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    SubjectRe: [PATCH 02/20] ata_piix: unify code for programming PIO and MWDMA timings
    On 08.02.2011 15:23, Bartlomiej Zolnierkiewicz wrote:

    > From ca6c1fbc7d853829524b87a3bcbbb1f67796281c Mon Sep 17 00:00:00 2001
    > From: Bartlomiej Zolnierkiewicz<bzolnier@gmail.com>
    > Date: Tue, 8 Feb 2011 12:39:24 +0100
    > Subject: [PATCH 02/20] 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@gmail.com>
    [...]

    > diff --git a/drivers/ata/ata_piix.c b/drivers/ata/ata_piix.c
    > index 0f4856d..c954f91 100644
    > --- a/drivers/ata/ata_piix.c
    > +++ b/drivers/ata/ata_piix.c
    > @@ -696,22 +696,11 @@ static int piix_pata_prereset(struct ata_link *link, unsigned long deadline)
    >
    > static DEFINE_SPINLOCK(piix_lock);
    >
    > -/**
    > - * piix_set_piomode - Initialize host controller PATA PIO timings
    > - * @ap: Port whose timings we are configuring
    > - * @adev: um
    > - *
    > - * Set PIO mode for device, in host controller PCI config space.
    > - *
    > - * LOCKING:
    > - * None (inherited from caller).
    > - */
    > -
    > -static void piix_set_piomode(struct ata_port *ap, struct ata_device *adev)
    > +static void piix_set_timings(struct ata_port *ap, struct ata_device *adev,
    > + u8 pio, bool use_mwdma)
    > {
    > struct pci_dev *dev = to_pci_dev(ap->host->dev);
    > unsigned long flags;
    > - unsigned int pio = adev->pio_mode - XFER_PIO_0;
    > unsigned int is_slave = (adev->devno != 0);
    > unsigned int master_port= ap->port_no ? 0x42 : 0x40;
    > unsigned int slave_port = 0x44;
    > @@ -732,14 +721,18 @@ static void piix_set_piomode(struct ata_port *ap, struct ata_device *adev)
    > { 2, 1 },
    > { 2, 3 }, };
    >
    > - if (pio >= 2)
    > + if (pio >= 2 || use_mwdma)

    The 'use_mwdma' check is actually superfluous...

    > control |= 1; /* TIME1 enable */
    > - if (ata_pio_need_iordy(adev))
    > + if (ata_pio_need_iordy(adev) || use_mwdma)
    > control |= 2; /* IE enable */

    Why IORDY is enabled for MWDMA has always been beyond me... I understand
    that the stupid Intel docs are to be blamed here.

    > -
    > /* Intel specifies that the PPE functionality is for disk only */
    > if (adev->class == ATA_DEV_ATA)
    > control |= 4; /* PPE enable */
    > + /* If the drive MWDMA is faster than it can do PIO then
    > + we must force PIO into PIO0 */

    It's not the preferred multi-line comment style:

    /*
    * bla
    * bla
    */

    > + if (use_mwdma && adev->pio_mode < (XFER_PIO_0 + pio))

    Parens not needed around +.

    > @@ -803,31 +812,20 @@ static void do_pata_set_dmamode(struct ata_port *ap, struct ata_device *adev, in
    > {
    > struct pci_dev *dev = to_pci_dev(ap->host->dev);
    > unsigned long flags;
    > - u8 master_port = ap->port_no ? 0x42 : 0x40;
    > - u16 master_data;
    > u8 speed = adev->dma_mode;
    > int devid = adev->devno + 2 * ap->port_no;
    > u8 udma_enable = 0;
    >
    > - static const /* ISP RTC */
    > - u8 timings[][2] = { { 0, 0 },
    > - { 0, 0 },
    > - { 1, 0 },
    > - { 2, 1 },
    > - { 2, 3 }, };
    > -
    > - spin_lock_irqsave(&piix_lock, flags);
    > -
    > - pci_read_config_word(dev, master_port, &master_data);
    > - if (ap->udma_mask)
    > - pci_read_config_byte(dev, 0x48, &udma_enable);

    I don't think you should have removed that...

    > @@ -860,56 +858,20 @@ static void do_pata_set_dmamode(struct ata_port *ap, struct ata_device *adev, in
    > 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 {
    [...]
    > - if (ap->udma_mask)
    > - udma_enable &= ~(1 << devid);

    This does not seem correct -- you must disable UDMA when programming MWDMA.

    > -
    > - pci_write_config_word(dev, master_port, master_data);
    > + piix_set_timings(ap, adev, pio, 1);
    > }
    > - /* Don't scribble on 0x48 if the controller does not support UDMA */
    > - if (ap->udma_mask)
    > - pci_write_config_byte(dev, 0x48, udma_enable);
    > -
    > - spin_unlock_irqrestore(&piix_lock, flags);
    > }
    >
    > /**

    WBR, Sergei


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