Re: [PATCH v8 1/2] sDMA: descriptor autoloading feature

[Venkatraman S <svenkatr@ti.com>]

On Wed, May 5, 2010 at 3:35 PM, Adrian Hunter <adrian.hunter@nokia.com> wrote:
> Venkatraman S wrote:
>>>
>>> From d46f8a00728cc6c1fbdfce69435759c8cc49f25c Mon Sep 17 00:00:00 2001
>>
>> From: Venkatraman S <svenkatr@ti.com>
>> Date: Thu, 29 Apr 2010 22:34:04 +0530
>> Subject: [PATCH 1/2] sDMA: descriptor autoloading feature
>>
>> Add sDMA driver support for descriptor autoloading feature.
>>  Descriptor autoloading is OMAP sDMA v5 hardware capability that can
>> be exploited for scatter gather
>>  scenarios, currently available in OMAP3630 and OMAP4430.
>>
>>  The feature works as described below.
>>  1) A sDMA channel is programmed to be in 'linked list' mode.
>>  2) The client (sDMA user) provides a list of descriptors in a linked
>> list format.
>>  3) Each of the 'descriptor' (element in the linked list) contains an
>> updated set of DMA
>>  configuration register values.
>>  4) Client starts DMA transfer.
>>  5) sDMA controller loads the first element to its register
>> configuration memory and executes the
>>  transfer.
>>  6) After completion, loads the next element (in linked list) to
>> configuration memory and executes
>>  the transfer, without MCU intervention.
>>  7) Interrupt is generated after all transfers are completed; this
>> can be configured to be done
>>  differently.
>>
>>  Configurations and additional features
>>  1) Fast mode & non-fast mode
>>        Fast mode/non-fast decides on how the first transfer begins.
>> In non-fast mode, the first
>>        element in the linked list is loaded only after completing the
>> transfer according to the
>>        configurations already in the sDMA channel registers. In fast mode,
>> the loading of the first
>>        element precedes the transfer.
>>
>>  2) Pause / resume of transfers
>>        A transfer can be paused after a descriptor set has been loaded,
>> provided the 'pause
>>        bit' is set in the linked list element.
>>        An ongoing transfer cannot be paused. If the 'pause bit' is set,
>> transfer is not
>>        started after loading the register set from memory.
>>        Such a transfer can be resumed later.
>>
>>  3) Descriptor types
>>        3 possible configurations of descriptors (initialized as linked
>> list elements)
>>        are possible. Type 1 provides the maximum flexibility, which
>> contains most
>>        register definitions of a DMA logical channel. Fewer options are
>> present in type
>>        2. Type 3 can just modify source/destinations address of transfers.
>> In all
>>        transfers, unmodified registers settings are maintained for the
>> next transfer.
>>
>>        Patch provides options / API for
>>            1) Setting up a descriptor loading for DMA channel for sg type
>> transfers
>>            2) configuration with linked list elements
>>            3) Starting / pause and resume of the said transfers, query
>> state
>>            4) Clearing the sglist mode
>>
>> Signed-off-by: Venkatraman S <svenkatr@ti.com>
>> CC: Adrian Hunter <adrian.hunter@nokia.com>
>> CC: Madhusudhan C <madhu.cr@ti.com>
>> CC: Shilimkar Santosh <santosh.shilimkar@ti.com>
>> CC: Tony Lindgren <tony@atomide.com>
>> ---
>>  Changes from v7:
>>   * Added wmb() calls between descriptor data structure update and
>> start/resume of transfer
>>   * Added proper commit log about the feature
>>
>>  arch/arm/plat-omap/dma.c              |  289
>> ++++++++++++++++++++++++++++++++-
>>  arch/arm/plat-omap/include/plat/dma.h |  170 +++++++++++++++++++
>>  2 files changed, 458 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c
>> index f6c9bdc..d8d4df8 100644
>> --- a/arch/arm/plat-omap/dma.c
>> +++ b/arch/arm/plat-omap/dma.c
>> @@ -46,12 +46,40 @@ enum { DMA_CH_ALLOC_DONE, DMA_CH_PARAMS_SET_DONE,
>> DMA_CH_STARTED,
>>  enum { DMA_CHAIN_STARTED, DMA_CHAIN_NOTSTARTED };
>>  #endif
>>
>> +/* CDP Register bitmaps */
>> +#define DMA_LIST_CDP_DST_VALID (BIT(0))
>> +#define DMA_LIST_CDP_SRC_VALID (BIT(2))
>> +#define DMA_LIST_CDP_TYPE1     (BIT(4))
>> +#define DMA_LIST_CDP_TYPE2     (BIT(5))
>> +#define DMA_LIST_CDP_TYPE3     (BIT(4) | BIT(5))
>> +#define DMA_LIST_CDP_PAUSEMODE (BIT(7))
>> +#define DMA_LIST_CDP_LISTMODE  (BIT(8))
>> +#define DMA_LIST_CDP_FASTMODE  (BIT(10))
>> +/* CAPS register bitmaps */
>> +#define DMA_CAPS_SGLIST_SUPPORT        (BIT(20))
>> +
>> +#define DMA_LIST_DESC_PAUSE    (BIT(0))
>> +#define DMA_LIST_DESC_SRC_VALID        (BIT(24))
>> +#define DMA_LIST_DESC_DST_VALID        (BIT(26))
>> +#define DMA_LIST_DESC_BLK_END  (BIT(28))
>> +
>
> The () are not needed around BIT()
OK

>
>>  #define OMAP_DMA_ACTIVE                        0x01
>>  #define OMAP2_DMA_CSR_CLEAR_MASK       0xffe
>>
>>  #define OMAP_FUNC_MUX_ARM_BASE         (0xfffe1000 + 0xec)
>> +#define OMAP_DMA_INVALID_FRAME_COUNT   (0xffff)
>> +#define OMAP_DMA_INVALID_ELEM_COUNT    (0xffffff)
>> +#define OMAP_DMA_INVALID_DESCRIPTOR_POINTER    (0xfffffffc)
>
> The () are not needed around literals
>
OK

>>
>>  static int enable_1510_mode;
>> +static int dma_caps0_status;
>> +