linux-kernel - Re: [PATCH v2 4/4] PCI: brcmstb: Disable L0s component of ASPM if requested

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Date:   Tue, 05 May 2020 15:31:32 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Jim Quinlan <james.quinlan@...adcom.com>
Cc:     "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        Rob Herring <robh@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        "open list:PCI NATIVE HOST BRIDGE AND ENDPOINT DRIVERS" 
        <linux-pci@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v2 4/4] PCI: brcmstb: Disable L0s component of ASPM if
 requested

On Fri, 2020-05-01 at 10:28 -0400, Jim Quinlan wrote:
> From: Jim Quinlan <jquinlan@...adcom.com>
> 
> Some informal internal experiments has shown that the BrcmSTB ASPM L0s
> savings may introduce an undesirable noise signal on some customers'
> boards.  In addition, L0s was found lacking in realized power savings,
> especially relative to the L1 ASPM component.  This is BrcmSTB's
> experience and may not hold for others.  At any rate, if the
> 'aspm-no-l0s' property is present L0s will be disabled.
> 
> Signed-off-by: Jim Quinlan <jquinlan@...adcom.com>
> Acked-by: Florian Fainelli <f.fainelli@...il.com>

Modulo the new generic dt property:

Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>

Regards,
Nicolas

> ---
>  drivers/pci/controller/pcie-brcmstb.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/pcie-brcmstb.c
> b/drivers/pci/controller/pcie-brcmstb.c
> index 5b0dec5971b8..73020b4ff090 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
> @@ -41,6 +41,9 @@
>  #define PCIE_RC_CFG_PRIV1_ID_VAL3			0x043c
>  #define  PCIE_RC_CFG_PRIV1_ID_VAL3_CLASS_CODE_MASK	0xffffff
>  
> +#define PCIE_RC_CFG_PRIV1_LINK_CAPABILITY			0x04dc
> +#define  PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_ASPM_SUPPORT_MASK	0xc00
> +
>  #define PCIE_RC_DL_MDIO_ADDR				0x1100
>  #define PCIE_RC_DL_MDIO_WR_DATA				0x1104
>  #define PCIE_RC_DL_MDIO_RD_DATA				0x1108
> @@ -693,7 +696,7 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
>  	int num_out_wins = 0;
>  	u16 nlw, cls, lnksta;
>  	int i, ret;
> -	u32 tmp;
> +	u32 tmp, aspm_support;
>  
>  	/* Reset the bridge */
>  	brcm_pcie_bridge_sw_init_set(pcie, 1);
> @@ -803,6 +806,15 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
>  		num_out_wins++;
>  	}
>  
> +	/* Don't advertise L0s capability if 'aspm-no-l0s' */
> +	aspm_support = PCIE_LINK_STATE_L1;
> +	if (!of_property_read_bool(pcie->np, "aspm-no-l0s"))
> +		aspm_support |= PCIE_LINK_STATE_L0S;
> +	tmp = readl(base + PCIE_RC_CFG_PRIV1_LINK_CAPABILITY);
> +	u32p_replace_bits(&tmp, aspm_support,
> +		PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_ASPM_SUPPORT_MASK);
> +	writel(tmp, base + PCIE_RC_CFG_PRIV1_LINK_CAPABILITY);
> +
>  	/*
>  	 * For config space accesses on the RC, show the right class for
>  	 * a PCIe-PCIe bridge (the default setting is to be EP mode).


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