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> --- 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
