From: Roger Quadros <rogerq@ti.com>
To: "DebBarma, Tarun Kanti" <tarun.kanti@ti.com>
Cc: "Varadarajan, Charulatha" <charu@ti.com>,
"linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>,
"Hilman, Kevin" <khilman@ti.com>,
"Shilimkar, Santosh" <santosh.shilimkar@ti.com>,
"tony@atomide.com" <tony@atomide.com>
Subject: Re: [PATCH v3 18/20] GPIO: OMAP: Use PM runtime framework
Date: Wed, 20 Jul 2011 12:33:14 +0300 [thread overview]
Message-ID: <4E26A0DA.5040202@ti.com> (raw)
In-Reply-To: <5A47E75E594F054BAF48C5E4FC4B92AB037C0C4D7B@dbde02.ent.ti.com>
On 07/20/2011 12:28 PM, DebBarma, Tarun Kanti wrote:
> [...]
>> From this patch it seems that the GPIO module is kept active as long as
>> one of its GPIOs is requested. This is not optimal.
> Yes, but...
>
>>
>> The GPIO needs to be active only when accessing its registers e.g.
>> during gpio_get or gpio_set. The rest of the time it can be suspended.
> A GPIO module would typically be used by multiple client drivers.
> However, the clock control is common for all GPIO pins within the module.
> So clocks can't be turned-off/on without negatively impacting present users.
Why not.
Let's say GPIO 1 and 2 belong to the same GPIO module.
Driver A uses GPIO 1 and driver B uses GPIO 2.
A is just blinking an LED every second whereas B uses GPIO 2 as input.
both drivers will keep the GPIOs requested as long as they are loaded.
Why can't you turn off the clocks when nobody is accessing GPIO registers?
In your current implementation, the GPIO module will never go idle.
cheers,
-roger
next prev parent reply other threads:[~2011-07-20 9:33 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-01 9:46 [PATCH v3 00/20] GPIO: OMAP: driver cleanup and fixes Tarun Kanti DebBarma
2011-07-01 9:46 ` [PATCH v3 01/20] GPIO: OMAP: Remove dependency on gpio_bank_count Tarun Kanti DebBarma
2011-07-01 9:46 ` [PATCH v3 02/20] GPIO: OMAP2+: Use flag to identify wakeup domain Tarun Kanti DebBarma
2011-07-01 9:46 ` [PATCH v3 03/20] GPIO: OMAP: Make gpio_context part of gpio_bank structure Tarun Kanti DebBarma
2011-07-01 9:46 ` [PATCH v3 04/20] GPIO: OMAP: Fix pwrdm_post_transition call sequence Tarun Kanti DebBarma
2011-07-01 9:46 ` [PATCH v3 05/20] GPIO: OMAP: Handle save/restore ctx in GPIO driver Tarun Kanti DebBarma
2011-07-01 9:47 ` [PATCH v3 06/20] GPIO: OMAP2+: Make non-wakeup GPIO part of pdata Tarun Kanti DebBarma
2011-07-01 9:47 ` [PATCH v3 07/20] GPIO: OMAP: Avoid cpu checks during module ena/disable Tarun Kanti DebBarma
2011-07-01 9:47 ` [PATCH v3 08/20] GPIO: OMAP: Use wkup regs off/suspend support flag Tarun Kanti DebBarma
2011-07-06 19:51 ` Kevin Hilman
2011-07-07 5:06 ` DebBarma, Tarun Kanti
2011-07-01 9:47 ` [PATCH v3 09/20] GPIO: OMAP: Use level/edge detect reg offsets Tarun Kanti DebBarma
2011-07-05 23:51 ` Kevin Hilman
2011-07-06 4:15 ` DebBarma, Tarun Kanti
2011-07-06 19:57 ` Kevin Hilman
2011-07-07 4:47 ` DebBarma, Tarun Kanti
2011-07-01 9:47 ` [PATCH v3 10/20] GPIO: OMAP: Remove hardcoded offsets in ctxt save/restore Tarun Kanti DebBarma
2011-07-01 9:47 ` [PATCH v3 11/20] GPIO: OMAP: Clean set_gpio_triggering function Tarun Kanti DebBarma
2011-07-01 9:47 ` [PATCH v3 12/20] GPIO: OMAP: Use wkup_status for all SoCs Tarun Kanti DebBarma
2011-07-06 0:50 ` Kevin Hilman
2011-07-06 4:30 ` DebBarma, Tarun Kanti
2011-07-06 4:33 ` DebBarma, Tarun Kanti
2011-07-12 0:04 ` DebBarma, Tarun Kanti
2011-07-12 15:30 ` Kevin Hilman
2011-07-13 3:55 ` DebBarma, Tarun Kanti
2011-07-01 9:47 ` [PATCH v3 13/20] GPIO: OMAP: Clean omap_gpio_mod_init function Tarun Kanti DebBarma
2011-07-06 20:38 ` Kevin Hilman
2011-07-07 4:40 ` DebBarma, Tarun Kanti
2011-07-01 9:47 ` [PATCH v3 14/20] GPIO: OMAP15xx: Use pinctrl offset instead of macro Tarun Kanti DebBarma
2011-07-01 9:47 ` [PATCH v3 15/20] GPIO: OMAP: Use readl in irq_handler for all access Tarun Kanti DebBarma
2011-07-01 9:47 ` [PATCH v3 16/20] GPIO: OMAP: Remove bank->method & METHOD_* macros Tarun Kanti DebBarma
2011-07-01 9:47 ` [PATCH v3 17/20] GPIO: OMAP: Fix bankwidth for OMAP7xx MPUIO Tarun Kanti DebBarma
2011-07-01 9:47 ` [PATCH v3 18/20] GPIO: OMAP: Use PM runtime framework Tarun Kanti DebBarma
2011-07-20 6:28 ` Roger Quadros
2011-07-20 9:28 ` DebBarma, Tarun Kanti
2011-07-20 9:33 ` Roger Quadros [this message]
2011-07-20 9:46 ` DebBarma, Tarun Kanti
2011-07-01 9:47 ` [PATCH v3 19/20] GPIO: OMAP: optimize suspend and resume functions Tarun Kanti DebBarma
2011-07-06 20:54 ` Kevin Hilman
2011-07-07 4:42 ` DebBarma, Tarun Kanti
2011-07-01 9:47 ` [PATCH v3 20/20] GPIO: OMAP2+: Clean prepare_for_idle and resume_after_idle Tarun Kanti DebBarma
2011-07-05 23:46 ` [PATCH v3 00/20] GPIO: OMAP: driver cleanup and fixes Kevin Hilman
2011-07-06 4:37 ` DebBarma, Tarun Kanti
2011-07-06 21:07 ` Kevin Hilman
2011-07-07 4:16 ` DebBarma, Tarun Kanti
2011-07-12 15:22 ` Hilman, Kevin
2011-07-13 3:48 ` DebBarma, Tarun Kanti
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