linux-kernel - Re: [PATCH v5 5/5] PCI: dwc: Add common send PME_Turn

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Message-ID: <20240406040131.GC2678@thinkpad>
Date: Sat, 6 Apr 2024 09:31:31 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Frank Li <Frank.li@....com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, Jingoo Han <jingoohan1@...il.com>,
	Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, imx@...ts.linux.dev,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v5 5/5] PCI: dwc: Add common send PME_Turn_Off message
 method

On Fri, Apr 05, 2024 at 10:31:16AM -0400, Frank Li wrote:
> On Fri, Apr 05, 2024 at 11:54:26AM +0530, Manivannan Sadhasivam wrote:
> > On Tue, Mar 19, 2024 at 12:07:15PM -0400, Frank Li wrote:
> > 
> > PCI: dwc: Add generic MSG TLP support for sending PME_Turn_Off during system suspend
> > 
> > > Reserve space at end of first IORESOURCE_MEM window as message TLP MMIO
> > > window. This space's size is 'region_align'.
> > > 
> > > Set outbound ATU map memory write to send PCI message. So one MMIO write
> > > can trigger a PCI message, such as PME_Turn_Off.
> > > 
> > > Add common dwc_pme_turn_off() function.
> > > 
> > > Call dwc_pme_turn_off() to send out PME_Turn_Off message in general
> > > dw_pcie_suspend_noirq() if there are not platform callback pme_turn_off()
> > > exist.
> > > 
> > 
> > How about:
> > 
> > "Instead of relying on the vendor specific implementations to send the
> > PME_Turn_Off message, let's 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.
> > 
> > It should be noted that this generic implementation is optional for the glue
> > drivers and can be overridden by a custom 'pme_turn_off' callback."
> > 
> > > Signed-off-by: Frank Li <Frank.Li@....com>
> > > ---
> > >  drivers/pci/controller/dwc/pcie-designware-host.c | 94 ++++++++++++++++++++++-
> > >  drivers/pci/controller/dwc/pcie-designware.h      |  3 +
> > >  2 files changed, 93 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> > > index 267687ab33cbc..d5723fce7a894 100644
> > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > > @@ -393,6 +393,31 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
> > >  	return 0;
> > >  }
> > >  
> > > +static void dw_pcie_host_request_msg_tlp_res(struct dw_pcie_rp *pp)
> > > +{
> > > +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> > > +	struct resource_entry *win;
> > > +	struct resource *res;
> > > +
> > > +	win = resource_list_first_type(&pp->bridge->windows, IORESOURCE_MEM);
> > > +	if (win) {
> > > +		res = devm_kzalloc(pci->dev, sizeof(*res), GFP_KERNEL);
> > > +		if (!res)
> > > +			return;
> > > +
> > > +		/* Reserve last region_align block as message TLP space */
> > > +		res->start = win->res->end - pci->region_align + 1;
> > > +		res->end = win->res->end;
> > 
> > Don't you need to adjust the host bridge window size and end address?
> 
> Needn't. request_resource will reserve it from bridge window. Like malloc,
> if you malloc to get a region of memory, which will never get by malloc
> again utill you call free.
> 

Hmm, will that modify the window->res->end address and size?

> > 
> > > +		res->name = "msg";
> > > +		res->flags = win->res->flags | IORESOURCE_BUSY;
> > > +
> > 
> > Shouldn't this resource be added back to the host bridge?
> 
> No, this resource will reserver for msg only for whole bridge life cycle.
> Genenally alloc resource only happen at PCI devices probe. All pci space
> will be fixed after system probe.
> 

I don't think so. This resource still belongs to the host bridge, so we should
add it back.

- Mani

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