linux-kernel - [PATCH v2 08/13] PCI: dwc: Discard IP-core version checking on unrolled iATU detection

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Date:   Wed, 4 May 2022 00:22:55 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>
CC:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Frank Li <Frank.Li@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 08/13] PCI: dwc: Discard IP-core version checking on unrolled iATU detection

It's pretty much pointless. Even though unrolled version of the internal
ATU has been indeed available since DWC PCIe v4.80a IP-core, there is no
guarantee it was enabled during the IP-core configuration (Synopsys
suggests to contact the Solvnet support for guidance of how to do that for
the newer IP-cores). So the only reliable way to find out the unrolled
iATU feature availability is indeed to check the iATU viewport register
content. In accordance with the reference manual [1] if the register
doesn't exist (unrolled iATU is enabled) it's content is fixed with
0xff-s, otherwise it will contain some zeros. So we can freely drop the
IP-core version checking in this matter then and use the
dw_pcie_iatu_unroll_enabled() method only to detect whether iATU/eDMA
space is unrolled.

[1] DesignWare Cores, PCI Express Controller, Register Desciptions,
v.4.90a, December 2016, p.855

Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/pci/controller/dwc/pcie-designware.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 3bd1cfd12148..e3d2c11e6998 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -600,15 +600,15 @@ static void dw_pcie_link_set_max_speed(struct dw_pcie *pci, u32 link_gen)
 
 }
 
-static u8 dw_pcie_iatu_unroll_enabled(struct dw_pcie *pci)
+static bool dw_pcie_iatu_unroll_enabled(struct dw_pcie *pci)
 {
 	u32 val;
 
 	val = dw_pcie_readl_dbi(pci, PCIE_ATU_VIEWPORT);
 	if (val == 0xffffffff)
-		return 1;
+		return true;
 
-	return 0;
+	return false;
 }
 
 static void dw_pcie_iatu_detect_regions_unroll(struct dw_pcie *pci)
@@ -680,9 +680,8 @@ void dw_pcie_iatu_detect(struct dw_pcie *pci)
 	struct device *dev = pci->dev;
 	struct platform_device *pdev = to_platform_device(dev);
 
-	if (pci->version >= 0x480A || (!pci->version &&
-				       dw_pcie_iatu_unroll_enabled(pci))) {
-		pci->iatu_unroll_enabled = true;
+	pci->iatu_unroll_enabled = dw_pcie_iatu_unroll_enabled(pci);
+	if (pci->iatu_unroll_enabled) {
 		if (!pci->atu_base) {
 			struct resource *res =
 				platform_get_resource_byname(pdev, IORESOURCE_MEM, "atu");
-- 
2.35.1