From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: DKIM-Filter: OpenDKIM Filter v2.11.0 smtp4.osuosl.org 6703742408 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp4.osuosl.org 32870423F8 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1657241048; bh=EC7a4jTfAaizoRSMF4FsVpM10jc1Vx60by0MKMOikKI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=J7buxAjoy+adEYbK2ndgRVkdH/bRZQd1xQJ83dKqMYPLqzO7K8SohPXucoAmj7lJw lXlK98vnwsMtyUs6cqJvdncgZSM+u8iWNEd84GaJxGEb8JwmJznOQ8diA8yX3EE+9t AyBc2jtDAHiy/c9qalzH/C4zpxEfR44rctLToIM/H+o6DzxW+shjErAqPIZ51BH2Tj w3PhcIgxKUGzp6rfEjTCNkv8zm+iHrtWRB+8L8NEZ7Mv9xOAjzyEzGVOLdus18aNvi qFBhYl1bIalHBXubutm/9Fbfkaocgls6Zfa3BLkpbMVdpgT4B7+bPE8Q+LLXcKle9S rXNUZKZHDb9sw== Date: Thu, 7 Jul 2022 17:43:58 -0700 From: Jakub Kicinski Message-ID: <20220707174358.3b1b804a@kernel.org> In-Reply-To: <20220707102836.u7ig6rr2664mcrlf@skbuf> References: <20220706122502.1521819-1-netdev@kapio-technology.com> <20220707102836.u7ig6rr2664mcrlf@skbuf> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Bridge] [PATCH net-next 1/1] net: dsa: mv88e6xxx: allow reading FID when handling ATU violations List-Id: Linux Ethernet Bridging List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Hans Schultz Cc: Ivan Vecera , Andrew Lunn , Florian Fainelli , Jiri Pirko , Daniel Borkmann , netdev@vger.kernel.org, Nikolay Aleksandrov , bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Ido Schimmel , Vivien Didelot , Eric Dumazet , linux-kselftest@vger.kernel.org, Roopa Prabhu , Paolo Abeni , Vladimir Oltean , Shuah Khan , davem@davemloft.net On Thu, 7 Jul 2022 13:28:36 +0300 Vladimir Oltean wrote: > Make no mistake, the existing code doesn't disallow reading back the FID > during an ATU Get/Clear Violation operation, and your patch isn't > "allowing" something that wasn't disallowed. > > The documentation for the ATU FID register says that its contents is > ignored before the operation starts, and it contains the returned ATU > entry's FID after the operation completes. > > So the change simply says: don't bother to write the ATU FID register > with zero, it doesn't matter what this contains. This is probably true, > but the patch needs to do what's written on the box. > > Please note that this only even matters at all for switches with > mv88e6xxx_num_databases(chip) > 256, where MV88E6352_G1_ATU_FID is a > dedicated register which this patch avoids writing. For other switches, > the FID is embedded within MV88E6XXX_G1_ATU_CTL or MV88E6XXX_G1_ATU_OP. > So _practically_, for those switches, you are still emitting the > GET_CLR_VIOLATION ATU op with a FID of 0 whether you like it or not, and > this patch introduces a (most likely irrelevant) discrepancy between the > access methods for various switches. > > Please note that this observation is relevant for your future changes to > read back the FID too. As I said here: > https://patchwork.kernel.org/project/netdevbpf/patch/20220524152144.40527-4-schultz.hans+netdev@gmail.com/#24912482 > you can't just assume that the FID lies within the MV88E6352_G1_ATU_FID > register, just look at the way it is packed within mv88e6xxx_g1_atu_op(). > You'll need to unpack it in the same way. I reckon it'll be useful to render some of this info into the commit message and adjust the subject so marking Changes Requested.