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Subject: Re: [PATCH v2 1/5] scsi: Adjust DBD setting in mode sense for caching
 mode page per LLD
From:   Mark Salyzyn <salyzyn@android.com>
To:     Can Guo <cang@codeaurora.org>, asutoshd@codeaurora.org,
        nguyenb@codeaurora.org, rnayak@codeaurora.org,
        linux-scsi@vger.kernel.org, kernel-team@android.com,
        saravanak@google.com, salyzyn@google.com
Cc:     "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        open list <linux-kernel@vger.kernel.org>
References: <1572318655-28772-1-git-send-email-cang@codeaurora.org>
 <1572318655-28772-2-git-send-email-cang@codeaurora.org>
 <fd78538f-8e5f-2e5f-0107-a8bc284d037d@android.com>
Message-ID: <6bda63c6-4bcf-b7ad-f552-4c72ba0b9024@android.com>
Date:   Thu, 31 Oct 2019 08:40:21 -0700
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On 10/31/19 8:20 AM, Mark Salyzyn wrote:
> On 10/28/19 8:10 PM, Can Guo wrote:
>> Host sends MODE_SENSE_10 with caching mode page, to check if the device
>> supports the cache feature.
>> UFS JEDEC standards require DBD field to be set to 1.
>>
>> This patch allows LLD to define the setting of DBD if required.
>>
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> ---
>>   drivers/scsi/sd.c        | 6 +++++-
>>   include/scsi/scsi_host.h | 6 ++++++
>>   2 files changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
>> index aab4ed8..6d8194f 100644
>> --- a/drivers/scsi/sd.c
>> +++ b/drivers/scsi/sd.c
>> @@ -2629,6 +2629,7 @@ static int sd_try_rc16_first(struct scsi_device 
>> *sdp)
>>   {
>>       int len = 0, res;
>>       struct scsi_device *sdp = sdkp->device;
>> +    struct Scsi_Host *host = sdp->host;
> variable locality
>>       int dbd;
>>       int modepage;
>> @@ -2660,7 +2661,10 @@ static int sd_try_rc16_first(struct 
>> scsi_device *sdp)
>>           dbd = 8;
>>       } else {
>>           modepage = 8;
>> -        dbd = 0;
>> +        if (host->set_dbd_for_caching)
>> +            dbd = 8;
>> +        else
>> +            dbd = 0;
>>       }
>
> This simplifies to:
>
> -   } else if (sdp->type == TYPE_RBC) {
>
> +    } else if (sdp->type == TYPE_RBC || sdp->host->set_dbd_for_caching) {

IDK what happened with my mailer sending out an older infant copy (blame 
on fumble fingers). My final copy was instead the simplification:

+    dbd = sdp->host->set_dbd_for_caching ? 8 : 0;