linux-kernel - Re: Regression in Linux next with dma cma changes

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Date:   Tue, 26 Feb 2019 12:15:19 -0800
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sebastian Reichel <sre@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-omap@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: Regression in Linux next with dma cma changes

On Tue, Feb 26, 2019 at 12:01:55PM -0800, Tony Lindgren wrote:
> Looks like commit d222e42e8816 ("dma-contiguous: do not allocate a
> single page from CMA area") caused a regression at least for
> omap dss where we now get the following error on init:
> 
> omapdss_dispc 58001000.dispc:
> dispc_errata_i734_wa_init: dma_alloc_writecombine failed
> 
> Any ideas what might be going wrong?

It's probably because the dma_alloc_from_contiguous() call in
this path doesn't rebound to allocate a normal single page.

And I guess we should have left the change within dma-direct.

Christoph, do you agree?

I am submitting a revert first.