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Message-Id: <200710312253.31434.bzolnier@gmail.com>
Date: Wed, 31 Oct 2007 22:53:31 +0100
From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To: Jeff Garzik <jeff@...zik.org>
Cc: LKML <linux-kernel@...r.kernel.org>, linux-ide@...r.kernel.org,
akpm@...ux-foundation.org
Subject: Re: [PATCH 2/3] drivers/ide/pci/sc1200.c: remove pointless hwif lookup loop
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@...hat.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@...zik.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.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
-
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