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

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Message-ID: <51eff793-2b72-4e1c-a86e-149f17d08279@suse.de>
Date: Wed, 21 Aug 2024 02:38:07 +0300
From: Stanimir Varbanov <svarbanov@...e.de>
To: Florian Fainelli <florian.fainelli@...adcom.com>,
 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: 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

Hi Florian,

On 8/19/24 22:07, Florian Fainelli wrote:
> 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).

Good to know that 9 is not the proper reset line, thank you.

Unfortunately, I'm unable to make it work with the proper reset line (32).

> 
> 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

No idea why downstream RPi kernel does not use swinit reset.

> this will work without.

If I do not populate swinit in PCIe DT node it works i.e. PCI
enumeration is working and RP1 south-bridge is functional.

~Stan