-1296-6180bab3e1d6@quicinc.com>
Date:   Thu, 28 Apr 2022 16:51:49 +0530
From:   Sai Prakash Ranjan <quic_saipraka@...cinc.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     <arnd@...db.de>, <catalin.marinas@....com>, <rostedt@...dmis.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <maz@...nel.org>, <quic_psodagud@...cinc.com>,
        <quic_tsoni@...cinc.com>, <will@...nel.org>
Subject: Re: [PATCHv12 7/9] asm-generic/io: Add logging support for MMIO
 accessors

On 4/28/2022 4:21 PM, Greg KH wrote:
> On Thu, Apr 28, 2022 at 03:25:30PM +0530, Sai Prakash Ranjan wrote:
>> Add logging support for MMIO high level accessors such as read{b,w,l,q}
>> and their relaxed versions to aid in debugging unexpected crashes/hangs
>> caused by the corresponding MMIO operation.
>>
>> Signed-off-by: Sai Prakash Ranjan <quic_saipraka@...cinc.com>
>> ---
>>   include/asm-generic/io.h | 82 ++++++++++++++++++++++++++++++++++++++--
>>   1 file changed, 78 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
>> index 7ce93aaf69f8..99090722cb4b 100644
>> --- a/include/asm-generic/io.h
>> +++ b/include/asm-generic/io.h
>> @@ -10,6 +10,7 @@
>>   #include <asm/page.h> /* I/O is all done through memory accesses */
>>   #include <linux/string.h> /* for memset() and memcpy() */
>>   #include <linux/types.h>
>> +#include <linux/instruction_pointer.h>
>>   
>>   #ifdef CONFIG_GENERIC_IOMAP
>>   #include <asm-generic/iomap.h>
>> @@ -61,6 +62,35 @@
>>   #define __io_par(v)     __io_ar(v)
>>   #endif
>>   
>> +#if IS_ENABLED(CONFIG_TRACE_MMIO_ACCESS) && !(defined(__DISABLE_TRACE_MMIO__))
> Shouldn't you document __DISABLE_TRACE_MMIO__ somewhere?  It's not even
> in the changelog.  Put a big comment above this for what is is for and
> how to use it.  Otherwise you will forget all about this in 6 months :)
>
> thanks,
>
> greg k-h

Didn't you ask me to split the patch to the one actually adding the flag and the one using it.
So I have added the description in that patch which adds the flag since we can't add description
everywhere we use the flag right :)

Thanks,
Sai