From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7B3ED381D8 for ; Tue, 17 Oct 2023 09:29:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="BtdxdiAv"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="81B32lN2" Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D0D7FD55; Tue, 17 Oct 2023 02:29:12 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1697534951; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=9sKaZ+DU3SskjI6E8phB+glqoGJwjS+nS0gFA9gAqr0=; b=BtdxdiAvKf4xp0/qbT65QMMI2KZEBljih08tmtJCeLHT2Ir+wD0e/aBib4HUQl3QVuPFBz f7NgYJLJc3uda4x+7dJ8Kal5raQGKcXb+DYZCsh3KRyU20hmDRrUSDML+Mx+nQkkzPgW/K lN41GGXks+DewycAi7aArKC9unL0pDJ+/8LO9/L6Sf2vhf86TEnSd7cpAcnOAuSjVrddA0 RNXSbJoAf0NFF3rlqgC4Ay2npMek7YUHfN4CuqwUzSFnjjNZvJKaViInZDy3M7AizKGdMP 910qkR3zawLCneLf2K4Ot4S1bTEouraumZA4ULiEgaF/WfTU2+LJR4jkLAXJjw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1697534951; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=9sKaZ+DU3SskjI6E8phB+glqoGJwjS+nS0gFA9gAqr0=; b=81B32lN2+7b3Kg0VOfHVncb3RVfhbE1McS81o2QK6HZUGE9xq4HSHV8BOPkvsAOSrtieGw gto1/hAGhDTiLICg== To: lakshmi.sowjanya.d@intel.com, jstultz@google.com, giometti@enneenne.com, corbet@lwn.net, linux-kernel@vger.kernel.org Cc: x86@kernel.org, linux-doc@vger.kernel.org, andriy.shevchenko@linux.intel.com, eddie.dong@intel.com, christopher.s.hall@intel.com, pandith.n@intel.com, mallikarjunappa.sangannavar@intel.com, thejesh.reddy.t.r@intel.com, lakshmi.sowjanya.d@intel.com Subject: Re: [PATCH v1 2/6] x86/tsc: Convert Time Stamp Counter (TSC) value to Always Running Timer (ART) In-Reply-To: <20231017052457.25287-3-lakshmi.sowjanya.d@intel.com> References: <20231017052457.25287-1-lakshmi.sowjanya.d@intel.com> <20231017052457.25287-3-lakshmi.sowjanya.d@intel.com> Date: Tue, 17 Oct 2023 11:29:10 +0200 Message-ID: <87wmvl61i1.ffs@tglx> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_BLOCKED, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Tue, Oct 17 2023 at 10:54, lakshmi.sowjanya.d@intel.com wrote: > > +/* > + * Converts input TSC to the corresponding ART value using conversion > + * factors discovered by detect_art(). > + * > + * Return: 0 on success, -errno on failure. bool indicating success / fail ? > + */ > +int convert_tsc_to_art(const struct system_counterval_t *system_counter, > + u64 *art) > +{ > + u64 tmp, res, rem; > + /* ART = TSC * tsc_to_art_denominator / tsc_to_art_numerator */ > + struct u32_fract tsc_to_art = { > + .numerator = art_to_tsc_denominator, > + .denominator = art_to_tsc_numerator, > + }; The purpose of this struct is to obfuscate the code, right? The struct would make sense if a pointer would be handed to some other function. > + if (system_counter->cs != art_related_clocksource) > + return -EINVAL; > + > + res = system_counter->cycles - art_to_tsc_offset; > + rem = do_div(res, tsc_to_art.denominator); > + > + tmp = rem * tsc_to_art.numerator; > + do_div(tmp, tsc_to_art.denominator); > + *art = res * tsc_to_art.numerator + tmp; Yet another copy of the math in convert_art_to_tsc() and in convert_art_ns_to_tsc(). Seriously? Can we please have _one_ helper function which takes value, nominator, denominator as arguments and clean up the copy&pasta instead of adding more? Thanks, tglx