netdev - Re: [PATCH net 1/3] mlxsw: pci: Fix driver initialization with Spectrum-4

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Date: Wed, 19 Jun 2024 15:50:40 +0100
From: Simon Horman <horms@...nel.org>
To: Petr Machata <petrm@...dia.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, Ido Schimmel <idosch@...dia.com>,
	mlxsw@...dia.com, Maksym Yaremchuk <maksymy@...dia.com>
Subject: Re: [PATCH net 1/3] mlxsw: pci: Fix driver initialization with
 Spectrum-4

On Mon, Jun 17, 2024 at 06:56:00PM +0200, Petr Machata wrote:
> From: Ido Schimmel <idosch@...dia.com>
> 
> Cited commit added support for a new reset flow ("all reset") which is
> deeper than the existing reset flow ("software reset") and allows the
> device's PCI firmware to be upgraded.
> 
> In the new flow the driver first tells the firmware that "all reset" is
> required by issuing a new reset command (i.e., MRSR.command=6) and then
> triggers the reset by having the PCI core issue a secondary bus reset
> (SBR).
> 
> However, due to a race condition in the device's firmware the device is
> not always able to recover from this reset, resulting in initialization
> failures [1].
> 
> New firmware versions include a fix for the bug and advertise it using a
> new capability bit in the Management Capabilities Mask (MCAM) register.
> 
> Avoid initialization failures by reading the new capability bit and
> triggering the new reset flow only if the bit is set. If the bit is not
> set, trigger a normal PCI hot reset by skipping the call to the
> Management Reset and Shutdown Register (MRSR).
> 
> Normal PCI hot reset is weaker than "all reset", but it results in a
> fully operational driver and allows users to flash a new firmware, if
> they want to.
> 
> [1]
> mlxsw_spectrum4 0000:01:00.0: not ready 1023ms after bus reset; waiting
> mlxsw_spectrum4 0000:01:00.0: not ready 2047ms after bus reset; waiting
> mlxsw_spectrum4 0000:01:00.0: not ready 4095ms after bus reset; waiting
> mlxsw_spectrum4 0000:01:00.0: not ready 8191ms after bus reset; waiting
> mlxsw_spectrum4 0000:01:00.0: not ready 16383ms after bus reset; waiting
> mlxsw_spectrum4 0000:01:00.0: not ready 32767ms after bus reset; waiting
> mlxsw_spectrum4 0000:01:00.0: not ready 65535ms after bus reset; giving up
> mlxsw_spectrum4 0000:01:00.0: PCI function reset failed with -25
> mlxsw_spectrum4 0000:01:00.0: cannot register bus device
> mlxsw_spectrum4: probe of 0000:01:00.0 failed with error -25
> 
> Fixes: f257c73e5356 ("mlxsw: pci: Add support for new reset flow")
> Cc: Simon Horman <horms@...nel.org>
> Reported-by: Maksym Yaremchuk <maksymy@...dia.com>
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> Tested-by: Maksym Yaremchuk <maksymy@...dia.com>
> Signed-off-by: Petr Machata <petrm@...dia.com>

Reviewed-by: Simon Horman <horms@...nel.org>