From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <1521385797.6569.90.camel@baylibre.com> Subject: Re: [PATCH 1/4] dt-bindings: clock: meson: update documentation with hhi syscon From: Jerome Brunet To: Rob Herring , Kevin Hilman , Neil Armstrong Cc: Carlo Caione , linux-amlogic@lists.infradead.org, linux-clk@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Date: Sun, 18 Mar 2018 16:09:57 +0100 In-Reply-To: <20180318125222.kqtybu4hiwvsx3om@rob-hp-laptop> References: <20180315115545.1884-1-jbrunet@baylibre.com> <20180315115545.1884-2-jbrunet@baylibre.com> <20180318125222.kqtybu4hiwvsx3om@rob-hp-laptop> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: On Sun, 2018-03-18 at 07:52 -0500, Rob Herring wrote: > On Thu, Mar 15, 2018 at 12:55:42PM +0100, Jerome Brunet wrote: > > The HHI register region hosts more than just clocks and needs to > > accessed drivers other than the clock controller, such as the display > > driver. > > > > This register region should be managed by syscon. It is already the case > > on gxbb/gxl and it soon will be on axg. The clock controllers must use > > this system controller instead of directly mapping the registers. > > Sounds like a kernel problem, not a DT one. It's a platform problem, so it has much a kernel problem (solution already merged) as a DT problem DT wise, we've got two devices mapping the same region in arch/arm64/boot/dts/amlogic/meson-gx.dtsi: > system-controller@0 which is used by the display device. and in arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi (same for gxl) > clock-controller@0 It has worked so far because the clock controller claims the region w/o reserving it but it remains unsafe since both device may access the same region. The fix is to have the clock controller go through the existing syscon. > > > > > With a single child, there is really no point to this change. A single > node can provide multiple functions. Look at nodes that are both reset > and clock providers. There is more than a single user, as explained above and in the cover letter of this series. > > What other functions are there? > > Rob