From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Date: Sun, 01 Feb 2015 09:36:54 +0000 Subject: Re: [PATCH v4 5/5] drivers: bus: Add Simple Power-Managed Bus Driver Message-Id: List-Id: References: <1422288977-20353-1-git-send-email-geert+renesas@glider.be> <1422288977-20353-6-git-send-email-geert+renesas@glider.be> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org Hi Ulf, On Fri, Jan 30, 2015 at 10:34 AM, Ulf Hansson wrote: > On 26 January 2015 at 17:16, Geert Uytterhoeven wrote: >> Add a driver for transparent busses that don't need a real driver, but >> where the bus controller is part of a PM domain, or under the control of >> a functional clock. Typically, the bus controller's PM domain and/or >> clock must be enabled for child devices connected to the bus (either >> on-SoC or externally) to function. >> >> Hence the sole purpose of this driver is to enable its clock and PM >> domain (if exist(s)), which are specified in the DT and managed from >> platform and PM domain code, and to probe for child devices. >> >> Due to the child-parent relationship with devices connected to the bus, >> PM domain and clock state transitions are handled in the correct order. >> >> Signed-off-by: Geert Uytterhoeven >> Tested-by: Ulrich Hecht >> --- /dev/null >> +++ b/drivers/bus/simple-pm-bus.c >> +static int simple_pm_bus_probe(struct platform_device *pdev) >> +{ >> + struct device_node *np = pdev->dev.of_node; >> + >> + dev_dbg(&pdev->dev, "%s\n", __func__); >> + >> + pm_runtime_enable(&pdev->dev); >> + >> + if (np) >> + of_platform_populate(np, NULL, NULL, &pdev->dev); >> + > > I am not sure my comments is valid in this initial step. Yet, you > state in the DT documentation, that this driver supports clocks and PM > domains. > > How you are going add that support it quite interesting. :-) I also The clock can be controlled through e.g. pm_clk domain (pm_clk_notifier and pm_clk_{suspend,resume}()) or genpd (GENPD_FLAG_PM_CLK, which you have added yourself ;-) > especially interested how the interaction (child to parents) through > runtime PM will look like. When a child is to be runtime-resumed, the core make sure the parent is runtime-resumed. When all children have been runtime-suspended, the parent is runtime-suspended. This is already working. This patch series is the only missing piece: without a driver that calls pm_runtime_enable(), the parent is not runtime-managed. > Overall, I like the idea in patchset, but I would like to understand a > bit more around the above. Thanks! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds