From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris BREZILLON Subject: Re: [PATCH v2 1/7] mfd: add atmel-hlcdc driver Date: Sun, 15 Jun 2014 16:48:58 +0200 Message-ID: <539DB25A.4000201@free-electrons.com> References: <1402329860-27520-1-git-send-email-boris.brezillon@free-electrons.com> <1402329860-27520-2-git-send-email-boris.brezillon@free-electrons.com> <539D5F24.1020304@traphandler.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <539D5F24.1020304@traphandler.com> Sender: linux-kernel-owner@vger.kernel.org To: jjhiblot@traphandler.com, Thierry Reding , Nicolas Ferre , David Airlie , Samuel Ortiz , Lee Jones Cc: Alexandre Belloni , Jean-Christophe Plagniol-Villard , Laurent Pinchart , devicetree@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, dri-devel@lists.freedesktop.org List-Id: devicetree@vger.kernel.org Hello JJ, On 15/06/2014 10:53, Jean-Jacques Hiblot wrote: > On 06/09/2014 06:04 PM, Boris BREZILLON wrote: >> The HLCDC IP available on some Atmel SoCs (i.e. at91sam9n12, at91sam9x5 >> family or sama5d3 family) exposes 2 subdevices: >> - a display controller (controlled by a DRM driver) >> - a PWM chip >> >> Add support for the MFD device which will just retrieve HLCDC clocks and >> create a regmap so that subdevices can access the HLCDC register range >> concurrently. >> >> Signed-off-by: Boris BREZILLON >> --- >> .../devicetree/bindings/mfd/atmel-hlcdc.txt | 41 ++++++++ >> drivers/mfd/Kconfig | 11 ++ >> drivers/mfd/Makefile | 1 + [...] >> + memset(&config, 0, sizeof(config)); >> + config.reg_bits = 32; >> + config.val_bits = 32; >> + config.reg_stride = 4; >> + config.max_register = (resource_size(res) / 4) - 1; >> + hlcdc->regmap = devm_regmap_init_mmio_clk(dev, "periph_clk", regs, >> + &config); > I don't think it's necessary to use "periph_clk" here. This clock will > always be running because the HLCDC needs it to work (it's not just an > interface clock). In the end it's just some extra work for each register > access. Yes, I thought about removing this clk from regmap registration too (for the exact same reason: avoiding extra enable/disable work when accessing registers), but ATM I do not prepare/enable periph_clk in the hlcdc-pwm driver, this means the regmap won't work until the hlcdc-dc driver has probed the display controller device. How about preparing/enabling the periph_clk in the MFD device, so that PWM and Display Controller subdevices won't have to bother about this clk, and the regmap will work as expected ? Or, should we just prepare/enable the periph clock in each subdevices ? Best Regards, Boris -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com