RE: DMA transfer using McSPI driver

["Krishna Prasad Herur" <kherur@nextwave.com>]

Hi Senthil & Girish,
	I appreciate your answers. 

I am not sure if I understand you completely. I have been able to raw
reads and writes outside the IRQ handler.

Are you saying, I need to do a raw write followed by a dma transmit in
the IRQ context?

Here is another weird thing I see. After loading the McSPI driver
module, I configure, and enable the channel. I have not called the
mcspi_transmit_buf function. I already see the interrupt happening. Is
this normal? Below is the Debug log.
---------------------------------------------------------
MCSPI: exiting omap2_mcspi_register_isr ret: 0
MCSPI: entering omap2_mcspi_dma_writereq
MCSPI INFO: R[0xd8098000+0x2c]=0x12fc8
MCSPI INFO: W[0xd8098000+0x2c]=0x12fc8
MCSPI: entering omap2_mcspi_enable_channel
MCSPI INFO: R[0xd8098000+0x34]=0x0
MCSPI INFO: W[0xd8098000+0x34]=0x1
MCSPI INFO: R[0xd8098000+0x18]=0x1
MCSPI INFO: W[0xd8098000+0x34]=0x0
MCSPI INFO: W[0xd8098000+0x18]=0x3
McSpi Intr status = 3
MCSPI: exiting omap2_mcspi_enable_channel ret: 0
MCSPI: entering omap2_mcspi_transmit_buf
MCSPI INFO: R[0xd8098000+0x2c]=0x12fc8
MCSPI INFO: W[0xd8098000+0x2c]=0x16fc8
MCSPI: entering spi_dma_write_channel
MCSPI: exiting omap2_mcspi_transmit_buf ret: 0
--------------------------------------------------------

When I do not register dma_tx_callback function, and do a
mcspi_transmit_buf, I see 2words of garbage, followed by good data. Do
you know what could be causing this?

Thanks,
-Prasad


-----Original Message-----
From: Guruswamy, Senthilvadivu [mailto:svadivu@ti.com] 
Sent: Friday, February 02, 2007 12:20 AM
To: Krishna Prasad Herur
Cc: linux-omap-open-source@linux.omap.com; Ghongadematt, Girish
Subject: RE: DMA transfer using McSPI driver

Hi,

Mcspi transfer with raw mode can be done using the APIs
omap2_mcspi_raw_writetochannel(), omap2_mcspi_raw_readfromchannel().
Since it is a serial peripheral, you shall call these APIs in the tx/rx
IRQ handlers registered by you.

Regards,
Senthil.

-----Original Message-----
From: linux-omap-open-source-bounces@linux.omap.com
[mailto:linux-omap-open-source-bounces@linux.omap.com] On Behalf Of
Krishna Prasad Herur
Sent: Friday, February 02, 2007 7:50 AM
To: Ghongadematt, Girish
Cc: linux-omap-open-source@linux.omap.com
Subject: RE: DMA transfer using McSPI driver

If I understand the McSPI spec correctly, I should be able to enable a
channel, and then do a mcspi_transmit_buf. Also, the McSpi driver code
talks about the client/user maintaining the RAW/DMA mode. I do not see
any functions or variables that retain such info. (other than the
omap2_mcspi_set_dma_write macro)

In my case, I see the DMA data only when I configure the channel, do a
dma_transmit, and then enable the McSpi channel. This seems very weird,
and DMA transfers fail after switching from RAW mode to DMA mode. I have
tried many combinations of reserving, releasing the channels before
switching from RAW to DMA mode. 

Can someone shed light on the procedure to switch from raw mode to DMA
mode?

Here is how I got DMA to work.
<Call all config macros>
	omap2_mcspi_set_dma_write(mySpiDev, OMAP2_McSPI_CHAN_DMA_WRITE);
	omap2_mcspi_request_interface(devPtr);	
	omap2_mcspi_get(devPtr);
	omap2_mcspi_config_channel(devPtr);
	omap2_mcspi_dma_writereq(devPtr,OMAP2_McSPI_DMAW_ENABLE);
	omap2_mcspi_transmit_buf(devPtr,virt_to_phys((u32
*)dmaBuf),256);
	omap2_mcspi_enable_channel(devPtr);

Thanks,
-Prasad


-----Original Message-----
From: Girish. S. G. [mailto:girishsg@ti.com] 
Sent: Wednesday, January 31, 2007 5:34 AM
To: Krishna Prasad Herur
Cc: linux-omap-open-source@linux.omap.com
Subject: RE: DMA transfer using McSPI driver

hi prasad,

If you have called all config macros correctly (like, set and get
transmission
enable on line 1/0 etc,.) then there shoudn't b any problem.

Just check once if you are allocating memory for DMA buf properly.

regards,
girish

> I think I know the reason for the soft lockup.
>
> The omap 2430 errata says that the DMA Tx complete interrupt continues
> to be asserted after a transaction error. I found this to be the
reason
> for the soft lockup. I am still unsure as to why there is a
transaction
> error!
>
>
>
> The McSpi driver configuration for DMA transfer seems to be
> straightforward. The McSpi driver seems to be calling all the Dma
driver
> functions with the right parameters.
>
>
>
> Does anyone had success doing DMA transfers to/from McSpi channels
using
> the Omap McSpi driver?
>
> Regards,
>
> -Prasad
>
>
>
> ________________________________
>
> From: Krishna Prasad Herur
> Sent: Tuesday, January 23, 2007 12:02 PM
> To: linux-omap-open-source@linux.omap.com
> Subject: DMA transfer using McSPI driver
>
>
>
> Hi Gurus,
>
>             I was able to get raw data transfers over the McSPI bus on
> an Omap 2430 based platform running Linux 2.6. I am trying to do the
> same transmit using DMA. Is it possible to use DMA in polling mode? I
> have not registered interrupt handlers or dma handlers.  Below is the
> programming sequence I followed, after calling all the config macros.
>
>
>
>       omap2_mcspi_request_interface(devPtr);
>
>       omap2_mcspi_interface_reset(devPtr);
>
>       omap2_mcspi_get(devPtr);
>
>       omap2_mcspi_config_channel(devPtr);
>
>       omap2_mcspi_enable_channel(devPtr);
>
>       omap2_mcspi_dma_writereq(devPtr,OMAP2_McSPI_DMAW_ENABLE);
>
>       omap2_mcspi_transmit_buf(devPtr,dmaBuf,8);
>
>
>
> I get a DMA transaction error, and a soft lockup.
>
>
>
> DMA transaction error occurred with device 35
>
> BUG: soft lockup detected on CPU#0!
>
>
>
> Regards,
>
> -Prasad
>
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> Linux-omap-open-source@linux.omap.com
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>



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