linux-kernel - Re: [PATCH v2] PCI: mediatek-gen3: Assert MAC reset only if PHY reset also present

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Date: Thu, 29 Feb 2024 11:20:13 -0500
From: Nícolas F. R. A. Prado <nfraprado@...labora.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: linux-pci@...r.kernel.org, ryder.lee@...iatek.com,
	jianjun.wang@...iatek.com, lpieralisi@...nel.org, kw@...ux.com,
	robh@...nel.org, bhelgaas@...gle.com, p.zabel@...gutronix.de,
	matthias.bgg@...il.com, linux-mediatek@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kernel@...labora.com, wenst@...omium.org
Subject: Re: [PATCH v2] PCI: mediatek-gen3: Assert MAC reset only if PHY
 reset also present

On Thu, Feb 29, 2024 at 10:24:49AM +0100, AngeloGioacchino Del Regno wrote:
> Some SoCs have two PCI-Express controllers: in the case of MT8195,
> one of them is using a dedicated PHY, but the other uses a combo PHY
> that is shared with USB and in that case the PHY cannot be reset
> from the PCIe driver, or USB functionality will be unable to resume.
> 
> Resetting the PCIe MAC without also resetting the PHY will result in
> a full system lockup at PCIe resume time and the only option to
> resume operation is to hard reboot the system (with a PMIC cut-off).
> 
> To resolve this issue, check if we've got both a PHY and a MAC reset
> and, if not, never assert resets at PM suspend time: in that case,
> the link is still getting powered down as both the clocks and the
> power domains will go down anyway.
> 
> Fixes: d537dc125f07 ("PCI: mediatek-gen3: Add system PM support")
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

With this applied resume finally works on MT8195-Tomato! And I no longer see the
errors I mentioned in [1]. So,

Tested-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>

Thanks,
Nícolas

[1] https://lore.kernel.org/all/d8cfb804-e47a-471c-8bc0-e974ee045655@notapiano/