linux-kernel - Re: [PATCH 04/12] PCI: dwc: Disable outbound windows for controllers with iATU

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Message-ID: <20220324090514.GD2854@thinkpad>
Date:   Thu, 24 Mar 2022 14:35:14 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Frank Li <Frank.Li@....com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/12] PCI: dwc: Disable outbound windows for controllers
 with iATU

On Thu, Mar 24, 2022 at 04:25:15AM +0300, Serge Semin wrote:
> In accordance with the dw_pcie_setup_rc() method semantics and judging by
> what the comment added in commit dd193929d91e ("PCI: designware: Explain
> why we don't program ATU for some platforms") states there are DWC
> PCIe-available platforms like Keystone (pci-keystone.c) or Amazon's
> Annapurna Labs (pcie-al.c) which don't have the DW PCIe internal ATU
> enabled and use it's own address translation approach implemented. In
> these cases at the very least there is no point in touching the DW PCIe
> iATU CSRs. Moreover depending on the vendor-specific address translation
> implementation it might be even erroneous. So let's move the iATU windows
> disabling procedure to being under the corresponding conditional statement
> clause thus performing that procedure only if the iATU is expected to be
> available on the platform.
> 
> Fixes: 458ad06c4cdd ("PCI: dwc: Ensure all outbound ATU windows are reset")
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Thanks,
Mani

> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index f89e6552139b..a048d88e0c30 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -566,7 +566,6 @@ static struct pci_ops dw_pcie_ops = {
>  
>  void dw_pcie_setup_rc(struct pcie_port *pp)
>  {
> -	int i;
>  	u32 val, ctrl, num_ctrls;
>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>  
> @@ -618,19 +617,22 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
>  		PCI_COMMAND_MASTER | PCI_COMMAND_SERR;
>  	dw_pcie_writel_dbi(pci, PCI_COMMAND, val);
>  
> -	/* Ensure all outbound windows are disabled so there are multiple matches */
> -	for (i = 0; i < pci->num_ob_windows; i++)
> -		dw_pcie_disable_atu(pci, i, DW_PCIE_REGION_OUTBOUND);
> -
>  	/*
>  	 * If the platform provides its own child bus config accesses, it means
>  	 * the platform uses its own address translation component rather than
>  	 * ATU, so we should not program the ATU here.
>  	 */
>  	if (pp->bridge->child_ops == &dw_child_pcie_ops) {
> -		int atu_idx = 0;
> +		int i, atu_idx = 0;
>  		struct resource_entry *entry;
>  
> +		/*
> +		 * Ensure all outbound windows are disabled so there are
> +		 * multiple matches
> +		 */
> +		for (i = 0; i < pci->num_ob_windows; i++)
> +			dw_pcie_disable_atu(pci, i, DW_PCIE_REGION_OUTBOUND);
> +
>  		/* Get last memory resource entry */
>  		resource_list_for_each_entry(entry, &pp->bridge->windows) {
>  			if (resource_type(entry->res) != IORESOURCE_MEM)
> -- 
> 2.35.1
>