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Date: Fri, 23 May 2025 07:33:16 +0200
From: Lukas Wunner <lukas@wunner.de>
To: Niklas Cassel <cassel@kernel.org>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
	Wilfred Mallawa <wilfred.mallawa@wdc.com>,
	Bjorn Helgaas <helgaas@kernel.org>,
	Damien Le Moal <dlemoal@kernel.org>, linux-pci@vger.kernel.org
Subject: Re: reset_slot() callback not respecting MPS config
Message-ID: <aDAInK0F0Qh7QTiw@wunner.de>
References: <aC9OrPAfpzB_A4K2@ryzen>
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In-Reply-To: <aC9OrPAfpzB_A4K2@ryzen>

On Thu, May 22, 2025 at 06:19:56PM +0200, Niklas Cassel wrote:
> As you know the reset_slot() callback patches were merged recently.
> 
> Wilfred and I (mostly Wilfred), have been debugging DMA issues after the
> reset_slot() callback has been invoked. The issue is reproduced when MPS
> configuration is set to performance, but might be applicable for other
> MPS configurations as well. The problem appears to be that reset_slot()
> feature does not respect/restore the MPS configuration.

The Device Control register (and thus the MPS setting) is saved via:

  pci_save_state()
    pci_save_pcie_state()

So either you're missing a call to pci_restore_state() after reset,
or you're missing a call to pci_save_state() after changing MPS,
or MPS is somehow overwritten after pci_restore_state().
Which one is it?

Thanks,

Lukas