linux-kernel - Re: [PATCH] PCI: mediatek-gen3: Assert MAC Reset only for a delay during PM suspend sequence

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Message-ID: <6c132018714402d0a46fb8b59c862fb7f96a77f8.camel@collabora.com>
Date: Thu, 10 Jul 2025 11:06:54 -0400
From: Nícolas "F. R. A. Prado" <nfraprado@...labora.com>
To: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>, Ryder Lee	
 <ryder.lee@...iatek.com>, Jianjun Wang <jianjun.wang@...iatek.com>, Lorenzo
 Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczyński
 <kwilczynski@...nel.org>,  Manivannan Sadhasivam	 <mani@...nel.org>, Rob
 Herring <robh@...nel.org>, Bjorn Helgaas	 <bhelgaas@...gle.com>, Philipp
 Zabel <p.zabel@...gutronix.de>, Matthias Brugger	 <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno	 <angelogioacchino.delregno@...labora.com>
Cc: kernel@...labora.com, linux-pci@...r.kernel.org, 
	linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] PCI: mediatek-gen3: Assert MAC Reset only for a delay
 during PM suspend sequence

On Wed, 2025-07-09 at 17:42 +0200, Louis-Alexis Eyraud wrote:
> In the pcie-mediatek-gen3 driver, the PM suspend callback function
> powers down the PCIE link to stop the clocks and PHY and also assert
> the MAC and PHY resets.
> 
> On MT8195 SoC, asserting the MAC reset for PCIe port 0 during suspend
> sequence and letting it asserted leads the system to hang during
> resume
> sequence because the PCIE link remains down after powering it up:
> ```
> mtk-pcie-gen3 112f0000.pcie: PCIe link down, current LTSSM state:
>   detect.quiet (0x0)
> mtk-pcie-gen3 112f0000.pcie: PM: dpm_run_callback():
> genpd_resume_noirq
>   returns -110
> mtk-pcie-gen3 112f0000.pcie: PM: failed to resume noirq: error -110
> ```
> Deasserting it before suspend sequence is completed, allows the
> system
> to resume properly.
> 
> So, add in the mtk_pcie_power_down function a flag parameter to say
> if the
> device is being suspended and in this case, make the MAC reset be
> deasserted after PCIE_MTK_RESET_TIME_US (=10us) delay.
> 
> Fixes: d537dc125f07 ("PCI: mediatek-gen3: Add system PM support")
> Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>

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

-- 
Thanks,

Nícolas