From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CB5487C0A4; Sat, 17 Feb 2024 16:27:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708187256; cv=none; b=jnLp4roxueIUY/LPZ/5DqP9noP4WkpYcDj9EZxMXjEkajGw0OU+Igd/L4QjQRdAJ4PUR42LrurHDFQjwRwPQx3E2ePFehGnLX2jKAVwO5O3wsmjkDxy7Or2CTwsg1tNZ66THSgASVNXmuuZITPBeZYp5PdmQLJElxeMGH5l4GTo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708187256; c=relaxed/simple; bh=OxQUJIbmzj1GSzutcw5Ae7+lxbWZuacLVGzXpfA7VVw=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=KJmlGGPOLB2XxYZ+xUiDL+hrCt0bzaoLvTi7n4ScnAIpgLoM7ZtiNE0jKJUcAdB+AjA7XyT6GT4P9Uvqt0xcRlcj2GofdnyCOBdjArh2RnyPpnjoKSYdG8bCDNZ3ys1/jxPLBR/6Xc2Mc/i7dKdPLF0vZ4hgzbaFiHtFUUQjui4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PgvXsaS1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PgvXsaS1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DBD62C433C7; Sat, 17 Feb 2024 16:27:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1708187256; bh=OxQUJIbmzj1GSzutcw5Ae7+lxbWZuacLVGzXpfA7VVw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=PgvXsaS1v8qai/8BwB0Dz7/3XyllpWX4krFIKs2Ct4c0wQnk0i751CtaXMqP7+BBA DZXpfae8uBz2e9IL+CowZt3L9WuAJmd02uR0/+ge83Lb/TIwaXRM9wy8vXCDVjVp2f Qp7VuW+vyAgg1tUTR584QRjvX8In1UEuzP0nfhjO+YUZpFEF0ftwnWah9ceaNPnZ2s k1SblMCTJ3zwyjxlACWeC35Zl/92A/BU4wsnTK2h6cliFVIfGoRgTqnr7QOmJZ2Ngr VZbqBoaaNjWQxgr05bINKWXJSeeCCOCVF8c69xeYCoDPAVxsDANrh/ehDboG0Pphx2 /K6rXv5azRBLQ== Date: Sat, 17 Feb 2024 16:27:24 +0000 From: Jonathan Cameron To: Subhajit Ghosh Cc: Matti Vaittinen , Matti Vaittinen , Lars-Peter Clausen , linux-kernel@vger.kernel.org, David Laight , linux-iio@vger.kernel.org Subject: Re: [RESEND PATCH v2] iio: gts-helper: Fix division loop Message-ID: <20240217162724.767f2ab6@jic23-huawei> In-Reply-To: References: <20240216135812.07c9b769@jic23-huawei> X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sun, 18 Feb 2024 01:09:33 +1030 Subhajit Ghosh wrote: > On 17/2/24 00:28, Jonathan Cameron wrote: > > On Mon, 12 Feb 2024 13:20:09 +0200 > > Matti Vaittinen wrote: > > > >> The loop based 64bit division may run for a long time when dividend is a > >> lot bigger than the divider. Replace the division loop by the > >> div64_u64() which implementation may be significantly faster. > >> > >> Signed-off-by: Matti Vaittinen > >> Fixes: 38416c28e168 ("iio: light: Add gain-time-scale helpers") > >> > >> --- > >> This is a resend. Only change is the base which is now the v6.8-rc4 and > >> not the v6.8-rc1 > > Given I'm not rushing this in, it is going via my togreg tree, so the > > rebase wasn't really helpful (thankfully didn't stop it applying). > > Would have been fine to send a ping response to the first posting of it. > > > > I was leaving some time for David or Subhajit to have time to take > > another look, but guess they are either happy with this or busy. > > > > Applied to the togreg branch of iio.git and pushed out as testing for > > all the normal reasons. > > > > Jonathan > > > >> > >> This change was earlier applied and reverted as it confusingly lacked of > >> the removal of the overflow check (which is only needed when we do > >> looping "while (full > scale * (u64)tmp)". As this loop got removed, the > >> check got also obsolete and leaving it to the code caused some > >> confusion. > >> > >> So, I marked this as a v2, where v1 is the reverted change discussed > >> here: > >> https://lore.kernel.org/linux-iio/ZZZ7pJBGkTdFFqiY@dc78bmyyyyyyyyyyyyydt-3.rev.dnainternet.fi/ > >> > >> Revision history: > >> v1 => v2: > >> - Drop the obsolete overflow check > >> - Rebased on top of the v6.8-rc4 > >> > >> iio: gts: loop fix fix > >> --- > >> drivers/iio/industrialio-gts-helper.c | 15 +-------------- > >> 1 file changed, 1 insertion(+), 14 deletions(-) > >> > >> diff --git a/drivers/iio/industrialio-gts-helper.c b/drivers/iio/industrialio-gts-helper.c > >> index 7653261d2dc2..b51eb6cb766f 100644 > >> --- a/drivers/iio/industrialio-gts-helper.c > >> +++ b/drivers/iio/industrialio-gts-helper.c > >> @@ -34,24 +34,11 @@ > >> static int iio_gts_get_gain(const u64 max, const u64 scale) > >> { > >> u64 full = max; > >> - int tmp = 1; > >> > >> if (scale > full || !scale) > >> return -EINVAL; > >> > >> - if (U64_MAX - full < scale) { > >> - /* Risk of overflow */ > >> - if (full - scale < scale) > >> - return 1; > >> - > >> - full -= scale; > >> - tmp++; > >> - } > >> - > >> - while (full > scale * (u64)tmp) > >> - tmp++; > >> - > >> - return tmp; > >> + return div64_u64(full, scale); > >> } > >> > >> /** > Hi Matti and Jonathan, > > I somehow missed testing this patch earlier. The above patch works fine with apds9306 v7 driver(which work in progress!). > There are no errors. > My test script is simple: > #!/bin/bash > D=0 > S=`cat /sys/bus/iio/devices/iio:device${D}/in_illuminance_scale_available` > > for s in $S; do > echo $s > echo $s > /sys/bus/iio/devices/iio:device${D}/in_illuminance_scale > sleep 5 > done > > One question - if I test a patch like this, do I put a "Tested-by" tag or just mention that I have tested it? Both are useful - so thanks for this email. Preference for a formal tag though as that goes in the git commit and we have a convenient record that both says you tested it + that we should make sure to cc you on related changes as you may well be in a position to test those as well! Thanks, Jonathan > > Regards, > Subhajit Ghosh > > >> > >> base-commit: 841c35169323cd833294798e58b9bf63fa4fa1de > > >