linux-kernel - Re: [PATCH 13/15] ide: fix UDMA/MWDMA/SWDMA masks

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Date:	Tue, 23 Jan 2007 17:51:03 +0300
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	Alan <alan@...rguk.ukuu.org.uk>
Cc:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/15] ide: fix UDMA/MWDMA/SWDMA masks

Hello.

Alan wrote:
>>>>   Ugh, I'm not seeing any *actual* support for MW/SW DMA in this driver... 

>>>Thats long been broken. Should be correct in the libata driver

>>    Here's a surprise for you. pata_cmd64x copied the SW/MW DMA setup code 
>>from the IDE driver.  No way it could be working.  You may check against the 
>>PC64x datasheets (if you have them -- if you don't I think I may share) and 
>>see for yourself -- it's abolutely idiotic.

    I.e. MWDMA2 should be working due to the way the driver is written (it 
sets up PIO4 timings when auto-tuning DMA) but not the other modes since 
speedproc() method is brain-damaged in this part.

> 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...

> 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...

MBR, Sergei
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