linux-kernel - Re: [PATCH v3 1/2] tpm: reduce poll sleep time in tpm

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Message-Id: <4896f0b6-70b7-77ad-1b33-f13890b6fec2@linux.vnet.ibm.com>
Date:   Mon, 14 May 2018 16:09:41 +0530
From:   Nayna Jain <nayna@...ux.vnet.ibm.com>
To:     J Freyensee <why2jjj.linux@...il.com>,
        linux-integrity@...r.kernel.org
Cc:     zohar@...ux.vnet.ibm.com, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, peterhuewe@....de,
        jarkko.sakkinen@...ux.intel.com, tpmdd@...horst.net,
        jgunthorpe@...idianresearch.com, patrickc@...ibm.com
Subject: Re: [PATCH v3 1/2] tpm: reduce poll sleep time in tpm_transmit()



On 05/10/2018 06:11 PM, Nayna Jain wrote:
>
>
> On 05/08/2018 10:04 PM, J Freyensee wrote:
>>
>>>           do {
>>> -            tpm_msleep(TPM_POLL_SLEEP);
>>> +            tpm_msleep(TPM_TIMEOUT_POLL);
>>>
>> I'm just curious why it was decided to still use tpm_msleep() here 
>> instead of usleep_range() which was used in the 2nd patch.
>
> TPM_TIMEOUT_POLL is in msec i.e. 1 msec and usleep_range() is used 
> only when timeout is needed in usecs.

Just to add bit more details:

usleep_range() is used in wait_for_tpm_stat() and get_burstcount() which 
are expected to return quickly. tpm_transmit() is a generic function 
used across all drivers and commands.
Some of the commands (eg. hash, key generation) take longer compared to 
other commands (eg. extend). The sleep time in tpm_transmit is reduced 
but kept in msecs to balance between the smaller and longer commands.

Thanks & Regards,
     - Nayna

>
>>
>> Otherwise,
>>
>> Acked-by: Jay Freyensee <why2jjj.linux@...il.com>
>
> Thanks !!
>
> Thanks & Regards,
>     - Nayna
>
>