On Wed, Sep 21, 2022 at 09:27:35PM +0000, Will McVicker wrote: > From: Sajid Dalvi <sdalvi@xxxxxxxxxx> > > The PCIe r6.0, sec 5.9 spec requires a 10ms D3hot delay (defined by > PCI_PM_D3HOT_WAIT) for transitions to or from D3hot. So let's switch to > usleep_range() for 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 usleep_range() > therefore decreases the resume time on a Pixel 6 on average by 9ms. > > Note: some ancient Intel chips do have a quirk that sets the delay to > 120ms. Using usleep_delay() may add a few extra milliseconds for those > chips. > > [1] https://android.googlesource.com/kernel/gs/+/18a8cad68d8e6d50f339a716a18295e6d987cee3 > > Signed-off-by: Sajid Dalvi <sdalvi@xxxxxxxxxx> > Signed-off-by: Will McVicker <willmcvicker@xxxxxxxxxx> > Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx> Applied to pci/pm for v6.1, thanks, Will! > --- > drivers/pci/pci.c | 16 +++++++++------- > 1 file changed, 9 insertions(+), 7 deletions(-) > > v4: > * Drop use of msleep() in favor of always using usleep_range(). > * Update the commit message. > > v3: > * Use DIV_ROUND_CLOSEST instead of bit manipulation. > * Minor refactor to use max() where relavant. > > v2: > * Update to use 20-25% upper bound > * Update to use usleep_range() for <=20ms, else use msleep() > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 516bf0c2ca02..2127aba3550b 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -66,13 +66,15 @@ struct pci_pme_device { > > static void pci_dev_d3_sleep(struct pci_dev *dev) > { > - unsigned int delay = dev->d3hot_delay; > - > - if (delay < pci_pm_d3hot_delay) > - delay = pci_pm_d3hot_delay; > - > - if (delay) > - msleep(delay); > + unsigned int delay_ms = max(dev->d3hot_delay, pci_pm_d3hot_delay); > + unsigned int upper; > + > + if (delay_ms) { > + /* Use a 20% upper bound, 1ms minimum */ > + upper = max(DIV_ROUND_CLOSEST(delay_ms, 5), 1U); > + usleep_range(delay_ms * USEC_PER_MSEC, > + (delay_ms + upper) * USEC_PER_MSEC); > + } > } > > bool pci_reset_supported(struct pci_dev *dev) > > base-commit: fcf773ae8016c6bffe5d408d3eda50d981b946e6 > -- > 2.37.3.968.ga6b4b080e4-goog >
