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Message-ID: <47214223.40909@garzik.org> Date: Thu, 25 Oct 2007 21:25:55 -0400 From: Jeff Garzik <jeff@...zik.org> To: Bartlomiej Zolnierkiewicz <bzolnier@...il.com> 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 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. Jeff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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