Re: [ts-7000] Re: DMA with SSP on TS7400

["Breton M. Saunders" <>]

The symptoms you describe are likely caused by data not being flushed to 
physical ram prior to invoking your dma transfer.

Just checking back to the sdcard driver I did for the 7400. I did:

dmac_flush_range(buf,buf+buflen); // where buf is a pointer to a virtual 
address (e.g. not a bus address)

prior to performing a dma transfer.

Although not strictly necessary on this platform, you should probably 
make sure you use the GFP_DMA flag when you allocate memory for your 
buffers.

Incidentally, you are running this on a >2.6.27 platform?
Also, you aren't using the sdcard driver in dma mode right? There will 
be some pretty serious problems if you are using TS's driver and just 
banging commands directly into the M2M registers.

I think at 6k bytes per second you might as well not bother with DMA. 
 From memory, 6k transfers at half fifo size (4 bytes) per interrupt is 
1500 interrupts per second. Keeping the ISR time short, you'll hardly 
notice a performance drop. The main issue, though, is what are the 
peripherals you are addressing? If your peripheral is something like a 
tmp127, then the amount of signaling needed will kill any advantage of a 
dma driver. If you're transferring from a memory chip, then dma is 
probably quite sensible.

-bms

pakorn_0608 wrote:
> Unfortunately for me,I test it more and check in deep.
> Both of SSPTx and SSPRx are sometime update, not only one like i said before.
>
> For ts7400,I use virt_to_bus only for address that i got from "kmalloc", for 
> SSPDR -address for SSPTX and SSPRx-, I doesn't use it.
>
> On the morning,I tried to use it with SSPDR. There is nothing comtout from 
> SSP.
> I thoght address of SSPDR is physical addresses by default for EP9302 on 
> TS7400.
>
> I try to use bus_to_virt with the memory that use for keeping data from 
> SSPRx. It's the same result.
>
> Anyway,Thanks so much, I learn a lot from you.
>
> Now i looking for mor information about flush cache cpu which another one 
> tell me in another replying.
>
> I'm just read from a bit and it seem have a useful for me.
> I'll try and update to you again if any progress.
>
>
> --- In  Abid Rashid <> wrote:
>   
>> Â 
>> It is important to map virtual addresses to physical addresses whenever you 
>> work with DMA. (Please note that virt_to_bus might restrict your cross 
>> platform portability). 
>> I am not sure which Addresses are you using for Rx. 
>>
>> Make sure you have mapped your DMA virtual addresses to Rx bus addresses 
>> and vice versa.U might use bus_to_virt on DMA Rx addresses and use this 
>> address to look at the data.
>> If any thing else I cant help....
>> Â 
>> br,
>> Abid
>> --- On Mon, 3/15/10, pakorn_0608 <> wrote:
>>
>>
>> From: pakorn_0608 <>
>> Subject: [ts-7000] Re: DMA with SSP on TS7400
>> To: 
>> Date: Monday, March 15, 2010, 11:31 PM
>>
>>
>> Â  
>>
>>
>>
>> Thanks a lot, Abid :-)
>>
>> The virt_to_bus it's work for me.
>> bit by bit between SSPtx and SSP_CLK is come out correctly, but, i have new 
>> problem now.
>>
>> Only SSPTx right , SSPRx is sometime right.
>> I use printk" for show what i got from SSPRx by using DMA.
>> On start up module,after enable DMA, the memory of SSPRx that i allocate for 
>> DMA, It's sometime show my default value which i set it up on initial, but, 
>> sometime it show correct value follow by what it get from SSPRx.
>>
>> I'm finding the way to solve it.
>> Could you have any suggestion to me?
>>
>> Pakorn
>>
>> --- In  .com, Abid Rashid <abidrashid24@ ...> wrote:
>>     
>>>  
>>> Kmalloc returned addresses need to be mapped to the bus addresses.
>>> Use
>>> bus_addr = virt_to_bus( virt_addr/ *returned from kmalloc*/);
>>> address as the dma destination.
>>> Hope it would help
>>> br,
>>> Abid
>>>
>>> --- On Mon, 3/15/10, pakorn_0608 <pakorn_0608@ ...> wrote:
>>>
>>>
>>> From: pakorn_0608 <pakorn_0608@ ...>
>>> Subject: [ts-7000] DMA with SSP on TS7400
>>> To:  .com
>>> Date: Monday, March 15, 2010, 3:21 AM
>>>
>>>
>>>   
>>>
>>>
>>>
>>> Dear members,
>>>
>>> I'm use DMA on M2M mode with SSP, both of SSPTx and SSPRx for each channel.
>>>
>>> I have a bit problem with data that transmit and receive from SSP.
>>>
>>> I use "kmalloc" to get allocate memory address and i write some data into 
>>> that address.
>>> I can write and read correctly by using "printk".
>>>
>>> I'm also use it with SSPDR for transmit data from SPI by "outl" command, 
>>> data come out from SSPTx with clock sync correctly.
>>>
>>> Anyway,It's wrong when i'm using with DMA register.
>>>
>>> For example, DMA M2M0 using with SSPtx, I set DMA register, source register 
>>> with address from kmalloc "0xd120_10eo" , destination address SSPDR 
>>> "0x808A_0008" and BCR by 3.
>>>
>>> There are data come out from SSPtx but it is not right value that it should 
>>> be in memory address shown by "printk".
>>>
>>> Could someone have some suggest to me for using DMA with SSP for 7400 board?
>>>
>>> ************ *******
>>> example with some coding:
>>> ************ *******
>>>
>>> /* I write it for kernel module*/
>>> ...
>>> char *buffer_dma[ MAX_EP93XX_ DMA_M2M_CHANNELS ];
>>> .
>>> .
>>> .
>>> buffer_dma[0] = kmalloc( size , GFP_KERNEL|GFP_ DMA); /* example size is 
>>> 10*/
>>>
>>> for(i=0;i<10; i++)
>>> {
>>> buffer_dma[0] [i] = i*10;
>>>
>>> printk("Address of buffer_dma[0] [%d] = 0x%lx\n",i,( unsigned long)&buffer_ 
>>> dma[0][i] );
>>> printk("Value of buffer_dma[0] [%d] = %d\n",i,buffer_ dma[0][i] );
>>> }
>>>
>>> /*
>>> I print this value for show address and value
>>> my address for buffer_dma[0] [0] is "0xd120_10eo" and value is 0
>>> next, address for buffer_dma[0] [1] is "0xd120_10e1" and value is 10... and 
>>> other value is shown correctly.
>>>
>>> I also use with SSP
>>>
>>> */
>>>
>>> for(i=0;i<10; i++)
>>> {
>>> outl(buffer_ dma[0][i] , SSPDR );
>>> }
>>>
>>> /*
>>> I'm set SSP 8 bit,
>>> data come out from SSPTx is correctly , compare bit by bit with ssp_clock
>>>
>>> next i'm usongit with DMA M2M for SSPTx
>>>
>>> */
>>>
>>> outl(&buffer_ dma[0][0] , m2m_channel[ channel]. base + M2M_SAR_BASE0) ;
>>> outl( SSPDR , m2m_channel[ channel]. base + M2M_DAR_BASE0) ;
>>> outl(3 , m2m_channel[ channel]. base + M2M_BCR0);
>>>
>>> /*
>>> After that i'm enable DMA 
>>> my data that come out from SSPTx is wrong all,
>>> even i change data in my buffer_dma[0] [i] on above 
>>> data come out from SSPTx is still the same value.
>>> It's not match with it should be in memory address
>>> */
>>>
>>>       
>
>
>
>
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