On Wed, Sep 25, 2013 at 7:17 PM, Akinobu Mita <mita@xxxxxxxxxxxx> wrote:
> The data byte count field of PRDT indicates the length of data block
> which is a segment of data transfer for SCSI commands. The value of
> this field shall have Dword granularity and the the maximum of length
> is 256KB.
>
> This adjusts dma pad mask and max segment size to the above-mentioned
> PRDT limitations.
>
> Signed-off-by: Akinobu Mita <mita@xxxxxxxxxxxx>
> Cc: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
> Cc: Vinayak Holikatti <vinholikatti@xxxxxxxxx>
> Cc: Santosh Y <santoshsy@xxxxxxxxx>
> Cc: "James E.J. Bottomley" <JBottomley@xxxxxxxxxxxxx>
> Cc: linux-scsi@xxxxxxxxxxxxxxx
> ---
> * Change from v1
> - Add comments for PRDT limitations as suggested by Subhash Jadavani
>
> drivers/scsi/ufs/ufshcd.c | 15 +++++++++++++++
> drivers/scsi/ufs/ufshci.h | 5 +++++
> 2 files changed, 20 insertions(+)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index a2abe9a..660792e 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1918,6 +1918,20 @@ static int ufshcd_slave_alloc(struct scsi_device *sdev)
> }
>
> /**
> + * ufshcd_slave_configure - adjust SCSI device configurations
> + * @sdev: pointer to SCSI device
> + */
> +static int ufshcd_slave_configure(struct scsi_device *sdev)
> +{
> + struct request_queue *q = sdev->request_queue;
> +
> + blk_queue_update_dma_pad(q, PRDT_DATA_BYTE_COUNT_PAD - 1);
> + blk_queue_max_segment_size(q, PRDT_DATA_BYTE_COUNT_MAX);
> +
> + return 0;
> +}
> +
> +/**
> * ufshcd_slave_destroy - remove SCSI device configurations
> * @sdev: pointer to SCSI device
> */
> @@ -2748,6 +2762,7 @@ static struct scsi_host_template ufshcd_driver_template = {
> .proc_name = UFSHCD,
> .queuecommand = ufshcd_queuecommand,
> .slave_alloc = ufshcd_slave_alloc,
> + .slave_configure = ufshcd_slave_configure,
> .slave_destroy = ufshcd_slave_destroy,
> .eh_abort_handler = ufshcd_abort,
> .eh_device_reset_handler = ufshcd_device_reset,
> diff --git a/drivers/scsi/ufs/ufshci.h b/drivers/scsi/ufs/ufshci.h
> index 0475c66..b2b7004 100644
> --- a/drivers/scsi/ufs/ufshci.h
> +++ b/drivers/scsi/ufs/ufshci.h
> @@ -296,6 +296,11 @@ enum {
> MASK_OCS = 0x0F,
> };
>
> +/* The maximum length of the data byte count field in the PRDT is 256KB */
> +#define PRDT_DATA_BYTE_COUNT_MAX (256 * 1024)
> +/* The granularity of the data byte count field in the PRDT is 32-bit */
> +#define PRDT_DATA_BYTE_COUNT_PAD 4
> +
> /**
> * struct ufshcd_sg_entry - UFSHCI PRD Entry
> * @base_addr: Lower 32bit physical address DW-0
Acked-by: Vinayak Holikatti <vinholikatti@xxxxxxxxx>
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