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

On 10/14/2011 05:43 PM, Bartlomiej Zolnierkiewicz wrote:

>>> From: Bartlomiej Zolnierkiewicz<bzolnier@gmail.com>
>>> 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@gmail.com>

>> 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.

Ah, I should have looked... Didn't expect it to be there, and it in fact
shouldn't be there, but now I'm OK with your patch. :-)

WBR, Sergei


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