Re: [PATCH v2] OMAP: DMA: Add API for setting channel dest addr

[Kevin Hilman <khilman@deeprootsystems.com>]

Venkatraman S <svenkatr@ti.com> writes:

> Manjunath,
>
> On Tue, Mar 2, 2010 at 7:06 PM, Manjunatha GK <manjugk@ti.com> wrote:
>> The new API - omap_set_dma_dst_pos(int lch, int value) is added
>> for setting channel destination address in CPC/CDAC register
>>
>> Cc: Tony Lindgren <tony@atomide.com>
>> Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
>> Cc: S, Venkatraman <svenkatr@ti.com>
>> Signed-off-by: Manjunatha GK <manjugk@ti.com>
>> Signed-off-by: Govindraj R <govindraj.raja@ti.com>
>> ---
>>  arch/arm/plat-omap/dma.c              |   17 +++++++++++++++++
>>  arch/arm/plat-omap/include/plat/dma.h |    1 +
>>  2 files changed, 18 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c
>> index 2ab224c..c73f11a 100644
>> --- a/arch/arm/plat-omap/dma.c
>> +++ b/arch/arm/plat-omap/dma.c
>> @@ -1109,6 +1109,23 @@ dma_addr_t omap_get_dma_dst_pos(int lch)
>>  }
>>  EXPORT_SYMBOL(omap_get_dma_dst_pos);
>>
>> +/**
>> + * omap_set_dma_dst_pos() - Set DMA channel destination address
>> + * @arg1:  lch      DMA logical channel number
>> + * @arg2:  value    Value to write into CDAC register
>> + *
>> + * Writes "value" into the register CPC/CDAC
>> + */
>> +void omap_set_dma_dst_pos(int lch, int value)
>> +{
>> +       if (cpu_is_omap15xx())
>> +               dma_write(value, CPC(lch));
>> +       else
>> +               dma_write(value, CDAC(lch));
>> +
>> +}
>> +EXPORT_SYMBOL(omap_set_dma_dst_pos);
>> +
>>  int omap_get_dma_active_status(int lch)
>>  {
>>        return (dma_read(CCR(lch)) & OMAP_DMA_CCR_EN) != 0;
>> diff --git a/arch/arm/plat-omap/include/plat/dma.h b/arch/arm/plat-omap/include/plat/dma.h
>> index 02232ca..3b6e43e 100644
>> --- a/arch/arm/plat-omap/include/plat/dma.h
>> +++ b/arch/arm/plat-omap/include/plat/dma.h
>> @@ -509,6 +509,7 @@ extern int omap_set_dma_callback(int lch,
>>                        void *data);
>>  extern dma_addr_t omap_get_dma_src_pos(int lch);
>>  extern dma_addr_t omap_get_dma_dst_pos(int lch);
>> +extern void omap_set_dma_dst_pos(int lch, int value);
>>  extern void omap_clear_dma(int lch);
>>  extern int omap_get_dma_active_status(int lch);
>>  extern int omap_dma_running(void);
>> --
>  CDAC is not the destination address, as the API seems to suggest.
> CDSA (Channel Destination Start Address) is.
>
> CDAC is a running counter of the current transfer.
> I propose to update the omap_start_dma to reset CDAC to 0 always.

I agree with Venkat.  I think having it reset for every transfer
by default is the right way to handle this.

Kevin

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