From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2238C61DA4 for ; Wed, 22 Feb 2023 13:04:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231267AbjBVND6 (ORCPT ); Wed, 22 Feb 2023 08:03:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57046 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231149AbjBVND5 (ORCPT ); Wed, 22 Feb 2023 08:03:57 -0500 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7EF5A367CE; Wed, 22 Feb 2023 05:03:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=lM2W4JHS4uIFqBCnrz5vEgMwJ69cUYbi0tQ+lBrQUHA=; b=nA5YDOWn6Im8Lj9qYlwt8b7258 EdZi/lWVNfXDJcucnrGASy289rFyz0CtrIg9ph0D/QieQZoaxMHt61x9ykpS+CCdS4TEshZlyyKcM JrGpB9un2GXOCQQ1fCQLK5URJqZsgZgu4ixhogO4BTwhLbOwqtcemFVw3gyLfSMXXcYnCWY72Ajo5 qH588p5N9ACCyA5m062gsPdh3Fr/BZkeeWcxqGEby6LLDLxg2QEGuh6MRIp+DR6DY3mnMG4pESPd8 gA2pJtEOaLt7zAX39G2UVKUfCmzoxChE6tQ9g2UB/PCsCKnWSauJCt8x4MmfVTw7K/aBjniw8rYNX DJUG/OjA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:47156) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1pUomi-0006z8-CJ; Wed, 22 Feb 2023 13:03:48 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1pUomh-0003Dz-8V; Wed, 22 Feb 2023 13:03:47 +0000 Date: Wed, 22 Feb 2023 13:03:47 +0000 From: "Russell King (Oracle)" To: Marek Vasut Cc: netdev@vger.kernel.org, "David S. Miller" , Andrew Lunn , Arun Ramadoss , Eric Dumazet , Florian Fainelli , Jakub Kicinski , Paolo Abeni , UNGLinuxDriver@microchip.com, Vladimir Oltean , Woojung Huh , stable@vger.kernel.org Subject: Re: [PATCH] net: dsa: microchip: Fix gigabit set and get function for KSZ87xx Message-ID: References: <20230222031738.189025-1-marex@denx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Russell King (Oracle) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Feb 22, 2023 at 12:50:07PM +0000, Russell King (Oracle) wrote: > On Wed, Feb 22, 2023 at 04:17:38AM +0100, Marek Vasut wrote: > > diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c > > index 729b36eeb2c46..7fc2155d93d6e 100644 > > --- a/drivers/net/dsa/microchip/ksz_common.c > > +++ b/drivers/net/dsa/microchip/ksz_common.c > > @@ -319,7 +319,7 @@ static const u16 ksz8795_regs[] = { > > [S_BROADCAST_CTRL] = 0x06, > > [S_MULTICAST_CTRL] = 0x04, > > [P_XMII_CTRL_0] = 0x06, > > - [P_XMII_CTRL_1] = 0x56, > > + [P_XMII_CTRL_1] = 0x06, > > Looking at this driver, I have to say that it looks utterly vile > from the point of view of being sure that it is correct, and I > think this patch illustrates why. > > You mention you're using a KSZ8794. This uses the ksz8795_regs > array, and ksz8_dev_ops. You claim this is about the P_GMII_1GBIT_M > bit, which is bit 6. > > This bit is accessed only by ksz_get_gbit() and ksz_set_gbit(). > > Firstly, ksz_set_gbit() is only called from ksz_port_set_xmii_speed(), > which is only called from ksz9477_phylink_mac_link_up(). This is only > referenced by ksz9477_dev_ops and lan937x_dev_ops, but not ksz8_dev_ops. > Therefore, ksz_set_gbit() is not called for KSZ8794. > > ksz_get_gbit() is only referenced by ksz9477.c in > ksz9477_get_interface(), called only by ksz9477_config_cpu_port(). > This is only referenced by ksz9477_dev_ops, but not ksz8_dev_ops. > > Therefore, my conclusion is that neither of the ksz_*_gbit() > functions are called on KSZ8794, and thus your change has no effect > on the driver's use of P_GMII_1GBIT_M - I think if you put some > debugging printk()s into both ksz_*_gbit() functions, it'll prove > that. > > There's other places that P_XMII_CTRL_1 is accessed - ksz_set_xmii() > and ksz_get_xmii(). These look at the P_MII_SEL_M, P_RGMII_ID_IG_ENABLE > and P_RGMII_ID_EG_ENABLE bits - bits 0, 1, 3 and 4. > > ksz_get_xmii() is only called by ksz9477_get_interface(), which we've > already looked at above as not being called. > > ksz_set_xmii() is only called by ksz_phylink_mac_config(), which is > always called irrespective of the KSZ chip. > > Now, let's look at functions that access P_XMII_CTRL_0. These are > ksz_set_100_10mbit() and ksz_duplex_flowctrl(). The former > accesses bit P_MII_100MBIT_M, which is bit 4. The latter looks at > bits 6, bit 5, and possibly bit 3 depending on the masks being used. > KSZ8795 uses ksz8795_masks, which omits bit 3, so bits 5 and 6. > Note... bit 6 is also P_GMII_1GBIT_M. So if ksz_duplex_flowctrl() > is ever called for the KSZ8795, then we have a situation where > the P_GMII_1GBIT_M will be manipulated. > > ksz_set_100_10mbit() is only called from ksz_port_set_xmii_speed(), > which we've established won't be called. > > ksz_duplex_flowctrl() is only called from ksz9477_phylink_mac_link_up() > which we've also established won't be called. > > So, as far as I can see, P_XMII_CTRL_0 won't be accessed on this > device. > > Now, what about other KSZ devices - I've analysed this for the KSZ8795, > but what about any of the others which use this register table? It > looks to me like those that use ksz8795_regs[] all use ksz8_dev_ops > and the same masks and bitvals, so they should be the same. > > That is a hell of a lot of work to prove that setting both > P_XMII_CTRL_0 and P_XMII_CTRL_1 to point at the same register is > in fact safe. Given the number of registers, the masks, and bitval > arrays, doing this to prove every combination and then analysing > the code is utterly impractical - and thus why I label this driver > as "vile". Is there really no better option to these register > arrays, bitval arrays and mask arrays - something that makes it > easier to review and prove correctness? > > I'm not going to give a reviewed-by for this, because... I could > have made a mistake in the above analysis given the vile nature > of this driver. However, I should add that - as a result of neither ksz_*_gbit() functions being used, I consider at least the subject line to be rather misleading! While it may be something that you spotted, I suspect the other bits that are actually written are more the issue you're fixing. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!