linux-kernel - Re: [PATCH v3 2/5] [SCSI] ufshcd: UFS UTP Transfer requests handling

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Message-ID: <CALMYJDvvY_7FpiVGuguK8i1C_n9ogJhrgsH+KerDc62Omn35aA@mail.gmail.com>
Date:	Tue, 27 Mar 2012 11:22:45 +0530
From:	Santosh Y <santoshsy@...il.com>
To:	KOBAYASHI Yoshitake <yoshitake.kobayashi@...hiba.co.jp>
Cc:	James Bottomley <James.Bottomley@...senpartnership.com>,
	linux-scsi@...r.kernel.org, patches@...aro.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	arnd.bergmann@...aro.org, saugata.das@...aro.org,
	dsaxena@...aro.org, stephen.doel@...aro.org, venkat@...aro.org,
	ilho215.lee@...sung.com, nala.la@...sung.com,
	girish.shivananjappa@...aro.org, vishak.g@...sung.com,
	k.rajesh@...sung.com, yejin.moon@...sung.com,
	sreekumar.c@...sung.com, vinholikatti@...il.com,
	linkinjeon@...il.com, michaelc@...wisc.edu
Subject: Re: [PATCH v3 2/5] [SCSI] ufshcd: UFS UTP Transfer requests handling

On Mon, Mar 26, 2012 at 10:04 AM, KOBAYASHI Yoshitake
<yoshitake.kobayashi@...hiba.co.jp> wrote:
> Santosh Y wrote:
>>
>> +        ucd_cmd_ptr->exp_data_transfer_len =
>> +            cpu_to_be32(lrbp->cmd->transfersize);
>> +
>> +        memcpy(ucd_cmd_ptr->cdb,
>> +               lrbp->cmd->cmnd,
>> +               (min_t(unsigned short,
>> +                  lrbp->cmd->cmd_len,
>> +                  MAX_CDB_SIZE)));
>
>
> "Exptected Data Transfer Length" field contains a value that
> represents the number of bytes that are required to complete the
> SCSI command request and the number of bytes that the Initiator
> expects to be transferred to/from the Target.
> (JEDEC Standard 220 Table7-7)
> On the other hand, "transfersize" in a scsi_cmnd struct is trimmed
> to the sector size when requested transfer length exceeds it.
> You may derive the actual transfer length from SCSI command itself like
> following.
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index feffe65..e63fecb 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -647,6 +647,34 @@ static void ufshcd_compose_upiu(struct ufshcd_lrb
> *lrbp)
>                       (min_t(unsigned short,
>                              lrbp->cmd->cmd_len,
>                              MAX_CDB_SIZE)));
> +
> +               /* Overwrite exptected transfer length by using
> TRANSFER_LENGTH in SCSI commands */
> +               switch(ucd_cmd_ptr->cdb[0]) {
> +               case READ_6:
> +               case WRITE_6:
> +                       ucd_cmd_ptr->exp_data_transfer_len =
> +                               cpu_to_be32(lrbp->cmd->transfersize *
> +                                           ucd_cmd_ptr->cdb[4]);
> +                       break;
> +               case READ_10:
> +               case WRITE_10:
> +                       ucd_cmd_ptr->exp_data_transfer_len =
> +                               cpu_to_be32(lrbp->cmd->transfersize *
> +                                           ((ucd_cmd_ptr->cdb[7] << 8) |
> +                                            ucd_cmd_ptr->cdb[8]));
> +                       break;
> +               case READ_12:
> +               case WRITE_12:

Just a minor change, this will be READ_16 and WRITE_16.

> +                       ucd_cmd_ptr->exp_data_transfer_len =
> +                               cpu_to_be32(lrbp->cmd->transfersize *
> +                                           ((ucd_cmd_ptr->cdb[10] << 24) |
> +                                            (ucd_cmd_ptr->cdb[11] << 16) |
> +                                            (ucd_cmd_ptr->cdb[12] << 8) |
> +                                            ucd_cmd_ptr->cdb[13]));
> +                       break;
> +               default:
> +                       break;
> +               }
>                break;
>        case UTP_CMD_TYPE_DEV_MANAGE:
>
>                /* For query function implementation */
>

-- 
~Santosh
--
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