Re: [PATCH] PCI: mediatek-gen3: Avoid PCIe resetting for Airoha EN7581 SoC

[Lorenzo Bianconi <lorenzo@kernel.org>]

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> On Mon, Sep 23, 2024 at 11:41:41AM +0200, AngeloGioacchino Del Regno wrote:
> > Il 20/09/24 10:26, Lorenzo Bianconi ha scritto:
> > > The PCIe controller available on the EN7581 SoC does not support reset
> > > via the following lines:
> > > - PCIE_MAC_RSTB
> > > - PCIE_PHY_RSTB
> > > - PCIE_BRG_RSTB
> > > - PCIE_PE_RSTB
> > > 
> > > Introduce the reset callback in order to avoid resetting the PCIe port
> > > for Airoha EN7581 SoC.
> > 
> > EN7581 doesn't support pulling up/down PERST#?!  That looks
> > definitely odd, as that signal is part of the PCI-Express CEM spec.
> > 
> > Besides, there's another PERST# assertion at
> > mtk_pcie_suspend_noirq()...
> 
> I agree, it doesn't smell right that this SoC doesn't have a way to
> assert PERST#.
> 
> The response at
> https://lore.kernel.org/r/SG2PR03MB63415DB5791C58C7EA69FF01FF682@SG2PR03MB6341.apcprd03.prod.outlook.com
> suggests that maybe there's a hardware defect that means asserting
> PERST# doesn't work correctly?  But surely firmware must have a way of
> asserting PERST#, at least at boot time.
> 
> If this is truly a hardware defect and we really can't assert PERST#,
> please say that this is a defect in the commit log so people don't
> think that lack of PERST# is an acceptable thing.

Hi Bjorn,

I do not have visibility on these hw details.
@Hui: any update on it?

Regards,
Lorenzo

> 
> Bjorn

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