[PATCH v4 3/7] PCI: intel-gw: Move interrupt enable to own function

[Florian Eckert <fe@dev.tdt.de>]

To improve the readability of the code, move the interrupt enable
instructions to a separate function. That is already done for the disable
interrupt instruction.

In addition, all pending interrupts are cleared and disabled, just as this
is done in the disable function 'intel_pcie_core_irq_disable()'. After
that, all relevant interrupts are enabled again. The 'PCIE_APP_IRNEN'
definition contains all the relevant interrupts that are of interest.

This change is also done in the MaxLinear SDK [1]. As I unfortunately
don’t have any documentation for this IP core, I suspect that the
intention is to set the IP core for interrupt handling to a specific
state. Perhaps the problem is that the IP core did not reinitialize the
interrupt register properly after a power cycle.

In my view, it can’t do any harm to switch the interrupt off and then on
again to set them to a specific state.

The reason why the MaxLinear SDK is used as a reference here is, that this
pcie dwc IP is used in the URX851 and URX850 SoC. This SoC was originally
developed by Intel when they acquired Lantiq’s home networking division in
2015 [2]. In 2020 the home network division was sold to MaxLinear [3].
Since then, this SoC belongs to MaxLinear. They use their own SDK,
which runs on kernel version '5.15.x'.

[1] https://github.com/maxlinear/linux/blob/updk_9.1.90/drivers/pci/controller/dwc/pcie-intel-gw.c#L431
[2] https://www.intc.com/news-events/press-releases/detail/364/intel-to-acquire-lantiq-advancing-the-connected-home
[3] https://investors.maxlinear.com/press-releases/detail/395/maxlinear-to-acquire-intels-home-gateway-platform

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
---
 drivers/pci/controller/dwc/pcie-intel-gw.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-intel-gw.c b/drivers/pci/controller/dwc/pcie-intel-gw.c
index 80d1607c46cbbb1e274b37a0bb9377a877678f5d..e88b8243cc41c607c39e4d58c4dcd8c8c082e8b0 100644
--- a/drivers/pci/controller/dwc/pcie-intel-gw.c
+++ b/drivers/pci/controller/dwc/pcie-intel-gw.c
@@ -195,6 +195,13 @@ static void intel_pcie_device_rst_deassert(struct intel_pcie *pcie)
 	gpiod_set_value_cansleep(pcie->reset_gpio, 0);
 }
 
+static void intel_pcie_core_irq_enable(struct intel_pcie *pcie)
+{
+	pcie_app_wr(pcie, PCIE_APP_IRNEN, 0);
+	pcie_app_wr(pcie, PCIE_APP_IRNCR, PCIE_APP_IRN_INT);
+	pcie_app_wr(pcie, PCIE_APP_IRNEN, PCIE_APP_IRN_INT);
+}
+
 static void intel_pcie_core_irq_disable(struct intel_pcie *pcie)
 {
 	pcie_app_wr(pcie, PCIE_APP_IRNEN, 0);
@@ -316,9 +323,7 @@ static int intel_pcie_host_setup(struct intel_pcie *pcie)
 	if (ret)
 		goto app_init_err;
 
-	/* Enable integrated interrupts */
-	pcie_app_wr_mask(pcie, PCIE_APP_IRNEN, PCIE_APP_IRN_INT,
-			 PCIE_APP_IRN_INT);
+	intel_pcie_core_irq_enable(pcie);
 
 	return 0;
 

-- 
2.47.3