[lkml]   [2007]   [Jan]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 13/15] ide: fix UDMA/MWDMA/SWDMA masks

Sergei Shtylyov wrote:

>> Not a suprise to be honest. I fixed some of the ALi stuff when I did it
>> and I think that was pushed back into drivers/ide. The CMD64x hasn't had
>> much love really.

> Another buglet found by random glancing at this driver:

> /**
> * cmd648_dma_stop - DMA stop callback
> * @qc: Command in progress
> *
> * DMA has completed.
> */

> static void cmd648_bmdma_stop(struct ata_queued_cmd *qc)
> {
> struct ata_port *ap = qc->ap;
> struct pci_dev *pdev = to_pci_dev(ap->host->dev);
> u8 dma_intr;
> int dma_reg = ap->port_no ? ARTTIM23_INTR_CH1 : CFR_INTR_CH0;
> int dma_mask = ap->port_no ? ARTTIM2 : CFR;
> ata_bmdma_stop(qc);
> pci_read_config_byte(pdev, dma_reg, &dma_intr);
> pci_write_config_byte(pdev, dma_reg, dma_intr | dma_mask);
> }

> dma_reg and dma_mask initializers must have been swapped since
> ARTTIM2 and CFR are regster names. So, the code reads/writes
> semi-random regs...

BTW, on PCI0646U2 and later chips, the interrupt status (it's not really
DMA interrupt status but a latched INTRQ signal not "coupled" with DMA logic,
according to the datasheets) can be read from MRDMODE reg. which is accessible
in I/O space at BMIDE base + 1 which is certainly faster. That's what
drivers/ide/cmd64x.c is doing in its test_dma_irq() method (however, it's
doign this on PCI0643 and early revs of PCI0646 which don't have these bits).
The driver's dma_end() method is acting really strange: it checks if the cjip
is PCI-648/9 and reads the PCI config space to clear those interrupt bits
while these chips have them in I/O mapped MRDMODE; OTOH, it ignores these bits
on earlier chips which have them in oonfig. space only (CFR/ARTTIM23 regs)...
go figure. I'm going to clean this up but don't heve the h/w handy... :-/

>> Wouldn't mind the older 64x (not 640) data sheets if they are sharable.

> Sent what I had on this machine. Will looks for newer revision of
> PCJ0646U2 spec elsewhere...

Sent rev. 1.3... Hopefully will be updated.

MBR, Sergei
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2007-01-25 16:43    [from the cache]
©2003-2014 Jasper Spaans. hosted at Digital Ocean