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Date: Wed, 17 Apr 2024 20:22:04 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To: Frank Li <Frank.li@nxp.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>, Jingoo Han <jingoohan1@gmail.com>,
	Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kw@linux.com>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>, imx@lists.linux.dev,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	devicetree@vger.kernel.org
Subject: Re: [PATCH v6 5/5] PCI: dwc: Add generic MSG TLP support for sending
 PME_Turn_Off when system suspend
Message-ID: <20240417145204.GA15187@thinkpad>
References: <20240415-pme_msg-v6-0-56dad968ad3a@nxp.com>
 <20240415-pme_msg-v6-5-56dad968ad3a@nxp.com>
 <20240417101944.GG3894@thinkpad>
 <Zh/ezLdct9sisvhc@lizhi-Precision-Tower-5810>
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In-Reply-To: <Zh/ezLdct9sisvhc@lizhi-Precision-Tower-5810>

On Wed, Apr 17, 2024 at 10:38:04AM -0400, Frank Li wrote:
> On Wed, Apr 17, 2024 at 03:49:44PM +0530, Manivannan Sadhasivam wrote:
> > On Mon, Apr 15, 2024 at 03:33:29PM -0400, Frank Li wrote:
> > > 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.
> > > 
> > > The reserve space at end is a little bit better than alloc_resource()
> > > because the below reasons.
> > > - alloc_resource() will allocate space at begin of IORESOURCE_MEM window.
> > > There will be a hole when first Endpoint Device (EP) try to alloc a bigger
> > > space then 'region_align' size.
> > > - Keep EP device's IORESOURCE_MEM space unchange with/without this patch.
> > > 
> > 
> > I'd rewrite the above sentence as:
> > 
> > '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.'
> > 
> > > 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@nxp.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 3a9cb4be22ab2..5001cdf220123 100644
> > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > > @@ -398,6 +398,31 @@ 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 */
> > 
> > 		/*
> > 		 * Allocate MSG TLP region of size 'region_align' at the end of
> > 		 * the host bridge window.
> > 		 */
> > 
> > > +		res->start = win->res->end - pci->region_align + 1;
> > > +		res->end = win->res->end;
> > > +		res->name = "msg";
> > > +		res->flags = win->res->flags | IORESOURCE_BUSY;
> > > +
> > > +		if (!devm_request_resource(pci->dev, win->res, res))
> > > +			pp->msg_res = res;
> > > +		else
> > > +			devm_kfree(pci->dev, res);
> > 
> > You are explicitly freeing 'msg_res' everywhere. So either drop devm_ or rely
> > on devm to free the memory.
> > 
> > > +	}
> > > +}
> > > +
> > >  int dw_pcie_host_init(struct dw_pcie_rp *pp)
> > >  {
> > >  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> > > @@ -484,6 +509,16 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
> > >  
> > >  	dw_pcie_iatu_detect(pci);
> > >  
> > > +	/*
> > > +	 * Allocate the resource for MSG TLP before programming the iATU outbound window in
> > > +	 * dw_pcie_setup_rc(). Since the allocation depends on the value of 'region_align', this has
> > > +	 * to be done after dw_pcie_iatu_detect().
> > 
> > Please wrap the comments to 80 columns.
> 
> New code style is 100 columns. does comments still stick to 80 columns?
> 

That's only applicable for code and not comments. I also learned that some time
back.

- Mani

> > 
> > > +	 *
> > > +	 * Glue driver need set use_atu_msg before dw_pcie_host_init() if want MSG TLP feature.
> > 
> > How about,
> > 
> > 	 * Glue drivers need to set 'use_atu_msg' before dw_pcie_host_init() to
> > 	 * make use of the generic MSG TLP implementation.
> > 
> > > +	 */
> > > +	if (pp->use_atu_msg)
> > > +		dw_pcie_host_request_msg_tlp_res(pp);
> > > +
> > >  	ret = dw_pcie_edma_detect(pci);
> > >  	if (ret)
> > >  		goto err_free_msi;
> > > @@ -541,6 +576,11 @@ void dw_pcie_host_deinit(struct dw_pcie_rp *pp)
> > >  
> > >  	dw_pcie_edma_remove(pci);
> > >  
> > > +	if (pp->msg_res) {
> > > +		release_resource(pp->msg_res);
> > > +		devm_kfree(pci->dev, pp->msg_res);
> > > +	}
> > > +
> > >  	if (pp->has_msi_ctrl)
> > >  		dw_pcie_free_msi(pp);
> > >  
> > > @@ -702,6 +742,10 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
> > >  		atu.pci_addr = entry->res->start - entry->offset;
> > >  		atu.size = resource_size(entry->res);
> > >  
> > > +		/* MSG TLB window resource reserve at one of end of IORESOURCE_MEM resource */
> > 
> > How about,
> > 
> > 		/* Adjust iATU size if MSG TLP region was allocated before */
> > 		if (pp->msg_res && pp->msg_res->parent == entry->res)
> > 			atu.size = resource_size(entry->res) -
> > 					resource_size(pp->msg_res);
> > 		else
> > 			atu.size = resource_size(entry->res);
> > 
> > > +		if (pp->msg_res && pp->msg_res->parent == entry->res)
> > > +			atu.size -= resource_size(pp->msg_res);
> > > +
> > >  		ret = dw_pcie_prog_outbound_atu(pci, &atu);
> > >  		if (ret) {
> > >  			dev_err(pci->dev, "Failed to set MEM range %pr\n",
> > > @@ -733,6 +777,8 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
> > >  		dev_warn(pci->dev, "Ranges exceed outbound iATU size (%d)\n",
> > >  			 pci->num_ob_windows);
> > >  
> > > +	pp->msg_atu_index = i;
> > > +
> > >  	i = 0;
> > >  	resource_list_for_each_entry(entry, &pp->bridge->dma_ranges) {
> > >  		if (resource_type(entry->res) != IORESOURCE_MEM)
> > > @@ -838,11 +884,48 @@ int dw_pcie_setup_rc(struct dw_pcie_rp *pp)
> > >  }
> > >  EXPORT_SYMBOL_GPL(dw_pcie_setup_rc);
> > >  
> > > +/* Using message outbound ATU to send out PME_Turn_Off message for dwc PCIe controller */
> > 
> > No need of this comment.
> > 
> > > +static int dw_pcie_pme_turn_off(struct dw_pcie *pci)
> > > +{
> > > +	struct dw_pcie_ob_atu_cfg atu = { 0 };
> > > +	void __iomem *mem;
> > > +	int ret;
> > > +
> > > +	if (pci->num_ob_windows <= pci->pp.msg_atu_index)
> > > +		return -EINVAL;
> > 
> > 		return -ENOSPC;
> > 
> > > +
> > > +	if (!pci->pp.msg_res)
> > > +		return -EINVAL;
> > 
> > 		return -ENOSPC;
> > - Mani
> > 
> > -- 
> > மணிவண்ணன் சதாசிவம்

-- 
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