[PATCH v2] mfd: intel-lpss: Set d3hot_delay to 0

[PATCH v2] mfd: intel-lpss: Set d3hot_delay to 0

[Navon John Lukose]

intel-lpss-pci already clears d3cold_delay, but every runtime resume of an
LPSS controller still sleeps the default 10 ms d3hot_delay in
pci_power_up().

The PCI spec asks for those 10 ms on D3hot->D0. Mika pointed out that the
LPSS controllers are not really PCI-connected devices, so the delay is
likely not needed. quirk_remove_d3hot_delay() drops it on several older
Intel chipsets, Cherry Trail among them, and commit 815b4448198f ("i3c:
mipi-i3c-hci-pci: Set d3hot_delay to 0 for Intel controllers") does the
same for the Intel I3C controllers.

Nothing misbehaves with the delay in place, so this only shortens resume.
On Arrow Lake-H (Lenovo Yoga Pro 7 14IAH10) the touchpad's I2C controller
autosuspends after 1 s idle, and the first report afterwards waits for the
resume. With d3hot_delay set to 0 the i2c-hid interrupt handler for that
report takes 1.1-1.9 ms instead of 12.6-14.4 ms, with no I2C errors. Only
Arrow Lake-H was tested.

Signed-off-by: Navon John Lukose <navonjohnlukose@gmail.com>
---

Notes:
    Changes since RFC:
    - Drop RFC and add the review discussion to the changelog (Andy).
    
    RFC: https://lore.kernel.org/r/20261016114347.23633-1-navonjohnlukose@gmail.com

 drivers/mfd/intel-lpss-pci.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mfd/intel-lpss-pci.c b/drivers/mfd/intel-lpss-pci.c
index 63a3fb58566..5672f033e5c 100644
--- a/drivers/mfd/intel-lpss-pci.c
+++ b/drivers/mfd/intel-lpss-pci.c
@@ -70,6 +70,7 @@ static int intel_lpss_pci_probe(struct pci_dev *pdev,
 		info->quirks = quirk_pci_info->driver_data;
 
 	pdev->d3cold_delay = 0;
+	pdev->d3hot_delay = 0;
 
 	/* Probably it is enough to set this for iDMA capable devices only */
 	pci_set_master(pdev);
-- 
2.56.0

Re: [PATCH v2] mfd: intel-lpss: Set d3hot_delay to 0

[Mika Westerberg]

On Thu, Oct 22, 2026 at 09:34:53AM +0530, Navon John Lukose wrote:
> intel-lpss-pci already clears d3cold_delay, but every runtime resume of an
> LPSS controller still sleeps the default 10 ms d3hot_delay in
> pci_power_up().
> 
> The PCI spec asks for those 10 ms on D3hot->D0. Mika pointed out that the
> LPSS controllers are not really PCI-connected devices, so the delay is
> likely not needed. quirk_remove_d3hot_delay() drops it on several older
> Intel chipsets, Cherry Trail among them, and commit 815b4448198f ("i3c:
> mipi-i3c-hci-pci: Set d3hot_delay to 0 for Intel controllers") does the
> same for the Intel I3C controllers.
> 
> Nothing misbehaves with the delay in place, so this only shortens resume.
> On Arrow Lake-H (Lenovo Yoga Pro 7 14IAH10) the touchpad's I2C controller
> autosuspends after 1 s idle, and the first report afterwards waits for the
> resume. With d3hot_delay set to 0 the i2c-hid interrupt handler for that
> report takes 1.1-1.9 ms instead of 12.6-14.4 ms, with no I2C errors. Only
> Arrow Lake-H was tested.
> 
> Signed-off-by: Navon John Lukose <navonjohnlukose@gmail.com>

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>