Re: [PATCH v7 5/5] PCI: dwc: Add generic MSG TLP support for sending PME_Turn_Off when system suspend

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 Wilczyński" <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 v7 5/5] PCI: dwc: Add generic MSG TLP support for sending PME_Turn_Off when system suspend
Date: Thu, 18 Apr 2024 12:00:58 +0530	[thread overview]
Message-ID: <20240418063058.GE2861@thinkpad> (raw)
In-Reply-To: <20240417-pme_msg-v7-5-9c6208cda90f@nxp.com>

On Wed, Apr 17, 2024 at 12:59:43PM -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 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 | 102 ++++++++++++++++++++--
>  drivers/pci/controller/dwc/pcie-designware.h      |   3 +
>  2 files changed, 100 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 3a9cb4be22ab2..f57805b21ef53 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -398,6 +398,34 @@ 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;
> +
> +		/*
> +		 * 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 (!request_resource(win->res, res))
> +			pp->msg_res = res;
> +		else
> +			devm_kfree(pci->dev, res);

You still haven't resolved my earlier comment:

"You are explicitly freeing 'msg_res' everywhere. So either drop devm_ or rely
on devm to free the memory."

- Mani

> +	}
> +}
> +
>  int dw_pcie_host_init(struct dw_pcie_rp *pp)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> @@ -484,6 +512,18 @@ 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().
> +	 *
> +	 * 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 +581,11 @@ 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);
>  
> @@ -700,7 +745,13 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
>  		atu.type = PCIE_ATU_TYPE_MEM;
>  		atu.cpu_addr = entry->res->start;
>  		atu.pci_addr = entry->res->start - entry->offset;
> -		atu.size = resource_size(entry->res);
> +
> +		/* 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);
>  
>  		ret = dw_pcie_prog_outbound_atu(pci, &atu);
>  		if (ret) {
> @@ -733,6 +784,8 @@ 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 +891,47 @@ int dw_pcie_setup_rc(struct dw_pcie_rp *pp)
>  }
>  EXPORT_SYMBOL_GPL(dw_pcie_setup_rc);
>  
> +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 -ENOSPC;
> +
> +	if (!pci->pp.msg_res)
> +		return -ENOSPC;
> +
> +	atu.code = PCIE_MSG_CODE_PME_TURN_OFF;
> +	atu.routing = PCIE_MSG_TYPE_R_BC;
> +	atu.type = PCIE_ATU_TYPE_MSG;
> +	atu.size = resource_size(pci->pp.msg_res);
> +	atu.index = pci->pp.msg_atu_index;
> +
> +	atu.cpu_addr = pci->pp.msg_res->start;
> +
> +	ret = dw_pcie_prog_outbound_atu(pci, &atu);
> +	if (ret)
> +		return ret;
> +
> +	mem = ioremap(atu.cpu_addr, pci->region_align);
> +	if (!mem)
> +		return -ENOMEM;
> +
> +	/* A dummy write is converted to a Msg TLP */
> +	writel(0, mem);
> +
> +	iounmap(mem);
> +
> +	return 0;
> +}
> +
>  int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>  {
>  	u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
>  	u32 val;
> -	int ret;
> +	int ret = 0;
>  
>  	/*
>  	 * If L1SS is supported, then do not put the link into L2 as some
> @@ -854,10 +943,13 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>  	if (dw_pcie_get_ltssm(pci) <= DW_PCIE_LTSSM_DETECT_ACT)
>  		return 0;
>  
> -	if (!pci->pp.ops->pme_turn_off)
> -		return 0;
> +	if (pci->pp.ops->pme_turn_off)
> +		pci->pp.ops->pme_turn_off(&pci->pp);
> +	else
> +		ret = dw_pcie_pme_turn_off(pci);
>  
> -	pci->pp.ops->pme_turn_off(&pci->pp);
> +	if (ret)
> +		return ret;
>  
>  	ret = read_poll_timeout(dw_pcie_get_ltssm, val, val == DW_PCIE_LTSSM_L2_IDLE,
>  				PCIE_PME_TO_L2_TIMEOUT_US/10,
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 703b50bc5e0f1..dca5de4c6e877 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -341,6 +341,9 @@ struct dw_pcie_rp {
>  	struct pci_host_bridge  *bridge;
>  	raw_spinlock_t		lock;
>  	DECLARE_BITMAP(msi_irq_in_use, MAX_MSI_IRQS);
> +	bool			use_atu_msg;
> +	int			msg_atu_index;
> +	struct resource		*msg_res;
>  };
>  
>  struct dw_pcie_ep_ops {
> 
> -- 
> 2.34.1
> 

-- 
மணிவண்ணன் சதாசிவம்