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Tue, 30 Apr 2019 20:15:50 +0000 (GMT) Subject: Re: [PATCH v6 06/10] dt-bindings: memory-controllers: add Exynos5422 DMC device description To: Rob Herring Cc: devicetree@vger.kernel.org, "linux-kernel@vger.kernel.org" , "open list:THERMAL" , linux-samsung-soc , Bartlomiej Zolnierkiewicz , Krzysztof Kozlowski , Kukjin Kim , Chanwoo Choi , Kyungmin Park , Marek Szyprowski , Sylwester Nawrocki , MyungJoo Ham , Kees Cook , Tony Lindgren , Joerg Roedel , Thierry Reding , Dmitry Osipenko , willy.mh.wolff.ml@gmail.com From: Lukasz Luba Message-ID: <8f488d35-d576-a710-c24b-18514c6c0f34@partner.samsung.com> Date: Tue, 30 Apr 2019 22:15:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA02SbUhTYRTHe3Zfdh1tPE7LU1nRKjIhtRfpCcUKQi5FkdKHSiFveTPJme2q ZfVhKVhaZqhYLc38kqKWabJ8Q2NZrqzcyF5QhpFmpa4SX0CKrOtd5Lf/Oed3+P8PHI7S/2AW c4nJqaIpWUgysBra+nS6e910jT02xGZdSuqu1zLk3cRnhpR1vGJI9dgAIoXPS1XkxSUjyR8Y oUh39301eZk5qiavm0tYMp7Xgcj17jYVudvhUpO+85UsmWltVJPHoxcY0t6zk/T91JEp+0e0 zYefmiyg+ZtmJ803WVxqvr4qh+Xzsr6x/JWGKsQ/6DrLj9cv28sd1ITHi0mJ6aIpOCJOc+xG MUl55H/anuNGZtTil4u8OMCboCfLinKRhtPjSgS9nx+olGICgWu4hVaKcQSZ71z0v5WsyXuM MqhAUNd031O4EVRkO5FM+eCjYBmyqmTti1fAz+ziWYjCkwxk1xT9hTiOxUHQWHVSZrQ4Er5c qZzlabwaSm6OsrJegPdD/1PZQGa84dmNwdkUXjgKpsztallT2A96B8tUil4OD90llOwFuJSD tnK7Wom9A2rtTo/2geHOBo/2h5kmZRmwBOa8cqToczCQX+phwuBxp5ORM1N4LdQ2Byvt7fDV UcTKbcA6eO/2ViLooMB6jVLaWriYrVfoAGi47PAYLYSKmmL1VWSwzDnMMucYy5xjLP99byO6 CvmJaZIxQZQ2JIungiTBKKUlJwQdOWGsR3//sOt350Qjav512IYwhwzztY5Ie6yeEdKlDKMN AUcZfLV855NYvTZeyDgjmk4cMqUliZINLeFog5/27LwPMXqcIKSKx0UxRTT9m6o4r8VmdMsS MhLRFZ1+VBU9mn/c5c4prB9aeOdtdcS+soL0SaFgviUmbPequJz96Bwuar23xFEe3q/bMhQP a55vDo1xeEcZ4sMHxoSuUiOrmgkLaf5kYtyZe968WKRzD9UsGtwY+nv3LscBm3lqemXA1qge aOAr66KcPdYPmu+htYFjOwy0dExYH0iZJOEPxxW6MoMDAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFmphleLIzCtJLcpLzFFi42I5/e/4Xd3va07EGDz5K2mxccZ6VovrX56z Wsw/co7VYvXHx4wWk0/NZbI4051r0f/4NbPF+fMb2C3ONr1ht7i8aw6bxefeI4wWM87vY7JY e+Quu8XtxhVsFv/37GC3OPymndVi/xUvi9u/+Sy+nXjE6CDs8e3rJBaP2Q0XWTx2zrrL7rFp VSebR2/zOzaPvi2rGD02n672+LxJLoAjSs+mKL+0JFUhI7+4xFYp2tDCSM/Q0kLPyMRSz9DY PNbKyFRJ384mJTUnsyy1SN8uQS9j5jSLggMyFSc63zI2MO4W72Lk5JAQMJFo/rqOtYuRi0NI YCmjxNeTJ9ggEmISk/ZtZ4ewhSX+XOtigyh6zShx8tViJpCEsECaxOWrz1hAbBEBRYnfbdPA JjEL/GSVOHOoiRGio4VZYteXDiCHg4NNQE9ix6pCkAZeATeJF30rwAaxCKhKzJn9BmyzqECE xJn3K1ggagQlTs58AmZzCgRKfGvYD3YRs4CZxLzND5khbHGJW0/mM0HY8hLb385hnsAoNAtJ +ywkLbOQtMxC0rKAkWUVo0hqaXFuem6xkV5xYm5xaV66XnJ+7iZGYArYduznlh2MXe+CDzEK cDAq8fBqeJ6IEWJNLCuuzD3EKMHBrCTC63H8aIwQb0piZVVqUX58UWlOavEhRlOg5yYyS4km 5wPTU15JvKGpobmFpaG5sbmxmYWSOG+HwMEYIYH0xJLU7NTUgtQimD4mDk6pBsa9BrWFh1uV uqy/KrBdnfq9WeXTrMyklcKzF4jvuXXmMiPH+nK7ZLMj+987NMux663v+VD371X0VM3goLiU 6bn2rrc1bj3Wupcxe7n3Bnlf3bdnFk9Yl+fRFZPfz3/6xu9rWvHFQf/muJVlZc32rvn07OIO VcPCzebTWLhPMr+QFOU+Y8WvI6zEUpyRaKjFXFScCADu9m08FwMAAA== X-CMS-MailID: 20190430201552eucas1p20e6654bf0e5f922312977bd8180e9be0 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20190419141947eucas1p13a27605e04169ab528ef5bfb385eddbc X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20190419141947eucas1p13a27605e04169ab528ef5bfb385eddbc References: <1555683568-20882-1-git-send-email-l.luba@partner.samsung.com> <1555683568-20882-7-git-send-email-l.luba@partner.samsung.com> <20190425195750.GA26031@bogus> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/29/19 6:43 PM, Rob Herring wrote: > On Mon, Apr 29, 2019 at 7:14 AM Lukasz Luba wrote: >> >> Hi Rob, >> >> On 4/25/19 9:57 PM, Rob Herring wrote: >>> On Fri, Apr 19, 2019 at 04:19:24PM +0200, Lukasz Luba wrote: >>>> The patch adds description for DT binding for a new Exynos5422 Dynamic >>>> Memory Controller device. >>>> >>>> Signed-off-by: Lukasz Luba >>>> --- >>>> .../bindings/memory-controllers/exynos5422-dmc.txt | 73 ++++++++++++++++++++++ >>>> 1 file changed, 73 insertions(+) >>>> create mode 100644 Documentation/devicetree/bindings/memory-controllers/exynos5422-dmc.txt >>>> >>>> diff --git a/Documentation/devicetree/bindings/memory-controllers/exynos5422-dmc.txt b/Documentation/devicetree/bindings/memory-controllers/exynos5422-dmc.txt >>>> new file mode 100644 >>>> index 0000000..133b3cc >>>> --- /dev/null >>>> +++ b/Documentation/devicetree/bindings/memory-controllers/exynos5422-dmc.txt >>>> @@ -0,0 +1,73 @@ >>>> +* Exynos5422 frequency and voltage scaling for Dynamic Memory Controller device >>>> + >>>> +The Samsung Exynos5422 SoC has DMC (Dynamic Memory Controller) to which the DRAM >>>> +memory chips are connected. The driver is to monitor the controller in runtime >>>> +and switch frequency and voltage. To monitor the usage of the controller in >>>> +runtime, the driver uses the PPMU (Platform Performance Monitoring Unit), which >>>> +is able to measure the current load of the memory. >>>> +When 'userspace' governor is used for the driver, an application is able to >>>> +switch the DMC and memory frequency. >>>> + >>>> +Required properties for DMC device for Exynos5422: >>>> +- compatible: Should be "samsung,exynos5422-bus". >>>> +- clock-names : the name of clock used by the bus, "bus". >>>> +- clocks : phandles for clock specified in "clock-names" property. >>>> +- devfreq-events : phandles for PPMU devices connected to this DMC. >>>> +- vdd-supply : phandle for voltage regulator which is connected. >>>> +- reg : registers of two CDREX controllers, chip information, clocks subsystem. >>>> +- operating-points-v2 : phandle for OPPs described in v2 definition. >>>> +- device-handle : phandle of the connected DRAM memory device. For more >>>> + information please refer to Documentation >>> >>> The memory node(s) should be a child of the memory controller IMO. >> I have followed the TI code for LPDDR2. They use 'device-handle' >> probably because the memory controller can be moved into the common >> .dtsi and taken by reference in .dts in a proper board file. > > You'd still have to have the ctrlr node in the board file to add the > 'device-handle' property. > >> The board .dts files might specify different DRAM chips and timings. >> In Exynos case we will also have such situation: one memory controller >> and a few different DRAM chips. > > You mean as in the case where there are multiple options and one chip > gets populated on the board? So 'device-handle' is selecting which > chip to use. Yes. The 'device-handle' will point to different memories depending on the board/SoCs. There are boards with Exynos 5420, 5422, 5800 which are 'almost' the same, but with different memories glued on top (the PoP LPDDR3). > > You can actually do both here. Keep 'device-handle' to select which > DRAM chip and have the chips as child nodes. But if you really don't > want to have them as child nodes, that's fine. For now, I would like to keep it like this (if Krzysztof also agrees with the implementation). Regards, Lukasz > > Rob > >