linux-kernel - Re: [PATCH v3 06/11] PCI: brcmstb: Avoid turn off of bridge reset

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Message-ID: <20241014170105.GA611115@bhelgaas>
Date: Mon, 14 Oct 2024 12:01:05 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Stanimir Varbanov <svarbanov@...e.de>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rpi-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Thomas Gleixner <tglx@...utronix.de>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Jim Quinlan <jim2101024@...il.com>,
	Nicolas Saenz Julienne <nsaenz@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>, kw@...ux.com,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Andrea della Porta <andrea.porta@...e.com>,
	Phil Elwell <phil@...pberrypi.com>,
	Jonathan Bell <jonathan@...pberrypi.com>
Subject: Re: [PATCH v3 06/11] PCI: brcmstb: Avoid turn off of bridge reset

On Mon, Oct 14, 2024 at 04:07:05PM +0300, Stanimir Varbanov wrote:
> On PCIe turn off avoid shutdown of bridge reset,
> by introducing a quirk flag.

Can you include something here about *why* we need this change?  I
think the RESCAL comment below would be a good start.

I think this should be squashed with the next commit that adds the use
of CFG_QUIRK_AVOID_BRIDGE_SHUTDOWN.  Otherwise this commit doesn't
have an obvious reason.

> Signed-off-by: Stanimir Varbanov <svarbanov@...e.de>
> ---
> v2 -> v3:
>  - Added more descriptive comment on CFG_QUIRK_AVOID_BRIDGE_SHUTDOWN quirk.
> 
>  drivers/pci/controller/pcie-brcmstb.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> index b76c16287f37..757a1646d53c 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
> @@ -234,10 +234,20 @@ struct inbound_win {
>  	u64 cpu_addr;
>  };
>  
> +/*
> + * The RESCAL block is tied to PCIe controller #1, regardless of the number of
> + * controllers, and turning off PCIe controller #1 prevents access to the RESCAL
> + * register blocks, therefore not other controller can access this register
> + * space, and depending upon the bus fabric we may get a timeout (UBUS/GISB),
> + * or a hang (AXI).

s/not other/no other/

> + */
> +#define CFG_QUIRK_AVOID_BRIDGE_SHUTDOWN		BIT(0)
> +
>  struct pcie_cfg_data {
>  	const int *offsets;
>  	const enum pcie_soc_base soc_base;
>  	const bool has_phy;
> +	const u32 quirks;
>  	u8 num_inbound_wins;
>  	int (*perst_set)(struct brcm_pcie *pcie, u32 val);
>  	int (*bridge_sw_init_set)(struct brcm_pcie *pcie, u32 val);
> @@ -290,6 +300,7 @@ struct brcm_pcie {
>  	struct subdev_regulators *sr;
>  	bool			ep_wakeup_capable;
>  	bool			has_phy;
> +	u32			quirks;
>  	u8			num_inbound_wins;
>  };
>  
> @@ -1539,8 +1550,9 @@ static int brcm_pcie_turn_off(struct brcm_pcie *pcie)
>  	u32p_replace_bits(&tmp, 1, PCIE_MISC_HARD_PCIE_HARD_DEBUG_SERDES_IDDQ_MASK);
>  	writel(tmp, base + HARD_DEBUG(pcie));
>  
> -	/* Shutdown PCIe bridge */
> -	ret = pcie->bridge_sw_init_set(pcie, 1);
> +	if (!(pcie->quirks & CFG_QUIRK_AVOID_BRIDGE_SHUTDOWN))
> +		/* Shutdown PCIe bridge */
> +		ret = pcie->bridge_sw_init_set(pcie, 1);
>  
>  	return ret;
>  }
> @@ -1854,6 +1866,7 @@ static int brcm_pcie_probe(struct platform_device *pdev)
>  	pcie->perst_set = data->perst_set;
>  	pcie->bridge_sw_init_set = data->bridge_sw_init_set;
>  	pcie->has_phy = data->has_phy;
> +	pcie->quirks = data->quirks;
>  	pcie->num_inbound_wins = data->num_inbound_wins;
>  
>  	pcie->base = devm_platform_ioremap_resource(pdev, 0);
> -- 
> 2.43.0
>