From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f54.google.com (mail-wm1-f54.google.com [209.85.128.54]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 67C351F463A; Fri, 13 Jun 2025 15:56:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.54 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749830204; cv=none; b=s7dNHHfALcB3fjZFo21Z+snAfxnH67wzp76pggtSIeW6b1VdA+//9+h3lqbawCtHsY7Tt+IEEY4fRbty/qUeSRb6ceBtdDq5o1P5DcwpsU162OLAlITNbnKwVmrKUgGSANwx4UTsxlpbPJJrMeDqpP6Qds6xRoSyIxtN6Kb7aFM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749830204; c=relaxed/simple; bh=OwWwJMJMz1gVCx/M2Des8/aF3uScnadX1L2LxSc73zo=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=lia9isCdDn+IcmhDXLd2Q8vDRPSTI5AXPs4EZgDLbgPuPCZmBc+U41vrVvEqoPkdRbW/hKVcuiyBIkBcgVot/CkH7BeuPse1QyWWeXYqNBHAS8GPZnGI8H+1tvE0RTMl0aAT8DNWQaWgEigtIu+g9DagAb8GSOV9hLwnNOYdVvY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=WtJvzLIU; arc=none smtp.client-ip=209.85.128.54 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WtJvzLIU" Received: by mail-wm1-f54.google.com with SMTP id 5b1f17b1804b1-43edecbfb46so17596385e9.0; Fri, 13 Jun 2025 08:56:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1749830201; x=1750435001; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=qPo6H/9j3Ay9teefhcqMxpNsx0jvAC7MjlPzeeLu5rE=; b=WtJvzLIU5z2gsfsyfs2NvE2Vu7stYrE5zg/WHTCxjLyuQODy45mMFrGEmc7kWcWLTy 4R9qZwdcJRuvjWLR/fVHIbY5KrMRoiqiMBIbub671TSbcQBrFEsBM3pFNVy1LhsSFhFF 1iJIgn/+b4Nxzl+F7tns8XM85R1tZSosw8Cntr1hUSk9rk2bhDX6d7y9r+plULrNpqO6 WYIw/g/mSb9hCylllFa1ts6WPeyrUfRtoLWKtSRH3foSDLQAhGMa6hE52LMejbtbcBHo PJpgXUbJA0Lc7339r+XDHop8zPLqKsRVuPa+6aAO63MLhbYekKM+3PfNfosQG8IZqZic J15A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1749830201; x=1750435001; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qPo6H/9j3Ay9teefhcqMxpNsx0jvAC7MjlPzeeLu5rE=; b=jxybNoFOl3guTZDbva2/WThvZ54R6rfFHM2DwSyD2S4bQWrvGYOvXCVziyBZi5ZvnM 6c6zwmDsfu8dUIr6tUoQnYEwp8Pya/XKaLReTYgz+LnQhWXzhMo1+ocOUPub+M3laYID iSQZ96xIq88DNdwIFDlPa8lc8DgvWZLcIzxIgLzP7kjBTpWWJW2scS/9tbc87KAY8ZtE t2m4IZzIW5Nfl3zIYn8wIf8xMGtnwtZkx6Y0u7HYCozfUWrh3RzHK2llgrYaEtmNDEXQ +JEe3+w4p23tajN03r3KGBedXtjIYBrCowpFk7rNtr77a94SMBMq6JPc1RhGsHAoSqWI u/Kg== X-Forwarded-Encrypted: i=1; AJvYcCWSEP5+zTleaWixrzwhYIf67HvXNynMOP1RT/1CkRKn+0jvbOPAM0tz0ZHqgX9zvOS2gC0mymwhKx9U@vger.kernel.org, AJvYcCWgGN6WcqZ6ETswc4EwGJpKE1Rb2M08EJAu2MQwaaciCXE2KbB453ZbfAeaux6CAYV+YwhXLyV/FBmTN8s=@vger.kernel.org X-Gm-Message-State: AOJu0YxxY9j/2CJotS7zs3tPLmEQJ0tSIwOlVrm5LqPxSdcXAbxgRP/Y xPIN5sIxH72QFEHwRiCaK97L4llA+q2ZEWiosXIp1+ep2s/c0r/0U5d3IlVRiQ== X-Gm-Gg: ASbGnctbGWTI9LCzcVYddYEmZCxRUaVx9e1WXk+Dmv+nWOJbGXeH7eaQAYOU3No+iV7 5+ab4dv9oATYRny7wtmQdtvdWApyOJWzNjtcHakYfosD3QtwzOTqIac44Gno6/yZTo2qCMkW4Dm VndF+WOw/OsUBjqTK61Lw/Pqki4IybvaQYULPD1dOgFOVE1XISO1jtL3mzddUuTg6BaPNumJyIU imP3lWXsJ2WJ7ieeUUL/U2SoP26qXsnk+MP4V179mvHmiYbs+UFaCh39Fhr+5gvKownTGr9N813 6jLKLweAX26/ixmWTOShYv75Rza/BsnscwEybubodkjqpFEbbOqd4i8VolHsbe9aNDg/+F8PyLh /j++dBxWYsfSuBqOabKkOM8P/ X-Google-Smtp-Source: AGHT+IEek+xBG8qH6etYMJhHA/6eRULw+qWjFJ15S/9q/UV/dFart736CLdrph6JJHU+y3p0PfPeMA== X-Received: by 2002:a05:6000:4284:b0:3a4:da87:3a73 with SMTP id ffacd0b85a97d-3a572e8cd82mr226657f8f.42.1749830200407; Fri, 13 Jun 2025 08:56:40 -0700 (PDT) Received: from pumpkin (82-69-66-36.dsl.in-addr.zen.co.uk. [82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a568a54b7asm2782895f8f.16.2025.06.13.08.56.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Jun 2025 08:56:40 -0700 (PDT) Date: Fri, 13 Jun 2025 16:56:38 +0100 From: David Laight To: James Clark Cc: Frank Li , Vladimir Oltean , Mark Brown , Vladimir Oltean , linux-spi@vger.kernel.org, imx@lists.linux.dev, linux-kernel@vger.kernel.org, Arnd Bergmann Subject: Re: [PATCH 2/4] spi: spi-fsl-dspi: Use non-coherent memory for DMA Message-ID: <20250613165638.5d8ed000@pumpkin> In-Reply-To: References: <20250609-james-nxp-spi-dma-v1-0-2b831e714be2@linaro.org> <20250609-james-nxp-spi-dma-v1-2-2b831e714be2@linaro.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@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 Tue, 10 Jun 2025 16:46:36 +0100 James Clark wrote: > On 10/06/2025 4:15 pm, Frank Li wrote: > > On Mon, Jun 09, 2025 at 04:32:39PM +0100, James Clark wrote: > >> Using coherent memory here isn't functionally necessary. > >> Because the > >> change to use non-coherent memory isn't overly complex and only a few > >> synchronization points are required, we might as well do it while fixing > >> up some other DMA issues. > > > > Any beanfit by use on-coherent memory here? > > > > Frank > > > > Presumably less cache maintenance traffic? I bet it only helps when cache-coherent memory has to be uncached. Otherwise the software cache operations are pretty much guaranteed to be more expensive than the hardware ones. David