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[193.12.47.89]) by smtp.gmail.com with ESMTPSA id j20sm438526lfu.199.2021.11.04.04.17.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Nov 2021 04:17:55 -0700 (PDT) From: Tobias Waldekranz To: Andrew Lunn , Grygorii Strashko Cc: "Russell King (Oracle)" , "David S. Miller" , netdev@vger.kernel.org, Jakub Kicinski , Heiner Kallweit , Florian Fainelli , linux-kernel@vger.kernel.org, Vignesh Raghavendra , Sean Anderson Subject: Re: [RFC PATCH] net: phy/mdio: enable mmd indirect access through phy_mii_ioctl() In-Reply-To: References: <828e2d69-be15-fe69-48d8-9cfc29c4e76e@ti.com> <8d24c421-064c-9fee-577a-cbbf089cdf33@ti.com> <01a0ebf9-5d3f-e886-4072-acb9bf418b12@ti.com> Date: Thu, 04 Nov 2021 12:17:47 +0100 Message-ID: <87pmrgjhk4.fsf@waldekranz.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Nov 03, 2021 at 20:36, Andrew Lunn wrote: > On Wed, Nov 03, 2021 at 08:42:07PM +0200, Grygorii Strashko wrote: >> >> >> On 03/11/2021 02:27, Andrew Lunn wrote: >> > > > What i find interesting is that you and the other resent requester are >> > > > using the same user space tool. If you implement C45 over C22 in that >> > > > tool, you get your solution, and it will work for older kernels as >> > > > well. Also, given the diverse implementations of this IOTCL, it >> > > > probably works for more drivers than just those using phy_mii_ioctl(). >> > > >> > > Do you mean change uapi, like >> > > add mdio_phy_id_is_c45_over_c22() and >> > > flag #define MDIO_PHY_ID_C45_OVER_C22 0x4000? >> > >> > No, i mean user space implements C45 over C22. Make phytool write >> > MII_MMD_CTRL and MII_MMD_DATA to perform a C45 over C22. >> >> Now I give up - as mentioned there is now way to sync User space vs Kernel >> MMD transactions and so no way to get trusted results. Except that there is a way: https://github.com/wkz/mdio-tools I can see that Sean has already mentioned it in the other branch of the thread (thanks for the plug :)). I have posted it to netdev before: https://lore.kernel.org/netdev/C42DZQLTPHM5.2THDSRK84BI3T@wkz-x280/ It allows you to send an entire "MDIO program" to the kernel, where mdio-netlink will (1) lock the bus, (2) run your program in a small VM, and (3) unlock the bus. There are currently two programs in the project: - `mdio`: A basic register peek/poke program that uses the mdio-netlink module in the kernel to do its thing. The source is structured in such a way that custom access modes can be easily added. Today there are accessors for C22 PHYs, C45 MMDs, Marvell Alaska paged PHYs, Marvell LinkStreet switches, and XRS700x switches. - `mvls`: Specialized read-only debug tool for Marvell LinkStreet switches. This does _not_ rely on the mdio-netlink kernel module, instead it uses the standard devlink API. Let's you dump the VTU/ATU etc. You could easily add a new addressing mode to `mdio` to do C45-over-C22 accesses. Would that work for you Grygorii? > Except that it will probably work 99% of the time, which is enough for > a debug tool. Why though, why would we not build something that is rock solid? Ever since ce69e2162f15, the flood gates are open. Any vendor can implement mdio-netlink on their own, or just download mine. We are only punishing ourselves at this point. > phylib is pretty idle most of the time, it just polls > the PHY once a second to see if the link status has changed. And does > not poll at all if interrupts are wired up. And you can always do a > read three times and see if you get the same answer, or do a write > followed by a read to see if the write actually happened correctly, or > corrupted some other register. As a staunch opponent of Vendor SDKs myself, I get where you are coming from - really. I guess I just don't have the brain power to operate this kind of Rube Goldberg machinery and debug my problems at the same time. We have a mutex right there already, let's use it! I'll shut up now - I just had to make one final appeal :)