Re: [PATCH v2 08/27] pci: implement an emulated PCI-to-PCI bridge

From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	Jason Cooper <jason@lakedaemon.net>, Andrew Lunn <andrew@lunn.ch>,
	Gregory Clement <gregory.clement@free-electrons.com>,
	Arnd Bergmann <arnd@arndb.de>, Maen Suleiman <maen@marvell.com>,
	Lior Amsalem <alior@marvell.com>,
	Thierry Reding <thierry.reding@avionic-design.de>,
	Eran Ben-Avi <benavi@marvell.com>,
	Nadav Haklai <nadavh@marvell.com>,
	Shadi Ammouri <shadi@marvell.com>,
	Tawfik Bayouk <tawfik@marvell.com>,
	Stephen Warren <swarren@wwwdotorg.org>,
	Russell King - ARM Linux <linux@arm.linux.org.uk>
Subject: Re: [PATCH v2 08/27] pci: implement an emulated PCI-to-PCI bridge
Date: Mon, 28 Jan 2013 12:35:16 -0700	[thread overview]
Message-ID: <20130128193516.GB17722@obsidianresearch.com> (raw)
In-Reply-To: <1359399397-29729-9-git-send-email-thomas.petazzoni@free-electrons.com>

On Mon, Jan 28, 2013 at 07:56:17PM +0100, Thomas Petazzoni wrote:

> +int pci_sw_pci_bridge_read(struct pci_sw_pci_bridge *bridge,
> +			   unsigned int where, int size, u32 *value)
> +{
> +	switch (where & ~3) {

It is not essential, but desirable, to report an Express Root Port
capability for PCI-E bridges:

        Capabilities: [40] Express (v2) Root Port (Slot+), MSI 00
                DevCap: MaxPayload 128 bytes, PhantFunc 0, Latency L0s <64ns, L1 <1us
                        ExtTag- RBE+ FLReset-
                DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
                        RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
                        MaxPayload 128 bytes, MaxReadReq 128 bytes
                DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr+ TransPend-
                LnkCap: Port #1, Speed 5GT/s, Width x4, ASPM L0s L1, Latency L0 <1us, L1 <4us
                        ClockPM- Surprise- LLActRep+ BwNot-
                LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- Retrain- CommClk-
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
                LnkSta: Speed 2.5GT/s, Width x0, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt-
                SltCap: AttnBtn- PwrCtrl- MRL- AttnInd- PwrInd- HotPlug- Surprise-
                        Slot #0, PowerLimit 25.000W; Interlock- NoCompl+
                SltCtl: Enable: AttnBtn- PwrFlt- MRL- PresDet- CmdCplt- HPIrq- LinkChg-
                        Control: AttnInd Unknown, PwrInd Unknown, Power- Interlock-
                SltSta: Status: AttnBtn- PowerFlt- MRL- CmdCplt- PresDet- Interlock-
                        Changed: MRL- PresDet- LinkState-
                RootCtl: ErrCorrectable- ErrNon-Fatal- ErrFatal- PMEIntEna+ CRSVisible-
                RootCap: CRSVisible-
                RootSta: PME ReqID 0000, PMEStatus- PMEPending-
                DevCap2: Completion Timeout: Range BC, TimeoutDis+ ARIFwd-
                DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis- ARIFwd-
                LnkCtl2: Target Link Speed: 2.5GT/s, EnterCompliance- SpeedDis-, Selectable De-emphasis: -6dB
                         Transmit Margin: Normal Operating Range, EnterModifiedCompliance- ComplianceSOS-
                         Compliance De-emphasis: -6dB
                LnkSta2: Current De-emphasis Level: -3.5dB

In the Marvell case, this capability can be constructed by pulling
data from the the Express End Point capability of the PCI-E port:

        Capabilities: [60] Express (v2) Endpoint, MSI 00
                DevCap: MaxPayload 256 bytes, PhantFunc 0, Latency L0s <64ns, L1 unlimited
                        ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset-
                DevCtl: Report errors: Correctable- Non-Fatal+ Fatal+ Unsupported-
                        RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
                        MaxPayload 128 bytes, MaxReadReq 512 bytes
                DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend-
                LnkCap: Port #8, Speed 2.5GT/s, Width x8, ASPM L0s, Latency L0 unlimited, L1 unlimited
                        ClockPM- Surprise- LLActRep- BwNot-
                LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- Retrain- CommClk-
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
                LnkSta: Speed 2.5GT/s, Width x8, TrErr- Train- SlotClk- DLActive- BWMgmt- ABWMgmt-
                DevCap2: Completion Timeout: Range ABCD, TimeoutDis+
                DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-
                LnkCtl2: Target Link Speed: 2.5GT/s, EnterCompliance- SpeedDis-, Selectable De-emphasis: -6dB
                         Transmit Margin: Normal Operating Range, EnterModifiedCompliance- ComplianceSOS-
                         Compliance De-emphasis: -6dB
                LnkSta2: Current De-emphasis Level: -6dB

This lets user space see the width/speed/etc state of the PCI-E link
itself...

Jason