From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from verein.lst.de (verein.lst.de [213.95.11.211])
	(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 E0D711F754C
	for <linux-kernel@vger.kernel.org>; Fri, 17 Jan 2025 09:58:37 +0000 (UTC)
Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211
ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116;
	t=1737107919; cv=none; b=FEGN/mAIafIQmdnTXrkrHkAQYH7mgn6kfKpbvMs1769Xcwg2Ax1XJoSZn3k7gI991xPFj30lFmMsOn41PlmC28v3IrKohu3KBlbnNEMDqwpUaIywnYYIi7cOFeKzjtMe2qGCF2iP0DP6PlYSUpgPm1FhpFTFv/+KC2LbdooFtGo=
ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org;
	s=arc-20240116; t=1737107919; c=relaxed/simple;
	bh=R8OqgHqN0EsjFn9k3QbiZsQLiwNYRFK74e3l9A+1NE4=;
	h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version:
	 Content-Type:Content-Disposition:In-Reply-To; b=IMjJLA8kNSqzWd+8L+fhIjnsmOhEs8Tdy4pA6Lw+476KFj+UXWwVjjkMR1L4CpBp/av/kJTH4HO4xwFH/WIo2ZbRurug3XwnuCafboNGh9WooITXtP7GPvxqZOl+HFXXE8GRrhpN7Yd/bYwUNNRIHLWB8OCRiLkJ3fzkdH3Goi8=
ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211
Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de
Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de
Received: by verein.lst.de (Postfix, from userid 2407)
	id 81DB168BEB; Fri, 17 Jan 2025 10:58:32 +0100 (CET)
Date: Fri, 17 Jan 2025 10:58:32 +0100
From: Christoph Hellwig <hch@lst.de>
To: Sergey Matyukevich <geomatsi@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>, linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org, Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexandre Ghiti <alexghiti@rivosinc.com>,
	Conor Dooley <conor.dooley@microchip.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	Geert Uytterhoeven <geert+renesas@glider.be>
Subject: Re: [PATCH] riscv: select DMA_DIRECT_REMAP by RISCV_ISA_SVPBMT and
 ERRATA_THEAD_MAE
Message-ID: <20250117095832.GB2585@lst.de>
References: <20250116172950.1989748-1-geomatsi@gmail.com> <20250117075238.GA25422@lst.de> <Z4oXF2ewizIIk1cL@curiosity>
Precedence: bulk
X-Mailing-List: linux-kernel@vger.kernel.org
List-Id: <linux-kernel.vger.kernel.org>
List-Subscribe: <mailto:linux-kernel+subscribe@vger.kernel.org>
List-Unsubscribe: <mailto:linux-kernel+unsubscribe@vger.kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Z4oXF2ewizIIk1cL@curiosity>
User-Agent: Mutt/1.5.17 (2007-11-01)

On Fri, Jan 17, 2025 at 11:38:47AM +0300, Sergey Matyukevich wrote:
> > Please explain what this is supposed to solve, because the above
> > explanation dosn't make any sense.  DMA_DIRECT_REMAP is one
> > of the implementations supporting dma coherent allocatiosn for
> > non-coherent devices.  So selecting it from something that
> > just keyes off support for an extension, but not the dma
> > implementation is wrong.
> 
> Now DMA_DIRECT_REMAP is selected either by Zicbom (standard) or XTheadCmo
> (vendor) RISC-V extensions.

Because they need DMA_DIRECT_REMAP to implement DMA coherent.

> However neither of them can help to implement
> DMA_DIRECT_REMAP on RISC-V. So selection of DMA_DIRECT_REMAP has been
> moved in Kconfigs to Svpbmt and XTheadMae extensions.

But Svpbmt does not imply that you even need DMA_DIRECT_REMAP.

Are you tying to solve a problem here?  If so can you explain it?