PCI: dwc: Add generic MSG TLP support for sending PME_Turn_Off when system suspend

Instead of relying on the vendor specific implementations to send the
PME_Turn_Off message, introduce a generic way of sending the message using
the MSG TLP.

This is achieved by reserving a region for MSG TLP of size
'pci->region_align', at the end of the first IORESOURCE_MEM window of the
host bridge. And then sending the PME_Turn_Off message during system
suspend with the help of iATU.

The reason for reserving the MSG TLP region at the end of the
IORESOURCE_MEM is to avoid generating holes in between, because when the
region is allocated using allocate_resource(), memory will be allocated
from the start of the window. Later, if memory gets allocated for an
endpoint of size bigger than 'region_align', there will be a hole between
MSG TLP region and endpoint memory.

This generic implementation is optional for the glue drivers and can be
overridden by a custom 'pme_turn_off' callback.

Link: https://lore.kernel.org/linux-pci/20240418-pme_msg-v8-5-a54265c39742@nxp.com
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 4a3973935979..39ec253df6cf 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -340,6 +340,9 @@ struct dw_pcie_rp {
 	struct pci_host_bridge  *bridge;
 	raw_spinlock_t		lock;
 	DECLARE_BITMAP(msi_irq_in_use, MAX_MSI_IRQS);
+	bool			use_atu_msg;
+	int			msg_atu_index;
+	struct resource		*msg_res;
 };
 
 struct dw_pcie_ep_ops {