Re: [PATCH v2 0/2] Add Qualcomm MSM ADM DMAEngine driver

From: Ravi Kumar V
Date: Fri Jan 20 2012 - 07:30:33 EST

On 1/17/2012 7:15 PM, Vinod Koul wrote:
On Fri, 2012-01-06 at 18:17 +0530, Ravi Kumar V wrote:
<sorry for delayed review, was on vacation and now traveling>

As our ADM Scatter-gather hardware needs
-32-bit command configuration parameter
apart from
-32-bit source address
-32-bit destination address
-16-bit length

So,we have added new parameter in struct scatterlist to support xfer
descriptor
specific private data, and for supporting ADM Box mode DMA we added
new
API and data structure.
what do you mean by "ADM Box mode"?


ADM Box mode is a interleaved type of DMA where data from rows of equal length and equal distance(bytes) between each other are transferred to similar pattern of rows.
Each row length and distance between each row in destination pattern may not be equal to source pattern.
Distance between beginning of any two rows are always greater than row length.
Example:
If 4 rows of 16 bytes each are arranged such that distance between beginning of any two rows are 32 bytes.
Now they can be transferred using BOX mode to destination pattern arranged in 2 rows of 32 bytes each and distance between them can be any lets say 128 bytes.

Source pattern:
4 data rows starts address 0th byte.

0-----16-bytes-data-----15
16 16 bytes void 31
32---------data---------47
48 void 63
64---------data---------79
80 void 95
96---------data--------111

Transferred to destination
Destination pattern:
2 rows
0----------32-bytes-data----------31
32 96 bytes void 127
128-------------data-------------159

--
Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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