[PATCH v2 3/9] PCI: dw-rockchip: Describe RK3588 BAR4 DMA ctrl window

[Niklas Cassel <cassel@kernel.org>]

From: Koichiro Den <den@valinux.co.jp>

On RK3588 PCIe3_4L in EP mode, the integrated DMA controller registers
are permanently mapped to BAR4 and must not be repurposed by EPF
drivers.

When the remote peer needs to access these registers, it must use the
fixed BAR4 window instead of creating another inbound mapping in a
different BAR. Mixing the fixed window with an additional mapping can
lead to incorrect behavior.

Advertise the DMA controller MMIO window as a reserved BAR subregion so
EPF drivers can reuse it safely.

Reviewed-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/pci/controller/dwc/pcie-dw-rockchip.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
index 5b17da63151d..ecc28093c589 100644
--- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
+++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
@@ -403,6 +403,15 @@ static const struct pci_epc_features rockchip_pcie_epc_features_rk3568 = {
 	.bar[BAR_5] = { .type = BAR_RESIZABLE, },
 };
 
+static const struct pci_epc_bar_rsvd_region rk3588_bar4_rsvd[] = {
+	{
+		/* DMA_CAP (BAR4: DMA Port Logic Structure) */
+		.type = PCI_EPC_BAR_RSVD_DMA_CTRL_MMIO,
+		.offset = 0x0,
+		.size = 0x2000,
+	},
+};
+
 /*
  * BAR4 on rk3588 exposes the ATU Port Logic Structure to the host regardless of
  * iATU settings for BAR4. This means that BAR4 cannot be used by an EPF driver,
@@ -420,7 +429,11 @@ static const struct pci_epc_features rockchip_pcie_epc_features_rk3588 = {
 	.bar[BAR_1] = { .type = BAR_RESIZABLE, },
 	.bar[BAR_2] = { .type = BAR_RESIZABLE, },
 	.bar[BAR_3] = { .type = BAR_RESIZABLE, },
-	.bar[BAR_4] = { .type = BAR_RESERVED, },
+	.bar[BAR_4] = {
+		.type = BAR_RESERVED,
+		.nr_rsvd_regions = ARRAY_SIZE(rk3588_bar4_rsvd),
+		.rsvd_regions = rk3588_bar4_rsvd,
+	},
 	.bar[BAR_5] = { .type = BAR_RESIZABLE, },
 };
 
-- 
2.53.0