linux-kernel - Re: [PATCH v9 01/25] gpio/omap: remove dependency on gpio_bank

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 2 Feb 2012 21:48:13 +0100
From:	"Cousson, Benoit" <b-cousson@...com>
To:	<balbi@...com>, <khilman@...com>
CC:	Grant Likely <grant.likely@...retlab.ca>,
	Tarun Kanti DebBarma <tarun.kanti@...com>,
	<linux-omap@...r.kernel.org>, <tony@...mide.com>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, Charulatha V <charu@...com>
Subject: Re: [PATCH v9 01/25] gpio/omap: remove dependency on gpio_bank_count

On 2/2/2012 8:45 PM, Felipe Balbi wrote:
> On Thu, Feb 02, 2012 at 12:16:30PM -0700, Grant Likely wrote:
>> On Thu, Feb 02, 2012 at 08:41:07PM +0200, Felipe Balbi wrote:
>>> Hi,
>>>
>>> On Thu, Feb 02, 2012 at 11:00:27PM +0530, Tarun Kanti DebBarma wrote:
>>>> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
>>>> index 0b05629..6ea7390 100644
>>>> --- a/drivers/gpio/gpio-omap.c
>>>> +++ b/drivers/gpio/gpio-omap.c
>>>> @@ -28,7 +28,10 @@
>>>>   #include<asm/gpio.h>
>>>>   #include<asm/mach/irq.h>
>>>>
>>>> +static LIST_HEAD(omap_gpio_list);
>>>
>>> I guess it's now too late because patch is acked and everything, but I
>>> think if you make the driver handle one bank alone and just instantiate
>>> it multiple times (omap_gpio.0, omap_gpio.1, omap_gpio.3, etc) driver
>>> would be faaaaaar simpler.
>>
>> Is there any shared state between the banks?  On my very cursory glance it
>> looked like banks still have some interaction between them.  If not, then
>> yes I agree that multiple instances would be better.
>
> A quick glance at the TRM shows that banks have separate address spaces
> and IRQ lines. I think it's done this way because we can handoff one (or
> more) bank to other cores on the SoC, so they need to be pretty
> independent.
>
> I could be missing something though.

In fact the driver already handled the 6 GPIOS banks as individual devices:

[    0.185638] gpiochip_add: registered GPIOs 0 to 31 on device: gpio
[    0.185882] OMAP GPIO hardware version 0.1
[    0.186767] gpiochip_add: registered GPIOs 32 to 63 on device: gpio
[    0.187744] gpiochip_add: registered GPIOs 64 to 95 on device: gpio
[    0.188751] gpiochip_add: registered GPIOs 96 to 127 on device: gpio
[    0.189819] gpiochip_add: registered GPIOs 128 to 159 on device: gpio
[    0.190917] gpiochip_add: registered GPIOs 160 to 191 on device: gpio

That list is only used to iterate over all the instances during CPU idle:

void omap2_gpio_prepare_for_idle(int pwr_mode)
{
	struct gpio_bank *bank;

	list_for_each_entry(bank, &omap_gpio_list, node) {
		if (!bank->mod_usage || !bank->loses_context)
			continue;

		bank->power_mode = pwr_mode;

		pm_runtime_put_sync_suspend(bank->dev);
	}
}

void omap2_gpio_resume_after_idle(void)
{
	struct gpio_bank *bank;

	list_for_each_entry(bank, &omap_gpio_list, node) {
		if (!bank->mod_usage || !bank->loses_context)
			continue;

		pm_runtime_get_sync(bank->dev);
	}
}


I don't know if there is some reason to not use driver_for_each_device.


Kevin,

Do we have any constraint inside omap_sram_idle to not use the device 
iterator?


Regards,
Benoit
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/