Hi Joe,
joe joe wrote
>
> I'm having an issue trying to do a synchronous multiple (burst) read (4,
> 8, 16 Word16) with the sDMA.
> Currently, it seems like my sDMA is requesting the data from the GPMC as
> single word reads. I believe I have the GPMC configured properly for
> burst reads since I am able to perform a 4 word burst with the following
> non-DMA method.
>
> volatile u64 *ptr = gpmc_cs_phys_base;
> u64 return_data;
> return_data = *ptr;
>
> Looks like the method above forces the system to request the 64bits from
> the GPMC causing it to do a 4 word burst, while the DMA evidently does not
> do this. So, how do I get the system DMA to request 64, 128, and 256 bits
> at a time for 4, 8, and 16 word bursts, respectively?
>
> When I attempt to use DMA for a 4 word burst read, I get 4 independent CS
> assertions and 1 word read for each CS assertion, I was instead expecting
> a burst (one CS assertion with 4 read words since my FPGA device is
> writing 4 words per CS assertion).
>
> For what its worth, I was able to use the sDMA to perform RAM to RAM data
> transfer, so that tells me that my DMA configuration is not completely
> hosed. Is there anything else I have to take into consideration for
> performing 64, 128, 256 word reads with the DMA to trigger a GPMC burst?
>
I'm also trying to find the proper Linux C-functions to do burst read/write
for the GPMC too, first non-DMA and then with DMA.
Can you advise me what are the functions call to do that? I only managed to
do 1 word read/write request using readw() and writew().
I do not get what you means with the 3 non-DMA instructions.
joe joe wrote
>
> I believe I have the GPMC configured properly for burst reads since I am
> able to perform a 4 word burst with the following non-DMA method.
>
> volatile u64 *ptr = gpmc_cs_phys_base;
> u64 return_data;
> return_data = *ptr;
>
> Looks like the method above forces the system to request the 64bits from
> the GPMC causing it to do a 4 word burst
>
Can you advise?
Many thanks in adv.
James Ang.
--
View this message in context: http://gumstix.8.n6.nabble.com/OMAP-3530-GPMC-burst-reads-with-sDMA-tp574833p4951792.html
Sent from the Gumstix mailing list archive at Nabble.com.
|