Re: [PATCH 2/3] drivers/ide/pci/sc1200.c: remove pointless hwif lookup loop

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Friday 26 October 2007, Jeff Garzik wrote:
> Bartlomiej Zolnierkiewicz wrote:
> > On Thursday 25 October 2007, Jeff Garzik wrote:
> >> Store our hwif indices at probe time, in order to eliminate a needless
> >> and ugly loop across all hwifs, searching for our pci device.
> > 
> > It seems that we can simplify it even further and remove knowledge about
> > hwifs altogether from suspend/resume methods.
> > 
> >> Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
> >> ---
> >>  drivers/ide/pci/sc1200.c |   76 +++++++++++++++++++++++++++++++---------------
> >>  1 files changed, 51 insertions(+), 25 deletions(-)
> >>
> >> diff --git a/drivers/ide/pci/sc1200.c b/drivers/ide/pci/sc1200.c
> >> index d2c8b55..17e58d6 100644
> >> --- a/drivers/ide/pci/sc1200.c
> >> +++ b/drivers/ide/pci/sc1200.c
> >> @@ -41,6 +41,8 @@
> >>  #define PCI_CLK_66	0x02
> >>  #define PCI_CLK_33A	0x03
> >>  
> >> +#define SC1200_IFS	4
> >> +
> >>  static unsigned short sc1200_get_pci_clock (void)
> >>  {
> >>  	unsigned char chip_id, silicon_revision;
> >> @@ -261,31 +263,32 @@ static void sc1200_set_pio_mode(ide_drive_t *drive, const u8 pio)
> >>  }
> >>  
> >>  #ifdef CONFIG_PM
> >> -static ide_hwif_t *lookup_pci_dev (ide_hwif_t *prev, struct pci_dev *dev)
> >> -{
> >> -	int	h;
> >> -
> >> -	for (h = 0; h < MAX_HWIFS; h++) {
> >> -		ide_hwif_t *hwif = &ide_hwifs[h];
> >> -		if (prev) {
> >> -			if (hwif == prev)
> >> -				prev = NULL;	// found previous, now look for next match
> >> -		} else {
> >> -			if (hwif && hwif->pci_dev == dev)
> >> -				return hwif;	// found next match
> >> -		}
> >> -	}
> >> -	return NULL;	// not found
> >> -}
> >> -
> >>  typedef struct sc1200_saved_state_s {
> >>  	__u32		regs[4];
> >>  } sc1200_saved_state_t;
> >>  
> >> +static unsigned int pack_hwif_idx(u8 *idx)
> >> +{
> >> +	return	(((unsigned int) idx[0]) << 0) |
> >> +		(((unsigned int) idx[1]) << 8) |
> >> +		(((unsigned int) idx[2]) << 16) |
> >> +		(((unsigned int) idx[3]) << 24);
> >> +}
> >> +
> >> +static ide_hwif_t *sc1200_hwif(struct pci_dev *pdev, unsigned int iface)
> >> +{
> >> +	unsigned int packed_hwifs, idx;
> >> +
> >> +	packed_hwifs = (unsigned long) pci_get_drvdata(pdev);
> >> +	idx = (packed_hwifs >> (iface * 8)) & 0xff;
> >> +
> >> +	return (idx == 0xff) ? NULL : &ide_hwifs[idx];
> >> +}
> >>  
> >>  static int sc1200_suspend (struct pci_dev *dev, pm_message_t state)
> >>  {
> >> -	ide_hwif_t		*hwif = NULL;
> >> +	ide_hwif_t		*hwif;
> >> +	int			i;
> >>  
> >>  	printk("SC1200: suspend(%u)\n", state.event);
> >>  
> >> @@ -295,9 +298,14 @@ static int sc1200_suspend (struct pci_dev *dev, pm_message_t state)
> >>  		//
> >>  		// Loop over all interfaces that are part of this PCI device:
> >>  		//
> >> -		while ((hwif = lookup_pci_dev(hwif, dev)) != NULL) {
> >> +		for (i = 0; i < SC1200_IFS; i++) {
> >>  			sc1200_saved_state_t	*ss;
> >>  			unsigned int		basereg, r;
> >> +
> >> +			hwif = sc1200_hwif(dev, i);
> >> +			if (!hwif)
> >> +				continue;
> >> +
> >>  			//
> >>  			// allocate a permanent save area, if not already allocated
> >>  			//
> >> @@ -310,7 +318,7 @@ static int sc1200_suspend (struct pci_dev *dev, pm_message_t state)
> >>  			}
> >>  			ss = (sc1200_saved_state_t *)hwif->config_data;
> >>  			//
> >> -			// Save timing registers:  this may be unnecessary if 
> >> +			// Save timing registers:  this may be unnecessary if
> >>  			// BIOS also does it
> >>  			//
> >>  			basereg = hwif->channel ? 0x50 : 0x40;
> > 
> > Please take a close look at the line above and the next three lines:
> > 
> > for (r = 0; r < 4; ++r) {
> > 	pci_read_config_dword (hwif->pci_dev, basereg + (r<<2), &ss->regs[r]);
> > }
> > 
> > It is highly obfuscated but the sc1200_suspend() reads 16 bytes from
> > the offset 0x40 (for the primary port) and puts them in the corresponding
> > struct sc1200_saved_state_s buffer, then it reads another 16 bytes from the
> > offset 0x50 (for the secondary port) and puts it in the another buffer.
> > 
> > In summary sc1200_suspend() reads 32 continuous bytes from offset 0x40
> > and the exactly reverse operation happens in sc1200_resume().
> > 
> > Given that and the fact that struct sc1200_save_state_s buffers are used
> > _only_ by sc1200_{suspend,resume}() we may safely convert the code to use
> > one buffer for both ports (the whole PCI device).  We just need to bump
> > the size of struct sc1200_saved_state_s (from 4 to 8 double-words) and use
> > pci_{get,set}_drvdata() instead of hwif->config_data.  Then we can remove
> > looping over interfaces completely from sc1200_{suspend,resume}()! :)
> 
> May I assume you'll handle that task?  :)  It sounds like you have a far 
> better idea than mine, and my main goal -- fixing bugs and warning -- is 
> accomplished anyway with the merging of patch #3.

Uh, OK...

[PATCH] sc1200: remove pointless hwif lookup loop

Save PCI regs values for both IDE ports in one buffer, in order to eliminate
a needless and ugly loop across all hwifs, searching for our PCI device.

Partially based on the previous patch by Jeff Garzik.

Cc: Jeff Garzik <jeff@garzik.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
---
 drivers/ide/pci/sc1200.c |  106 ++++++++++++++++-------------------------------
 1 file changed, 37 insertions(+), 69 deletions(-)

Index: b/drivers/ide/pci/sc1200.c
===================================================================
--- a/drivers/ide/pci/sc1200.c
+++ b/drivers/ide/pci/sc1200.c
@@ -261,66 +261,39 @@ static void sc1200_set_pio_mode(ide_driv
 }
 
 #ifdef CONFIG_PM
-static ide_hwif_t *lookup_pci_dev (ide_hwif_t *prev, struct pci_dev *dev)
-{
-	int	h;
-
-	for (h = 0; h < MAX_HWIFS; h++) {
-		ide_hwif_t *hwif = &ide_hwifs[h];
-		if (prev) {
-			if (hwif == prev)
-				prev = NULL;	// found previous, now look for next match
-		} else {
-			if (hwif && hwif->pci_dev == dev)
-				return hwif;	// found next match
-		}
-	}
-	return NULL;	// not found
-}
-
-typedef struct sc1200_saved_state_s {
-	__u32		regs[4];
-} sc1200_saved_state_t;
-
+struct sc1200_saved_state {
+	u32 regs[8];
+};
 
 static int sc1200_suspend (struct pci_dev *dev, pm_message_t state)
 {
-	ide_hwif_t		*hwif = NULL;
-
 	printk("SC1200: suspend(%u)\n", state.event);
 
+	/*
+	 * we only save state when going from full power to less
+	 */
 	if (state.event == PM_EVENT_ON) {
-		// we only save state when going from full power to less
+		struct sc1200_saved_state *ss;
+		unsigned int r;
 
-		//
-		// Loop over all interfaces that are part of this PCI device:
-		//
-		while ((hwif = lookup_pci_dev(hwif, dev)) != NULL) {
-			sc1200_saved_state_t	*ss;
-			unsigned int		basereg, r;
-			//
-			// allocate a permanent save area, if not already allocated
-			//
-			ss = (sc1200_saved_state_t *)hwif->config_data;
-			if (ss == NULL) {
-				ss = kmalloc(sizeof(sc1200_saved_state_t), GFP_KERNEL);
-				if (ss == NULL)
-					return -ENOMEM;
-				hwif->config_data = (unsigned long)ss;
-			}
-			ss = (sc1200_saved_state_t *)hwif->config_data;
-			//
-			// Save timing registers:  this may be unnecessary if 
-			// BIOS also does it
-			//
-			basereg = hwif->channel ? 0x50 : 0x40;
-			for (r = 0; r < 4; ++r) {
-				pci_read_config_dword (hwif->pci_dev, basereg + (r<<2), &ss->regs[r]);
-			}
+		/*
+		 * allocate a permanent save area, if not already allocated
+		 */
+		ss = (struct sc1200_saved_state *)pci_get_drvdata(dev);
+		if (ss == NULL) {
+			ss = kmalloc(sizeof(*ss), GFP_KERNEL);
+			if (ss == NULL)
+				return -ENOMEM;
+			pci_set_drvdata(dev, ss);
 		}
-	}
 
-	/* You don't need to iterate over disks -- sysfs should have done that for you already */ 
+		/*
+		 * save timing registers
+		 * (this may be unnecessary if BIOS also does it)
+		 */
+		for (r = 0; r < 8; r++)
+			pci_read_config_dword(dev, 0x40 + r * 4, &ss->regs[r]);
+	}
 
 	pci_disable_device(dev);
 	pci_set_power_state(dev, pci_choose_state(dev, state));
@@ -329,30 +302,25 @@ static int sc1200_suspend (struct pci_de
 
 static int sc1200_resume (struct pci_dev *dev)
 {
-	ide_hwif_t	*hwif = NULL;
-	int		i;
+	struct sc1200_saved_state *ss;
+	unsigned int r;
+	int i;
 
 	i = pci_enable_device(dev);
 	if (i)
 		return i;
 
-	//
-	// loop over all interfaces that are part of this pci device:
-	//
-	while ((hwif = lookup_pci_dev(hwif, dev)) != NULL) {
-		unsigned int		basereg, r;
-		sc1200_saved_state_t	*ss = (sc1200_saved_state_t *)hwif->config_data;
-
-		//
-		// Restore timing registers:  this may be unnecessary if BIOS also does it
-		//
-		basereg = hwif->channel ? 0x50 : 0x40;
-		if (ss != NULL) {
-			for (r = 0; r < 4; ++r) {
-				pci_write_config_dword(hwif->pci_dev, basereg + (r<<2), ss->regs[r]);
-			}
-		}
+	ss = (struct sc1200_saved_state *)pci_get_drvdata(dev);
+
+	/*
+	 * restore timing registers
+	 * (this may be unnecessary if BIOS also does it)
+	 */
+	if (ss) {
+		for (r = 0; r < 8; r++)
+			pci_write_config_dword(dev, 0x40 + r * 4, ss->regs[r]);
 	}
+
 	return 0;
 }
 #endif