netdev - Re: [PATCH] net: bcmgenet: Reset RBUF on first open

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Date: Tue, 5 Mar 2024 07:13:21 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Doug Berger <opendmb@...il.com>
Cc: Florian Fainelli <florian.fainelli@...adcom.com>, Maarten Vanraes
 <maarten@...il.be>, netdev@...r.kernel.org, Broadcom internal kernel review
 list <bcm-kernel-feedback-list@...adcom.com>, Phil Elwell
 <phil@...pberrypi.com>
Subject: Re: [PATCH] net: bcmgenet: Reset RBUF on first open

On Mon, 26 Feb 2024 15:13:57 -0800 Doug Berger wrote:
> I agree that the Linux driver expects the GENET core to be in a "quasi 
> power-on-reset state" and it seems likely that in both Maxime's case and 
> the one identified here that is not the case. It would appear that the 
> Raspberry Pi bootloader and/or "firmware" are likely not disabling the 
> GENET receiver after loading the kernel image and before invoking the 
> kernel. They may be disabling the DMA, but that is insufficient since 
> any received data would likely overflow the RBUF leaving it in a "bad" 
> state which this patch apparently improves.
> 
> So it seems likely these issues are caused by improper 
> bootloader/firmware behavior.
> 
> That said, I suppose it would be nice if the driver were more robust. 
> However, we both know how finicky the receive path of the GENET core can 
> be about its initialization. Therefore, I am unwilling to "bless" this 
> change for upstream without more due diligence on our side.

The patch has minor formatting issues (using spaces to indent).
Once you've gain sufficient confidence that it doesn't cause issues -
please mend that and repost.
-- 
pw-bot: cr