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Date: Wed, 17 Apr 2024 15:49:44 +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: <20240417101944.GG3894@thinkpad>
References: <20240415-pme_msg-v6-0-56dad968ad3a@nxp.com>
 <20240415-pme_msg-v6-5-56dad968ad3a@nxp.com>
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In-Reply-To: <20240415-pme_msg-v6-5-56dad968ad3a@nxp.com>

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.

> +	 *
> +	 * 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

-- 
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