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

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

[Bartlomiej Zolnierkiewicz]

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>
---
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
@@ -704,22 +704,11 @@ static int piix_pata_prereset(struct ata
 
 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)
 {
 	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;
@@ -744,10 +733,16 @@ static void piix_set_piomode(struct ata_
 		control |= 1;	/* TIME1 enable */
 	if (ata_pio_need_iordy(adev))
 		control |= 2;	/* IE enable */
-
 	/* 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
+	 */
+	if (adev->pio_mode < XFER_PIO_0 + pio)
+		/* Enable DMA timing only */
+		control |= 8;	/* PIO cycles in PIO0 */
 
 	spin_lock_irqsave(&piix_lock, flags);
 
@@ -796,6 +791,22 @@ static void piix_set_piomode(struct ata_
 }
 
 /**
+ *	piix_set_piomode - Initialize host controller PATA PIO timings
+ *	@ap: Port whose timings we are configuring
+ *	@adev: Drive in question
+ *
+ *	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)
+{
+	piix_set_timings(ap, adev, adev->pio_mode - XFER_PIO_0);
+}
+
+/**
  *	do_pata_set_dmamode - Initialize host controller PATA PIO timings
  *	@ap: Port whose timings we are configuring
  *	@adev: Drive in question
@@ -811,31 +822,20 @@ static void do_pata_set_dmamode(struct a
 {
 	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);
-
 	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);
+
 		/*
 		 * 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;
 
-		control = 3;	/* IORDY|TIME1 */
-
-		/* If the drive MWDMA is faster than it can do PIO then
-		   we must force PIO into PIO0 */
-
-		if (adev->pio_mode < needed_pio[mwdma])
-			/* Enable DMA timing only */
-			control |= 8;	/* PIO cycles in PIO0 */
-
-		if (adev->devno) {	/* Slave */
-			master_data &= 0xFF4F;  /* Mask out IORDY|TIME1|DMAONLY */
-			master_data |= control << 4;
-			pci_read_config_byte(dev, 0x44, &slave_data);
-			slave_data &= (ap->port_no ? 0x0f : 0xf0);
-			/* Load the matching timing */
-			slave_data |= ((timings[pio][0] << 2) | timings[pio][1]) << (ap->port_no ? 4 : 0);
-			pci_write_config_byte(dev, 0x44, slave_data);
-		} else { 	/* Master */
-			master_data &= 0xCCF4;	/* Mask out IORDY|TIME1|DMAONLY
-						   and master timing bits */
-			master_data |= control;
-			master_data |=
-				(timings[pio][0] << 12) |
-				(timings[pio][1] << 8);
-		}
-
-		if (ap->udma_mask)
-			udma_enable &= ~(1 << devid);
-
-		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);
-
-	spin_unlock_irqrestore(&piix_lock, flags);
 }
 
 /**

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

[Sergei Shtylyov]

Hello.

On 13-10-2011 17:39, 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...

MBR, Sergei

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

[Bartlomiej Zolnierkiewicz]

Sergei Shtylyov wrote:

> Hello.
> 
> On 13-10-2011 17:39, 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.

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

[Sergei Shtylyov]

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

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

[Sergei Shtylyov]

Hello.

On 10/14/2011 08:43 PM, Sergei Shtylyov 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
[...]

>> 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. :-)

    But I would have preferred the above code to be removed, of course.

WBR, Sergei