From: Sajid Dalvi Date: Wed, 21 Sep 2022 21:27:35 +0000 (+0000) Subject: PCI/PM: Reduce D3hot delay with usleep_range() X-Git-Tag: v6.6.17~6385^2~13^2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=3e347969a5776947a115649dae740a9ed47473f5;p=platform%2Fkernel%2Flinux-rpi.git PCI/PM: Reduce D3hot delay with usleep_range() PCIe r6.0, sec 5.9, requires a 10ms delay between programming a device to change to or from D3hot and the time the device is next accessed (unless Readiness Notifications are used). The 10ms value (PCI_PM_D3HOT_WAIT) doesn't appear directly here because some chipsets require 120ms for devices *below* them (pci_pm_d3hot_delay) and some devices require more or less than 10ms (dev->d3hot_delay). But msleep(10) typically waits about *20*ms, which is more than we need. Switch to usleep_range() to improve the delay accuracy. Based on a commit from Sajid in the Pixel 6 kernel tree [1]. On a Pixel 6, the 10ms delay for the Exynos PCIe device delayed for an average of 19ms. Switching to usleep_range() decreased the resume time by about 9ms. [1] https://android.googlesource.com/kernel/gs/+/18a8cad68d8e6d50f339a716a18295e6d987cee3 [bhelgaas commit log, add timers-howto.rst link] Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/timers/timers-howto.rst?id=v5.19#n73 Link: https://lore.kernel.org/r/20220921212735.2131588-1-willmcvicker@google.com Signed-off-by: Sajid Dalvi Signed-off-by: Will McVicker Signed-off-by: Bjorn Helgaas Reviewed-by: Matthias Kaehlcke --- diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 107afa0..92c6f7e 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)