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 65D40173; Tue, 5 Aug 2025 18:05:33 +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=1754417133; cv=none; b=TPfIeESUevcVDVM0bspl/5DP3HsTkqcOSE7DZzey14vvYx7hlmRd4E25agnvsLZzmr5SqdoGQKboQ/TRjQ/O002H7L0AJ+9bzpC+fu9HAmYJQMSWOWt8uDGYzI0QVPTtD7zhR5oVgPbiWHYFs70/r3to26WYskm8DkgswzoAkW8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754417133; c=relaxed/simple; bh=I8l4aEPhunyIiXsphJiO2yvHDN3RGwpiOWAw7vGoz/w=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nqN9umCU6a9Vk5fYr2DtpLQtazCDij0AELNNuGWuNP+XkfAQxAqsfXtt66Ef4LOvBLS0f9X3CDwXIvRVZZxwWI2gs5Q+rRqB4FPmntVS1YRLAzKw2r2cAzUc5VR3oxL193CtDmi2+6gkNrtJ5PjEiEvAVDnyD9Rvr/VTUu522pc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=op3YUS62; 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="op3YUS62" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0A6FC4CEF0; Tue, 5 Aug 2025 18:05:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754417133; bh=I8l4aEPhunyIiXsphJiO2yvHDN3RGwpiOWAw7vGoz/w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=op3YUS6265cXhd+My1YsGad9AV27PDz+VTP8/WsrMWqFxSudtHzhe1ymMLrPBCBik +qkk7L+idjGN7g/YtAAu2ijGybT+7CTujSy+PtoM5kMbFYqq4gUzh3GrfeDhSQond0 K3uOg46ik/Timi7wcdKGG6qMgHA+P0/Bpi1owj9NMV6Kw7nduenteMgGaZPFxTF7kk azUJmbA15/O1c7WLaJiFLF5m6l6HmW/O5h3SrBX03joISlYjbbG3aa9uNVVuTljcys qdnhEseGcyZCndLSLU28g9St7H5qtpMqy6aMsdRq0kTn2N+YmnKUYAirkv7/3IKYWZ bAT7xnCh8yhqA== Date: Tue, 5 Aug 2025 11:05:31 -0700 From: Drew Fustini To: Yao Zi Cc: Rob Herring , Guo Ren , Fu Wei , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Krzysztof Kozlowski , Conor Dooley , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Emil Renner Berthing , Jisheng Zhang , linux-riscv@lists.infradead.org, netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net v2 2/3] net: stmmac: thead: Get and enable APB clock on initialization Message-ID: References: <20250801091240.46114-1-ziyao@disroot.org> <20250801091240.46114-3-ziyao@disroot.org> <20250803170206.GA525144-robh@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Aug 04, 2025 at 09:23:00AM -0700, Drew Fustini wrote: > On Mon, Aug 04, 2025 at 05:12:26AM +0000, Yao Zi wrote: > > On Sun, Aug 03, 2025 at 12:02:06PM -0500, Rob Herring wrote: > > > On Fri, Aug 01, 2025 at 09:12:39AM +0000, Yao Zi wrote: > > > > It's necessary to adjust the MAC TX clock when the linkspeed changes, > > > > but it's noted such adjustment always fails on TH1520 SoC, and reading > > > > back from APB glue registers that control clock generation results in > > > > garbage, causing broken link. > > > > > > > > With some testing, it's found a clock must be ungated for access to APB > > > > glue registers. Without any consumer, the clock is automatically > > > > disabled during late kernel startup. Let's get and enable it if it's > > > > described in devicetree. > > > > > > > > Fixes: 33a1a01e3afa ("net: stmmac: Add glue layer for T-HEAD TH1520 SoC") > > > > Signed-off-by: Yao Zi > > > > Reviewed-by: Drew Fustini > > > > Tested-by: Drew Fustini > > > > --- > > > > drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c | 6 ++++++ > > > > 1 file changed, 6 insertions(+) > > > > > > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c > > > > index c72ee759aae5..95096244a846 100644 > > > > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c > > > > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c > > > > @@ -211,6 +211,7 @@ static int thead_dwmac_probe(struct platform_device *pdev) > > > > struct stmmac_resources stmmac_res; > > > > struct plat_stmmacenet_data *plat; > > > > struct thead_dwmac *dwmac; > > > > + struct clk *apb_clk; > > > > void __iomem *apb; > > > > int ret; > > > > > > > > @@ -224,6 +225,11 @@ static int thead_dwmac_probe(struct platform_device *pdev) > > > > return dev_err_probe(&pdev->dev, PTR_ERR(plat), > > > > "dt configuration failed\n"); > > > > > > > > + apb_clk = devm_clk_get_optional_enabled(&pdev->dev, "apb"); > > > > > > The description sounds like this should not be optional. The binding > > > change also makes it not optional. > > > > Yes, it shouldn't be. But using the non-optional API will cause the > > driver fails to probe with the old (problematic) devicetree, IOW, it > > breaks the ABI. Comparing to unusable ethernet, failing to adjust the > > link speed sounds a minor point to me. > > I've just read Conor's comment in the v1 again: > > Nah, introduce the warnings. If the clock is required for operation, it > should be marked as such. You've made it optional in the driver, which > is the important part (backwards compatible) and you've got the dts > patch in the series. > > Thus I think the argument I made in my reply to this thread is > incorrect and the driver should remain backwards compatible. > > > Maybe we could add a comment to explain why optional API is used, or > > just use the non-optional one if such ABI breakages are acceptable -- > > for which I'd like to wait for more opinions. > > I think a comment in the code about why it uses the optional variant of > the function is a good idea. I was chatting on devicetree irc channel, and I think that it would be good to add something like this to the commit message: For the purposes of backwards compatibility, the probe will not fail if 'apb' is not found, but the link will break if the speed changes after probe. Also, if devm_clk_get_optional_enabled("apb") fails, then I think it would be a good idea to warn the user that changing the link speed will not be supported. Thanks, Drew