linux-kernel - Re: [PATCH v2 -next 07/11] PCI: brcmstb: Avoid turn off of bridge reset

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Message-ID: <b41afb62-8a89-4c9d-8462-f4c5574eac7a@broadcom.com>
Date: Tue, 10 Sep 2024 10:03:32 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Stanimir Varbanov <svarbanov@...e.de>, 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>
Cc: Thomas Gleixner <tglx@...utronix.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, 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 v2 -next 07/11] PCI: brcmstb: Avoid turn off of bridge
 reset

On 9/10/24 08:18, Stanimir Varbanov wrote:
> On brcm_pcie_turn_off avoid shutdown of bridge reset.
> 
> Signed-off-by: Stanimir Varbanov <svarbanov@...e.de>
> ---
>   drivers/pci/controller/pcie-brcmstb.c | 14 ++++++++++++--
>   1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> index d78f33b33884..185ccf7fe86a 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
> @@ -234,10 +234,17 @@ struct inbound_win {
>   	u64 cpu_addr;
>   };
>   
> +/*
> + * Shutting down this bridge on pcie1 means accesses to rescal block
> + * will hang the chip if another RC wants to assert/deassert rescal.
> + */

Maybe a slightly more detailed comment saying that 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).

Thanks!
-- 
Florian