From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kunihiko Hayashi Date: Mon, 05 Feb 2018 12:03:35 +0000 Subject: Re: [PATCH] fbdev: simplefb: add support for 'memory-region' property on DT node Message-Id: <20180205210334.32F0.4A936039@socionext.com> List-Id: References: <2359956.Z9lQWSAgHb@amdc3058> <20180205060914.4wherneafj6dfnev@rob-hp-laptop> In-Reply-To: <20180205060914.4wherneafj6dfnev@rob-hp-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Rob Herring Cc: Bartlomiej Zolnierkiewicz , Hans de Goede , linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Mark Rutland , devicetree@vger.kernel.org Hi Rob, On Mon, 5 Feb 2018 00:09:14 -0600 wrote: > On Thu, Feb 01, 2018 at 04:56:08PM +0100, Bartlomiej Zolnierkiewicz wrote: > > > > Hi, > > > > On Tuesday, January 23, 2018 08:34:56 PM Kunihiko Hayashi wrote: > > > Enables 'memory-region' property referring to the memory description on > > > the reserved-memory node in case of devicetree use. > > > If there is no 'reg' property that specifies the address and size of > > > the framebuffer, the address and size written in the memory description > > > on the reserved-memory node can be used for the framebuffer. > > > > > > Furthermore, the reserved-memory node needs to have "no-map" attributes > > > because simplefb driver maps the region by ioremap_wc(). > > > > > > Signed-off-by: Kunihiko Hayashi > > > > This needs an ACK from Rob or Mark (DT bindings Maintainers). > > > > > --- > > > .../bindings/display/simple-framebuffer.txt | 3 ++ > > > drivers/video/fbdev/simplefb.c | 32 ++++++++++++++++++++++ > > > 2 files changed, 35 insertions(+) > > > > > > diff --git a/Documentation/devicetree/bindings/display/simple-framebuffer.txt b/Documentation/devicetree/bindings/display/simple-framebuffer.txt > > > index 5a9ce51..be5139f 100644 > > > --- a/Documentation/devicetree/bindings/display/simple-framebuffer.txt > > > +++ b/Documentation/devicetree/bindings/display/simple-framebuffer.txt > > > @@ -56,6 +56,9 @@ Optional properties: > > > framebuffer remains active. > > > > > > - display : phandle pointing to the primary display hardware node > > > +- memory-region: phandle to a node describing memory region as framebuffer > > > + memory instead of reg property. The node should include > > > + 'no-map'. > > This should also state when it's appropriate to use this instead of reg. > The memory would only be reclaimed if reg is used. > > Though I'm wondering what keeps the simple fb memory from getting used > by the OS if reserved memory is not always used. Sorry that my understanding might not be correct. Since a framebuffer defined by "reserved-memory" can't be reclaimed, I've assumed such the framebuffer was dedicated and had some restrictions by device or firmware. Even in that case, You mean that we describe only "reg" directly, not go through "reserved-memory". Is that correct? It might be better to define new driver handling the dedicated framebuffer rather than using simple-fb, though, I'm not sure. --- Best Regards, Kunihiko Hayashi