DMA Generic Task

[Pedro Luis D. L.]

Hello,
I´m developing an small module to use the DMA API to copy some audio data in a PSC wich has attached an digital to analog converter. It is only a proof of concept before I can use this information to develop an audio driver for the SPI interface. 
I´m using a 2.6.20 kernel patched with the bestcomm patches from http://www.246tnt.com/mpc52xx/dev_full/ at Sylvain's page. 
My board is also a pcm030. I had the same problems with the Ethernet so I decided to keep the old fec driver with the old bestcomm driver also just for the Ethernet stuff until I could take a look over it.
I took a look into the code for the bestcomm API for the generic tasks and thought that this was the way to initialize the bestcomm task:

        struct bcom_task *tx_bcom;   
        struct bcom_task *rx_bcom;
	
        switch(psc_num) {
		case 1:
			initiator_tx = SDMA_INITIATOR_PSC1_TX;
			initiator_rx = SDMA_INITIATOR_PSC1_RX;
			break;
		case 2:
			initiator_tx = SDMA_INITIATOR_PSC2_TX;
			initiator_rx = SDMA_INITIATOR_PSC2_RX;
			break;
		default:
			panic("snd-SPImgt.o: invalid value for psc_num (%i)\n",psc_num);
			break;
	};

	tx_bcom = bcom_gen_bd_tx_init(512, MPC52xx_PA(MPC52xx_PSCx_OFFSET(psc_num))+0x80, initiator_tx, 6);   //(1)

	rx_bcom = bcom_gen_bd_rx_init(512, MPC52xx_PA(MPC52xx_PSCx_OFFSET(psc_num))+0x60, initiator_rx, 6, 1024);


where MPC52xx_PA(MPC52xx_PSCx_OFFSET(psc_num)) = 0xf0002000, wich added to 0x80 or 0x60 gives TXFIFO or RXFIFO's physical address.
However, when I insert the module, it crashes at (1) Line (bcom_gen_bd_tx_init...) with this output:

root at MPC5200B:~ insmod SPIspeaker
Inserting SPIspeaker module
Unable to handle kernel paging request for data at address 0x0000000c
Faulting instruction address: 0xc001525c
Oops: Kernel access of bad area, sig: 11 [#1]
PREEMPT
Modules linked in: SPIspeaker eeprom
NIP: C001525C LR: C0016458 CTR: 00000010
REGS: c3e7bd80 TRAP: 0300   Not tainted  (2.6.20)
MSR: 00009032   CR: 24008222  XER: 00000000
DAR: 0000000C, DSISR: 20000000
TASK = c3f2c7b0[447] 'insmod' THREAD: c3e7a000
GPR00: 00000010 C3E7BE30 C3F2C7B0 00000200 00000008 00000010 00000006 00004000
GPR08: C3E7A000 00000000 00000000 C0016430 24008222 1008B4E8 00000000 00000000
GPR16: 00000012 00000011 C5068C74 C3FD08C0 00000000 00000056 C024408C 00000000
GPR24: C01E28DC 00000008 C0260000 00000200 0000000E 00000010 00000006 C0244338
Call Trace:
[C3E7BE30] [C5060000]  (unreliable)
[C3E7BE60] [C0016458]
[C3E7BE80] [C506026C]
[C3E7BEA0] [C003F804]
[C3E7BF40] [C000F5C8]
--- Exception: c01Instruction dump:
7c7b1b78 90010034 7c992378 7cbd2b78 8128000c 39290001 9128000c 3f40c026
38000010 813a01a8 7c0903a6 39400000  7d695b78 396b0004 800b0000
 note: insmod[447] exited with preempt_count 1
BUG: scheduling while atomic: insmod/0x10000001/447
Call Trace:
[C3E7BB80] [C00081E0]  (unreliable)
[C3E7BBB0] [C01DDCB0]
[C3E7BC00] [C0017CD8]
[C3E7BC10] [C01DE924]
[C3E7BC20] [C00520C0]
[C3E7BCA0] [C0055B0C]
[C3E7BCD0] [C001A764]
[C3E7BCE0] [C001E8A0]
[C3E7BD00] [C0020428]
[C3E7BD40] [C000DB84]
[C3E7BD60] [C0011084]
[C3E7BD70] [C000FA64]
--- Exception: 300[C3E7BE30] [C5060000]  (unreliable)
[C3E7BE60] [C0016458]
[C3E7BE80] [C506026C]
[C3E7BEA0] [C003F804]
[C3E7BF40] [C000F5C8]
--- Exception: c01Segmentation fault

How should I use the API to initialize the Bestcomm task?


Regards,
Pedro Dominguez

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