Re: [RFC PATCH 2/3] mwifiex: pcie: add reset_d3cold quirk for Surface gen4+ devices

[Bjorn Helgaas]

On Sat, May 22, 2021 at 03:18:26PM +0200, Jonas Dreßler wrote:
> From: Tsuchiya Yuto <kitakar@xxxxxxxxx>
> 
> To reset mwifiex on Surface gen4+ (Pro 4 or later gen) devices, it
> seems that putting the wifi device into D3cold is required according
> to errata.inf file on Windows installation (Windows/INF/errata.inf).
> 
> This patch adds a function that performs power-cycle (put into D3cold
> then D0) and call the function at the end of reset_prepare().
> 
> Note: Need to also reset the parent device (bridge) of wifi on SB1;
> it might be because the bridge of wifi always reports it's in D3hot.
> When I tried to reset only the wifi device (not touching parent), it gave
> the following error and the reset failed:
> 
>     acpi device:4b: Cannot transition to power state D0 for parent in D3hot
>     mwifiex_pcie 0000:03:00.0: can't change power state from D3cold to D0 (config space inaccessible)
> 
> Signed-off-by: Tsuchiya Yuto <kitakar@xxxxxxxxx>
> Signed-off-by: Jonas Dreßler <verdre@xxxxxxx>
> ---
>  drivers/net/wireless/marvell/mwifiex/pcie.c   |   7 +
>  .../wireless/marvell/mwifiex/pcie_quirks.c    | 123 ++++++++++++++++++
>  .../wireless/marvell/mwifiex/pcie_quirks.h    |   3 +
>  3 files changed, 133 insertions(+)
> 
> diff --git a/drivers/net/wireless/marvell/mwifiex/pcie.c b/drivers/net/wireless/marvell/mwifiex/pcie.c
> index 02fdce926de5..d9acfea395ad 100644
> --- a/drivers/net/wireless/marvell/mwifiex/pcie.c
> +++ b/drivers/net/wireless/marvell/mwifiex/pcie.c
> @@ -528,6 +528,13 @@ static void mwifiex_pcie_reset_prepare(struct pci_dev *pdev)
>  	mwifiex_shutdown_sw(adapter);
>  	clear_bit(MWIFIEX_IFACE_WORK_DEVICE_DUMP, &card->work_flags);
>  	clear_bit(MWIFIEX_IFACE_WORK_CARD_RESET, &card->work_flags);
> +
> +	/* For Surface gen4+ devices, we need to put wifi into D3cold right
> +	 * before performing FLR

This comment seems incorrect or at least incomplete.  When the device
is in D3cold, it isn't powered at all, so you can't do anything with
it, including FLR.  But maybe you meant that you need to put it in
D3cold and back to D0 before doing an FLR.  That would work.  But in
that case, there's no point in an FLR because the power cycle has
already reset more than the FLR will.

Bjorn