linux-kernel - Re: [PATCH v6 05/13] PCI: brcmstb: Use bridge reset if available

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Message-ID: <2fb74b23-a862-4b1c-b1e1-a3e3abc4571b@broadcom.com>
Date: Mon, 19 Aug 2024 12:07:20 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Stanimir Varbanov <svarbanov@...e.de>,
 Jim Quinlan <james.quinlan@...adcom.com>, linux-pci@...r.kernel.org,
 Nicolas Saenz Julienne <nsaenz@...nel.org>,
 Bjorn Helgaas <bhelgaas@...gle.com>,
 Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
 Cyril Brulebois <kibi@...ian.org>,
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 Krzysztof Kozlowski <krzk@...nel.org>,
 bcm-kernel-feedback-list@...adcom.com, jim2101024@...il.com
Cc: Florian Fainelli <florian.fainelli@...adcom.com>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Krzysztof Wilczyński <kw@...ux.com>,
 Rob Herring <robh@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>,
 "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
 <linux-rpi-kernel@...ts.infradead.org>,
 "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
 <linux-arm-kernel@...ts.infradead.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 05/13] PCI: brcmstb: Use bridge reset if available

On 8/17/24 10:41, Stanimir Varbanov wrote:
> Hi Jim,
> 
> On 8/16/24 01:57, Jim Quinlan wrote:
>> The 7712 SOC has a bridge reset which can be described in the device tree.
>> Use it if present.  Otherwise, continue to use the legacy method to reset
>> the bridge.
>>
>> Signed-off-by: Jim Quinlan <james.quinlan@...adcom.com>
>> ---
>>   drivers/pci/controller/pcie-brcmstb.c | 24 +++++++++++++++++++-----
>>   1 file changed, 19 insertions(+), 5 deletions(-)
> 
> Reviewed-by: Stanimir Varbanov <svarbanov@...e.de>
> 
> One problem though on RPi5 (bcm2712).
> 
> With this series applied + my WIP patches for enablement of PCIe on
> bcm2712 when enable the pcie1 and pcie2 root ports in dts, I see kernel
> boot stuck on pcie2 enumeration and I have to add this [1] to make it
> work again.
> 
> Some more info about resets used:
> 
> pcie0 @ 100000:
> 	resets = <&bcm_reset 5>, <&bcm_reset 42>, <&pcie_rescal>;
> 	reset-names = "swinit", "bridge", "rescal";
> 
> pcie1 @ 110000:
> 	resets = <&bcm_reset 7>, <&bcm_reset 43>, <&pcie_rescal>;
> 	reset-names = "swinit", "bridge", "rescal";
> 
> pcie2 @ 120000:
> 	resets = <&bcm_reset 9>, <&bcm_reset 44>, <&pcie_rescal>;
> 	reset-names = "swinit", "bridge", "rescal"; >
> 
> I changed "swinit" reset for pcie2 to <&bcm_reset 9> (it is 32 in
> downstream rpi kernel) because otherwise I'm unable to enumerate RP1
> south bridge at all.

The value 9 is unused, so I suppose it does not really hurt to use it, 
but it is also unlikely to achieve what you desire. 32 is the correct 
value since pcie2_sw_init is bit 0 within SW_INIT_1 (second bank of resets).

The file link you provided appears to be lacking support for the 
"swinit" reset line, is that intentional? I don't think you can assume 
this will work without.
-- 
Florian