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Subject: Re: [PATCH v4 4/8] rt2800: fix registers init for MT7620 To: Stanislaw Gruszka , Tom Psyborg Cc: linux-wireless@vger.kernel.org, Daniel Golle , Mathias Kresin References: <1539334591-9965-1-git-send-email-sgruszka@redhat.com> <1539334591-9965-5-git-send-email-sgruszka@redhat.com> <20181012113656.GB2118@redhat.com> <20181012120329.GD2118@redhat.com> <20181012122630.GB2668@redhat.com> <20181016080922.GB4158@redhat.com> From: Felix Fietkau Openpgp: preference=signencrypt Autocrypt: addr=nbd@nbd.name; prefer-encrypt=mutual; keydata= xsDiBEah5CcRBADIY7pu4LIv3jBlyQ/2u87iIZGe6f0f8pyB4UjzfJNXhJb8JylYYRzIOSxh ExKsdLCnJqsG1PY1mqTtoG8sONpwsHr2oJ4itjcGHfn5NJSUGTbtbbxLro13tHkGFCoCr4Z5 Pv+XRgiANSpYlIigiMbOkide6wbggQK32tC20QxUIwCg4k6dtV/4kwEeiOUfErq00TVqIiEE AKcUi4taOuh/PQWx/Ujjl/P1LfJXqLKRPa8PwD4j2yjoc9l+7LptSxJThL9KSu6gtXQjcoR2 vCK0OeYJhgO4kYMI78h1TSaxmtImEAnjFPYJYVsxrhay92jisYc7z5R/76AaELfF6RCjjGeP wdalulG+erWju710Bif7E1yjYVWeA/9Wd1lsOmx6uwwYgNqoFtcAunDaMKi9xVQW18FsUusM TdRvTZLBpoUAy+MajAL+R73TwLq3LnKpIcCwftyQXK5pEDKq57OhxJVv1Q8XkA9Dn1SBOjNB l25vJDFAT9ntp9THeDD2fv15yk4EKpWhu4H00/YX8KkhFsrtUs69+vZQwc0cRmVsaXggRmll dGthdSA8bmJkQG5iZC5uYW1lPsJgBBMRAgAgBQJGoeQnAhsjBgsJCAcDAgQVAggDBBYCAwEC HgECF4AACgkQ130UHQKnbvXsvgCgjsAIIOsY7xZ8VcSm7NABpi91yTMAniMMmH7FRenEAYMa VrwYTIThkTlQzsFNBEah5FQQCACMIep/hTzgPZ9HbCTKm9xN4bZX0JjrqjFem1Nxf3MBM5vN CYGBn8F4sGIzPmLhl4xFeq3k5irVg/YvxSDbQN6NJv8o+tP6zsMeWX2JjtV0P4aDIN1pK2/w VxcicArw0VYdv2ZCarccFBgH2a6GjswqlCqVM3gNIMI8ikzenKcso8YErGGiKYeMEZLwHaxE Y7mTPuOTrWL8uWWRL5mVjhZEVvDez6em/OYvzBwbkhImrryF29e3Po2cfY2n7EKjjr3/141K DHBBdgXlPNfDwROnA5ugjjEBjwkwBQqPpDA7AYPvpHh5vLbZnVGu5CwG7NAsrb2isRmjYoqk wu++3117AAMFB/9S0Sj7qFFQcD4laADVsabTpNNpaV4wAgVTRHKV/kC9luItzwDnUcsZUPdQ f3MueRJ3jIHU0UmRBG3uQftqbZJj3ikhnfvyLmkCNe+/hXhPu9sGvXyi2D4vszICvc1KL4RD aLSrOsROx22eZ26KqcW4ny7+va2FnvjsZgI8h4sDmaLzKczVRIiLITiMpLFEU/VoSv0m1F4B FtRgoiyjFzigWG0MsTdAN6FJzGh4mWWGIlE7o5JraNhnTd+yTUIPtw3ym6l8P+gbvfoZida0 TspgwBWLnXQvP5EDvlZnNaKa/3oBes6z0QdaSOwZCRA3QSLHBwtgUsrT6RxRSweLrcabwkkE GBECAAkFAkah5FQCGwwACgkQ130UHQKnbvW2GgCfTKx80VvCR/PvsUlrvdOLsIgeRGAAn1ee RjMaxwtSdaCKMw3j33ZbsWS4 Message-ID: Date: Tue, 16 Oct 2018 13:19:52 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181016080922.GB4158@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On 2018-10-16 10:09, Stanislaw Gruszka wrote: > On Fri, Oct 12, 2018 at 02:41:41PM +0200, Tom Psyborg wrote: >> On 12/10/2018, Stanislaw Gruszka wrote: >> > On Fri, Oct 12, 2018 at 02:20:07PM +0200, Tom Psyborg wrote: >> >> > On upstream tree where this patch is intended >> >> > additional registers where never programmed as proper branch >> >> > were never used, because of additional check in RT5390 branch. >> >> > >> >> >> >> on my hardware additional registers were programmed in regardless of >> >> redundant check. that why i opened whole thread on forum since i >> >> couldn't understand how's that happening >> > >> > I don't understand how that possible either. >> >> i'd assume because device use external lna > > I have no idea how this could be related. But I think I found > somewhat reasonable explenation where the problem is. > I think below code : > > if (a || b || c) { > CODE1(); > } else if (c) { > CODE2(); > } > > can not be deterministic and can be compiled differently depending > on compiler version and used options. Sometimes it could result > in this > > if (a || b || c) { > CODE1(); > } > > and sometimes in this: > > if (a || b) { > CODE1(); > } else if (c) { > CODE2(); > } > > So that would explain the problems you see. And indeed patch > could cause regression on systems where second variant of > initalizing RT6352 registers was used. I don't see how that can be non-deterministic at all. The 'else if' part can only be hit if the first if did not match. - Felix