[PATCH 0/4] PCI: dwc: Link Up IRQ fixes

[PATCH 0/4] PCI: dwc: Link Up IRQ fixes

[Niklas Cassel]

Hello there,

Commit 8d3bf19f1b58 ("PCI: dwc: Don't wait for link up if driver can detect
Link Up event") added support for DWC to not wait for link up before
enumerating the bus. However, we cannot simply enumerate the bus after
receiving a Link Up IRQ, we still need to wait PCIE_T_RRS_READY_MS time
to allow a device to become ready after deasserting PERST. To avoid
bringing back an conditional delay during probe, perform the wait in the
threaded IRQ handler instead.

Please review.


Kind regards,
Niklas


Niklas Cassel (4):
  PCI: dw-rockchip: Do not enumerate bus before endpoint devices are
    ready
  PCI: qcom: Do not enumerate bus before endpoint devices are ready
  PCI: dw-rockchip: Replace PERST sleep time with proper macro
  PCI: qcom: Replace PERST sleep time with proper macro

 drivers/pci/controller/dwc/pcie-dw-rockchip.c | 3 ++-
 drivers/pci/controller/dwc/pcie-qcom.c        | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

-- 
2.49.0

[PATCH 1/4] PCI: dw-rockchip: Do not enumerate bus before endpoint devices are ready

[Niklas Cassel]

Commit ec9fd499b9c6 ("PCI: dw-rockchip: Don't wait for link since we can
detect Link Up") changed so that we no longer call dw_pcie_wait_for_link(),
and instead enumerate the bus when receiving a Link Up IRQ.

Laszlo Fiat reported (off-list) that his PLEXTOR PX-256M8PeGN NVMe SSD is
no longer functional, and simply reverting commit ec9fd499b9c6 ("PCI:
dw-rockchip: Don't wait for link since we can detect Link Up") makes his
SSD functional again.

It seems that we are enumerating the bus before the endpoint is ready.
Adding a msleep(PCIE_T_RRS_READY_MS) before enumerating the bus in the
threaded IRQ handler makes the SSD functional once again.

What appears to happen is that before ec9fd499b9c6, we called
dw_pcie_wait_for_link(), and in the first iteration of the loop, the link
will never be up (because the link was just started),
dw_pcie_wait_for_link() will then sleep for LINK_WAIT_SLEEP_MS (90 ms),
before trying again.

This means that even if a driver was missing a msleep(PCIE_T_RRS_READY_MS)
(100 ms), because of the call to dw_pcie_wait_for_link(), enumerating the
bus would essentially be delayed by that time anyway (because of the sleep
LINK_WAIT_SLEEP_MS (90 ms)).

While we could add the msleep(PCIE_T_RRS_READY_MS) after deasserting PERST,
that would essentially bring back an unconditional delay during synchronous
probe (the whole reason to use a Link Up IRQ was to avoid an unconditional
delay during probe).

Thus, add the msleep(PCIE_T_RRS_READY_MS) before enumerating the bus in the
IRQ handler. This way, we will not have an unconditional delay during boot
for unpopulated PCIe slots.

Cc: Laszlo Fiat <laszlo.fiat@proton.me>
Fixes: ec9fd499b9c6 ("PCI: dw-rockchip: Don't wait for link since we can detect Link Up")
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
Hello Laszlo,

I know you have already tested this, but could you please send
your Tested-by tag to this patch?

 drivers/pci/controller/dwc/pcie-dw-rockchip.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
index 7a6a95dc877a..ed8e3dfe80e0 100644
--- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
+++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
@@ -471,6 +471,7 @@ static irqreturn_t rockchip_pcie_rc_sys_irq_thread(int irq, void *arg)
 	if (reg & PCIE_RDLH_LINK_UP_CHGED) {
 		if (rockchip_pcie_link_up(pci)) {
 			dev_dbg(dev, "Received Link up event. Starting enumeration!\n");
+			msleep(PCIE_T_RRS_READY_MS);
 			/* Rescan the bus to enumerate endpoint devices */
 			pci_lock_rescan_remove();
 			pci_rescan_bus(pp->bridge->bus);
-- 
2.49.0

Re: [PATCH 1/4] PCI: dw-rockchip: Do not enumerate bus before endpoint devices are ready

[Niklas Cassel]

On Mon, May 05, 2025 at 11:26:05AM +0200, Niklas Cassel wrote:
> diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> index 7a6a95dc877a..ed8e3dfe80e0 100644
> --- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> +++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> @@ -471,6 +471,7 @@ static irqreturn_t rockchip_pcie_rc_sys_irq_thread(int irq, void *arg)
>  	if (reg & PCIE_RDLH_LINK_UP_CHGED) {
>  		if (rockchip_pcie_link_up(pci)) {
>  			dev_dbg(dev, "Received Link up event. Starting enumeration!\n");
> +			msleep(PCIE_T_RRS_READY_MS);
>  			/* Rescan the bus to enumerate endpoint devices */
>  			pci_lock_rescan_remove();
>  			pci_rescan_bus(pp->bridge->bus);
> -- 
> 2.49.0
> 

Bah.. this patch is missing
+#include "../../pci.h"

missed during rebase.

(pcie-qcom.c already includes this.)

Will send a V2.


Kind regards,
Niklas

[PATCH 2/4] PCI: qcom: Do not enumerate bus before endpoint devices are ready

[Niklas Cassel]

Commit 36971d6c5a9a ("PCI: qcom: Don't wait for link if we can detect Link
Up") changed so that we no longer call dw_pcie_wait_for_link(), and instead
enumerate the bus when receiving a Link Up IRQ.

Before 36971d6c5a9a, we called dw_pcie_wait_for_link(), and in the first
iteration of the loop, the link will never be up (because the link was just
started), dw_pcie_wait_for_link() will then sleep for LINK_WAIT_SLEEP_MS
(90 ms), before trying again.

This means that even if a driver was missing a msleep(PCIE_T_RRS_READY_MS)
(100 ms), because of the call to dw_pcie_wait_for_link(), enumerating the
bus would essentially be delayed by that time anyway (because of the sleep
LINK_WAIT_SLEEP_MS (90 ms)).

While we could add the msleep(PCIE_T_RRS_READY_MS) after deasserting PERST
(qcom already has an unconditional 1 ms sleep after deasserting PERST),
that would essentially bring back an unconditional delay during probe (the
whole reason to use a Link Up IRQ was to avoid an unconditional delay
during probe).

Thus, add the msleep(PCIE_T_RRS_READY_MS) before enumerating the bus in the
IRQ handler. This way, for qcom SoCs that has a link up IRQ, we will not
have a 100 ms unconditional delay during boot for unpopulated PCIe slots.

Fixes: 36971d6c5a9a ("PCI: qcom: Don't wait for link if we can detect Link Up")
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 6b18a2775e7f..5cef5e92b173 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1646,6 +1646,7 @@ static irqreturn_t qcom_pcie_global_irq_thread(int irq, void *data)
 
 	if (FIELD_GET(PARF_INT_ALL_LINK_UP, status)) {
 		dev_dbg(dev, "Received Link up event. Starting enumeration!\n");
+		msleep(PCIE_T_RRS_READY_MS);
 		/* Rescan the bus to enumerate endpoint devices */
 		pci_lock_rescan_remove();
 		pci_rescan_bus(pp->bridge->bus);
-- 
2.49.0

[PATCH 3/4] PCI: dw-rockchip: Replace PERST sleep time with proper macro

[Niklas Cassel]

Replace the PERST sleep time with the proper macro (PCIE_T_PVPERL_MS).
No functional change.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/pci/controller/dwc/pcie-dw-rockchip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
index ed8e3dfe80e0..eb2931b39f7a 100644
--- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
+++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
@@ -231,7 +231,7 @@ static int rockchip_pcie_start_link(struct dw_pcie *pci)
 	 * We need more extra time as before, rather than setting just
 	 * 100us as we don't know how long should the device need to reset.
 	 */
-	msleep(100);
+	msleep(PCIE_T_PVPERL_MS);
 	gpiod_set_value_cansleep(rockchip->rst_gpio, 1);
 
 	return 0;
-- 
2.49.0

[PATCH 4/4] PCI: qcom: Replace PERST sleep time with proper macro

[Niklas Cassel]

Replace the PERST sleep time with the proper macro (PCIE_T_PVPERL_MS).
No functional change.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 5cef5e92b173..b1b89d5cb86a 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -301,7 +301,7 @@ static void qcom_ep_reset_assert(struct qcom_pcie *pcie)
 static void qcom_ep_reset_deassert(struct qcom_pcie *pcie)
 {
 	/* Ensure that PERST has been asserted for at least 100 ms */
-	msleep(100);
+	msleep(PCIE_T_PVPERL_MS);
 	gpiod_set_value_cansleep(pcie->reset, 0);
 	usleep_range(PERST_DELAY_US, PERST_DELAY_US + 500);
 }
-- 
2.49.0