netdev - Re: [PATCH net 1/2] Revert "can: m_can: pci: use custom bit timings for Elkhart Lake"

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Message-ID: <20220513102145.748db22c@kernel.org>
Date:   Fri, 13 May 2022 10:21:45 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        linux-can@...r.kernel.org, kernel@...gutronix.de,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Chee Hou Ong <chee.houx.ong@...el.com>,
        Aman Kumar <aman.kumar@...el.com>,
        Pallavi Kumari <kumari.pallavi@...el.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH net 1/2] Revert "can: m_can: pci: use custom bit timings
 for Elkhart Lake"

On Fri, 13 May 2022 15:08:18 +0200 Marc Kleine-Budde wrote:
> From: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
> 
> This reverts commit 0e8ffdf3b86dfd44b651f91b12fcae76c25c453b.
> 
> Commit 0e8ffdf3b86d ("can: m_can: pci: use custom bit timings for
> Elkhart Lake") broke the test case using bitrate switching.
> 
> | ip link set can0 up type can bitrate 500000 dbitrate 4000000 fd on
> | ip link set can1 up type can bitrate 500000 dbitrate 4000000 fd on
> | candump can0 &
> | cangen can1 -I 0x800 -L 64 -e -fb \
> |     -D 11223344deadbeef55667788feedf00daabbccdd44332211 -n 1 -v -v
> 
> Above commit does everything correctly according to the datasheet.
> However datasheet wasn't correct.
> 
> I got confirmation from hardware engineers that the actual CAN
> hardware on Intel Elkhart Lake is based on M_CAN version v3.2.0.
> Datasheet was mirroring values from an another specification which was
> based on earlier M_CAN version leading to wrong bit timings.
> 
> Therefore revert the commit and switch back to common bit timings.
> 
> Fixes: 0e8ffdf3b86d ("can: m_can: pci: use custom bit timings for Elkhart Lake")
> Link: https://lore.kernel.org/all/20220512124144.536850-1-jarkko.nikula@linux.intel.com
> Signed-off-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
> Reported-by: Chee Hou Ong <chee.houx.ong@...el.com>
> Reported-by: Aman Kumar <aman.kumar@...el.com>
> Reported-by: Pallavi Kumari <kumari.pallavi@...el.com>
> Cc: <stable@...r.kernel.org> # v5.16+
> Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>

nit: the hash in the fixes tag should be:

Fixes: ea4c1787685d ("can: m_can: pci: use custom bit timings for Elkhart Lake")

Do you want to respin or is the can tree non-rebasable?