linux-kernel - [PATCH v3 1/2] PCI: mediatek: Enable the whole memory mapped IO range

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Message-ID: <1548999367-11733-2-git-send-email-honghui.zhang@mediatek.com>
Date:   Fri, 1 Feb 2019 13:36:06 +0800
From:   <honghui.zhang@...iatek.com>
To:     <lorenzo.pieralisi@....com>, <bhelgaas@...gle.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <ryder.lee@...iatek.com>
CC:     <rafael.j.wysocki@...el.com>, <fred@...dlawl.com>,
        <poza@...eaurora.org>, <youlin.pei@...iatek.com>,
        <jianjun.wang@...iatek.com>,
        Honghui Zhang <honghui.zhang@...iatek.com>
Subject: [PATCH v3 1/2] PCI: mediatek: Enable the whole memory mapped IO range

From: Honghui Zhang <honghui.zhang@...iatek.com>

Mediatek's HW assigned a bus address range(typically start from
0x2000_0000 to 0x2fff_ffff for both mt2712 and mt7622) for PCIe usage.
This bus address range is called memory mapped IO range, when CPU or
other HW access those address, PCIe RC HW should response to this
access. Normally the RC will translate those access request to TLPs
and send to corresponding EP side. It's like the total memory address
resource which could be allocated by EP and RC's BARs.

Although those address range is available for allocated, but it should
be enabled by the PCIE_AHB_TRANS_BASE register, what size will be
enabled is determined by AHB2PCIE_SIZE bits in this register.

In previous code we did not enable the full size of HW assigned address
range, if the EP's BAR requested size is bigger than the size we enabled
and smaller than the HW available size. The access request which target
at these un-enabled address will be blocked by RC, and EP side will
never get those TLPs.

Previous code never run into a system error in production because even
half of those range(128MB) is bigger enough for typical EP device's BAR
request(4MB).

But all those HW assigned bus range should be enabled. And it's Okay to
do that. RC will never forward a request to EP when this request is not
suitable for EP's BAR range.

Using resource_size(mem) instead of mem->end - mem->start to fix this,
since the MMIO window size for both MT2712 and MT7622 are all
0x1000_0000, this change will change the values of fls(size) from
fls(0xfff_ffff) to fls(0x1000_0000) and calcalate the whole memory
mapped IO range size.

This change also eliminate the following complain generated by
scripts/coccinelle/api/resource_size.cocci:

pcie-mediatek.c:720:13-16: WARNING: Suspicious code. resource_size is maybe missing with mem

Signed-off-by: Honghui Zhang <honghui.zhang@...iatek.com>
---
 drivers/pci/controller/pcie-mediatek.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
index 55e471c..c42fe5c 100644
--- a/drivers/pci/controller/pcie-mediatek.c
+++ b/drivers/pci/controller/pcie-mediatek.c
@@ -654,7 +654,6 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 	struct resource *mem = &pcie->mem;
 	const struct mtk_pcie_soc *soc = port->pcie->soc;
 	u32 val;
-	size_t size;
 	int err;

 	/* MT7622 platforms need to enable LTSSM and ASPM from PCIe subsys */
@@ -706,8 +705,8 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 		mtk_pcie_enable_msi(port);

 	/* Set AHB to PCIe translation windows */
-	size = mem->end - mem->start;
-	val = lower_32_bits(mem->start) | AHB2PCIE_SIZE(fls(size));
+	val = lower_32_bits(mem->start) |
+	      AHB2PCIE_SIZE(fls(resource_size(mem)));
 	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);

 	val = upper_32_bits(mem->start);
-- 
2.6.4