Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752637AbaBQJ5B (ORCPT ); Mon, 17 Feb 2014 04:57:01 -0500 Received: from perceval.ideasonboard.com ([95.142.166.194]:33066 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751660AbaBQJ47 (ORCPT ); Mon, 17 Feb 2014 04:56:59 -0500 From: Laurent Pinchart To: Magnus Damm Cc: Thomas Gleixner , Laurent Pinchart , SH-Linux , "linux-arm-kernel@lists.infradead.org" , linux-kernel , Daniel Lezcano Subject: Re: [PATCH 11/27] clocksource: sh_cmt: Add support for multiple channels per device Date: Mon, 17 Feb 2014 10:58:06 +0100 Message-ID: <3050110.8B4nKkQ5Sd@avalon> User-Agent: KMail/4.11.5 (Linux/3.10.25-gentoo; KDE/4.11.5; x86_64; ; ) In-Reply-To: References: <1392339605-20691-1-git-send-email-laurent.pinchart+renesas@ideasonboard.com> <2041255.QOGrHiKJmD@avalon> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Magnus, On Monday 17 February 2014 11:07:06 Magnus Damm wrote: > On Mon, Feb 17, 2014 at 10:48 AM, Laurent Pinchart wrote: > > On Monday 17 February 2014 10:41:31 Magnus Damm wrote: > >> On Mon, Feb 17, 2014 at 3:18 AM, Laurent Pinchart wrote: > >> > On Saturday 15 February 2014 13:46:54 Thomas Gleixner wrote: > >> >> On Fri, 14 Feb 2014, Laurent Pinchart wrote: > >> >> > CMT hardware devices can support multiple channels, with global > >> >> > registers and per-channel registers. The sh_cmt driver currently > >> >> > models the hardware with one Linux device per channel. This model > >> >> > makes it difficult to handle global registers in a clean way. > >> >> > > >> >> > Add support for a new model that uses one Linux device per timer > >> >> > with multiple channels per device. This requires changes to platform > >> >> > data, add new channel configuration fields. > >> >> > > >> >> > Support for the legacy model is kept and will be removed after all > >> >> > platforms switch to the new model. > >> >> > > >> >> > Signed-off-by: Laurent Pinchart > >> >> > > >> >> > --- > >> >> > > >> >> > drivers/clocksource/sh_cmt.c | 299 ++++++++++++++++++++++++-------- > >> >> > include/linux/sh_timer.h | 9 ++ > >> >> > 2 files changed, 239 insertions(+), 69 deletions(-) > >> >> > > >> >> > diff --git a/drivers/clocksource/sh_cmt.c > >> >> > b/drivers/clocksource/sh_cmt.c > >> >> > index 5280231..8390f0f 100644 > >> >> > --- a/drivers/clocksource/sh_cmt.c > >> >> > +++ b/drivers/clocksource/sh_cmt.c > > > > [snip] > > > >> >> > @@ -85,11 +94,15 @@ struct sh_cmt_info { > >> >> > > >> >> > struct sh_cmt_channel { > >> >> > struct sh_cmt_device *cmt; > >> >> > > >> >> > - unsigned int index; > >> >> > - void __iomem *base; > >> >> > + unsigned int index; /* Index in the documentation */ > >> >> > + unsigned int hwidx; /* Real hardware index */ > >> >> > + > >> >> > + void __iomem *iostart; > >> >> > + void __iomem *ioctrl; > >> >> > > >> >> > struct irqaction irqaction; > >> >> > >> >> While you are at it, can you please get rid of that irqaction and use > >> >> request_irq() ? > >> > > >> > The driver claims it can't use request_irq() because the function is > >> > not available for early platform devices. If the situation has changed > >> > I'd gladly get rid of irqaction. > >> > >> With the risk of stating the obvious, this depends on how early the > >> early platform device stuff is being run. The actual location may not > >> be the same on SH and ARM for instance. > >> > >> On ARM we are doing all we can to initialize these devices as late as > >> ever possible in the MULTIPLAFORM (DT reference) case. Once we manage > >> to remove the legacy ARM case then there is one less user of early > >> platform timers. > >> > >> One perhaps reasonable way forward could be to use request_irq() in > >> case of DT and leave the legacy platform data case to rely on > >> irqaction. > > > > The whole point of switching from setup_irq() to request_irq() is to > > simplify the code. Adding request_irq() as an option would go in the > > opposite direction. > > The point of switching to setup_irq() was not very clear to me. I > think it is fine to switch to using it over time, and I'm open to any > alternative ways forward. Usually moving in incremental steps means > more crap in the short term, but if someone could come up with a way > that involves little crap then I'm all for that! =) I've had a quick look at request_irq(). The function is defined as a static inline in include/linux/interrupt.h: static inline int __must_check request_irq(unsigned int irq, irq_handler_t handler, unsigned long flags, const char *name, void *dev) { return request_threaded_irq(irq, handler, NULL, flags, name, dev); } request_threaded_irq() is implemented in kernel/irq/manage.c. I've removed the code paths that would never be taken when called by the sh_cmt driver, due to - handler not being NULL - thread_fn being NULL - CONFIG_DEBUG_SHIRQ_FIXME not being set - IRQF_SHARED not being set int request_threaded_irq(unsigned int irq, irq_handler_t handler, irq_handler_t thread_fn, unsigned long irqflags, const char *devname, void *dev_id) { struct irqaction *action; struct irq_desc *desc; int retval; desc = irq_to_desc(irq); if (!desc) return -EINVAL; if (!irq_settings_can_request(desc) || WARN_ON(irq_settings_is_per_cpu_devid(desc))) return -EINVAL; action = kzalloc(sizeof(struct irqaction), GFP_KERNEL); if (!action) return -ENOMEM; action->handler = handler; action->thread_fn = thread_fn; action->flags = irqflags; action->name = devname; action->dev_id = dev_id; chip_bus_lock(desc); retval = __setup_irq(irq, desc, action); chip_bus_sync_unlock(desc); if (retval) kfree(action); return retval; } setup_irq() is implemented in the same file as int setup_irq(unsigned int irq, struct irqaction *act) { int retval; struct irq_desc *desc = irq_to_desc(irq); if (WARN_ON(irq_settings_is_per_cpu_devid(desc))) return -EINVAL; chip_bus_lock(desc); retval = __setup_irq(irq, desc, act); chip_bus_sync_unlock(desc); return retval; } The only two differences between request_irq() and setup_irq() would thus be - the extra !irq_settings_can_request(desc) check - the extra kzalloc() call The former should only be true for chained IRQ handlers, which isn't the case here. The latter is just a kmalloc + kmap_atomic + memset as far as I can tell. It thus seems safe to replace setup_irq() with request_irq(). -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/