Hi Will, On Wed, Aug 17, 2022 at 06:52:02PM +0000, Will McVicker wrote: > From: Sajid Dalvi <sdalvi@xxxxxxxxxx> > > Since the PCI spec requires a 10ms D3Hot delay (defined by > PCI_PM_D3HOT_WAIT) and a few of the PCI quirks update the D3Hot delay up > to 120ms, let's add support for both usleep_range and msleep based on > the delay time to improve the delay accuracy. > > This patch is based off of a commit from Sajid Dalvi <sdalvi@xxxxxxxxxx> > in the Pixel 6 kernel tree [1]. Testing on a Pixel 6, found that the > 10ms delay for the Exynos PCIe device was on average delaying for 19ms > when the spec requires 10ms. Switching from msleep to uslseep_range > therefore decreases the resume time on a Pixel 6 on average by 9ms. > > [1] https://android.googlesource.com/kernel/gs/+/18a8cad68d8e6d50f339a716a18295e6d987cee3 > > Signed-off-by: Sajid Dalvi <sdalvi@xxxxxxxxxx> > Signed-off-by: Will McVicker <willmcvicker@xxxxxxxxxx> > --- > drivers/pci/pci.c | 20 +++++++++++++++----- > 1 file changed, 15 insertions(+), 5 deletions(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 95bc329e74c0..97a042ca9032 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -63,16 +63,26 @@ struct pci_pme_device { > }; > > #define PME_TIMEOUT 1000 /* How long between PME checks */ > +#define MAX(a, b) ((a) >= (b) ? (a) : (b)) no need to define this macro, you can use max() from include/linux/minmax.h instead. > > static void pci_dev_d3_sleep(struct pci_dev *dev) > { > - unsigned int delay = dev->d3hot_delay; > + unsigned int delay_ms = dev->d3hot_delay; > > - if (delay < pci_pm_d3hot_delay) > - delay = pci_pm_d3hot_delay; > + if (delay_ms < pci_pm_d3hot_delay) > + delay_ms = pci_pm_d3hot_delay; nit: since you are already touching this code you could change it to: unsigned int delay_ms = max(dev->d3hot_delay, pci_pm_d3hot_delay); > > - if (delay) > - msleep(delay); > + if (delay_ms) { > + if (delay_ms <= 20) { > + /* Use a 20-25% upper bound with 1ms minimum */ > + unsigned int upper = MAX((delay_ms >> 3) << 1, 1); Not sure this optimization of using bit shifts instead of the clearer do_div() is really needed here. pci_dev_d3_sleep() is not a super hot code path IIUC. > + > + usleep_range(delay_ms * USEC_PER_MSEC, > + (delay_ms + upper) * USEC_PER_MSEC); > + } else { > + msleep(delay_ms); > + } > + } > } > > bool pci_reset_supported(struct pci_dev *dev) > > base-commit: 274a2eebf80c60246f9edd6ef8e9a095ad121264 > -- > 2.37.1.595.g718a3a8f04-goog >
