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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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