Re: [PATCH v2 2/4] ata_piix: unify code for programming PIO and MWDMA timings

From: Bartlomiej Zolnierkiewicz
Date: Fri Oct 14 2011 - 09:50:47 EST


Sergei Shtylyov wrote:

> Hello.
>
> On 13-10-2011 17:39, Bartlomiej Zolnierkiewicz wrote:
>
> > From: Bartlomiej Zolnierkiewicz<bzolnier@xxxxxxxxx>
> > Subject: [PATCH v2] ata_piix: unify code for programming PIO and MWDMA timings
>
> > Besides making things noticably simpler it results in ~2% decrease in
> > the driver LOC count and also ~2% decrease in the driver binary size
> > (as measured on x86-32).
>
> > Fix piix_set_piomode() documentation while at it.
>
> > Signed-off-by: Bartlomiej Zolnierkiewicz<bzolnier@xxxxxxxxx>
>
> I'm still inclined to NAK this patch.
>
> > ---
> > v2: remove use_mwdma variable and fix comment style
>
> > earlier references:
> > https://lkml.org/lkml/2011/2/8/99
> >
> > drivers/ata/ata_piix.c | 111 ++++++++++++++++---------------------------------
> > 1 file changed, 38 insertions(+), 73 deletions(-)
>
> > Index: b/drivers/ata/ata_piix.c
> > ===================================================================
> > --- a/drivers/ata/ata_piix.c
> > +++ b/drivers/ata/ata_piix.c
> [...]
> > @@ -811,31 +822,20 @@ static void do_pata_set_dmamode(struct a
> [...]
> > - if (ap->udma_mask)
> > - pci_read_config_byte(dev, 0x48,&udma_enable);
>
> Don't think you should remove this.
>
> > -
> > if (speed>= XFER_UDMA_0) {
> > - unsigned int udma = adev->dma_mode - XFER_UDMA_0;
> > + unsigned int udma = speed - XFER_UDMA_0;
> > u16 udma_timing;
> > u16 ideconf;
> > int u_clock, u_speed;
> >
> > + spin_lock_irqsave(&piix_lock, flags);
> > +
> > + pci_read_config_byte(dev, 0x48, &udma_enable);
>
> But you should also clear the UDMA enable bit when setting an MWDMA mode, no?
>
> > +
> > /*
> > * UDMA is handled by a combination of clock switching and
> > * selection of dividers
> > @@ -868,56 +868,21 @@ static void do_pata_set_dmamode(struct a
> > performance (WR_PingPong_En) */
> > pci_write_config_word(dev, 0x54, ideconf);
> > }
> > +
> > + pci_write_config_byte(dev, 0x48, udma_enable);
> > +
> > + spin_unlock_irqrestore(&piix_lock, flags);
> > } else {
> > - /*
> > - * MWDMA is driven by the PIO timings. We must also enable
> > - * IORDY unconditionally along with TIME1. PPE has already
> > - * been set when the PIO timing was set.
> > - */
> > - unsigned int mwdma = adev->dma_mode - XFER_MW_DMA_0;
> > - unsigned int control;
> > - u8 slave_data;
> > + /* MWDMA is driven by the PIO timings. */
> > + unsigned int mwdma = speed - XFER_MW_DMA_0;
> > const unsigned int needed_pio[3] = {
> > XFER_PIO_0, XFER_PIO_3, XFER_PIO_4
> > };
> > int pio = needed_pio[mwdma] - XFER_PIO_0;
> >
> [...]
> > - if (ap->udma_mask)
> > - udma_enable&= ~(1<< devid);
>
> Still don't understand why you're removing this code.
>
> > -
> > - pci_write_config_word(dev, master_port, master_data);
> > + /* XFER_PIO_0 is never used currently */
> > + piix_set_timings(ap, adev, pio);
> > }
> > - /* Don't scribble on 0x48 if the controller does not support UDMA */
> > - if (ap->udma_mask)
> > - pci_write_config_byte(dev, 0x48, udma_enable);
>
> Should have kept this one too...

We still have following code at the end of piix_set_timings():

/* Ensure the UDMA bit is off - it will be turned back on if
UDMA is selected */

if (ap->udma_mask) {
pci_read_config_byte(dev, 0x48, &udma_enable);
udma_enable &= ~(1 << (2 * ap->port_no + adev->devno));
pci_write_config_byte(dev, 0x48, udma_enable);
}

so everything should be OK.

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