Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755104Ab2E3QNG (ORCPT ); Wed, 30 May 2012 12:13:06 -0400 Received: from bear.ext.ti.com ([192.94.94.41]:36543 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754325Ab2E3QNE (ORCPT ); Wed, 30 May 2012 12:13:04 -0400 Message-ID: <4FC646FF.1000209@ti.com> Date: Wed, 30 May 2012 11:12:47 -0500 From: Jon Hunter User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: "Cousson, Benoit" CC: Xiao Jiang , , , , , , , , , , , Subject: Re: [PATCH 3/3] watchdog: omap_wdt: add device tree support References: <1337942552-28218-1-git-send-email-jgq516@gmail.com> <1337942552-28218-4-git-send-email-jgq516@gmail.com> <4FC51008.1050004@ti.com> <4FC59171.8040009@gmail.com> <4FC5D21F.2030702@ti.com> <4FC636C9.2050902@ti.com> <4FC63D03.8080501@ti.com> In-Reply-To: <4FC63D03.8080501@ti.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [192.157.144.139] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4731 Lines: 124 Hi Benoit, On 05/30/2012 10:30 AM, Cousson, Benoit wrote: > Hi Jon, > > On 5/30/2012 5:03 PM, Jon Hunter wrote: >> Hi Benoit, >> >> On 05/30/2012 02:54 AM, Cousson, Benoit wrote: >>> On 5/30/2012 5:18 AM, Xiao Jiang wrote: >>>> Jon Hunter wrote: >>>>> On 05/25/2012 05:42 AM, jgq516@gmail.com wrote: >>>>>> From: Xiao Jiang >>>>>> >>>>>> Add device table for omap_wdt to support dt. >>>>>> >>>>>> Signed-off-by: Xiao Jiang >>>>>> --- >>>>>> drivers/watchdog/omap_wdt.c | 8 ++++++++ >>>>>> 1 files changed, 8 insertions(+), 0 deletions(-) >>>>>> >>>>>> diff --git a/drivers/watchdog/omap_wdt.c >>>>>> b/drivers/watchdog/omap_wdt.c >>>>>> index 8285d65..d98c615 100644 >>>>>> --- a/drivers/watchdog/omap_wdt.c >>>>>> +++ b/drivers/watchdog/omap_wdt.c >>>>>> @@ -430,6 +430,13 @@ static int omap_wdt_resume(struct >>>>>> platform_device *pdev) >>>>>> #define omap_wdt_resume NULL >>>>>> #endif >>>>>> >>>>>> +static const struct of_device_id omap_wdt_of_match[] = { >>>>>> + { .compatible = "ti,omap3-wdt", }, >>>>>> + { .compatible = "ti,omap4-wdt", }, >>> >>> If there is no difference between the OMAP3 and the OMAP4 WDT IP, just >>> add one entry "ti,omap3-wdt". And then in the OMAP4 DTS you will just >>> put : compatible = "ti,omap3-wdt"; or compatible = "ti,omap4-wdt", >>> "ti,omap3-wdt"; >> >> Hmmm ... comparing the omap3 and omap4 wdt registers there are some >> differences. omap4 seems to have more registers than omap3. May be we >> are not using these right now, but from a register perspective the wdt >> in omap2, omap3 and omap4 appear to be slightly different. The revision >> ID register on omap3 and omap4 have different values too. >> >> I guess from a driver perspective there is no difference, but it seemed >> to me that the IP is not completely the same. > > Well, in that case, and assuming that there is no proper HW_REVISION > information to detect the IP difference, the proper compatible entries > will indeed have to be used. So looking at a 4460 and 3430, the WIDR register (IP revision) can be used to distinguish between IP revisions. So it appears that we do have proper HW REV info. So may be I am not completely up to speed of the intent of the compatible field. In other words, should this be used to indicate if the IP is same/compatible or the driver is compatible or both. Technically right now we could just have "ti-omap2-wdt" for all omap2+ devices as the driver is compatible for all devices. However, technically, the IP is not completely the same but it is compatible :-) >>> I'm still a little bit confused about the real need for the >>> "ti,omap4-wdt: entry, but it seems to be the way to do it in PPC. >>> >>>>>> + {}, >>>>>> +}; >>>>>> +MODULE_DEVICE_TABLE(of, omap_wdt_of_match); >>>>>> + >>>>>> static struct platform_driver omap_wdt_driver = { >>>>>> .probe = omap_wdt_probe, >>>>>> .remove = __devexit_p(omap_wdt_remove), >>>>>> @@ -439,6 +446,7 @@ static struct platform_driver omap_wdt_driver = { >>>>>> .driver = { >>>>>> .owner = THIS_MODULE, >>>>>> .name = "omap_wdt", >>>>>> + .of_match_table = omap_wdt_of_match, >>>>>> }, >>>>>> }; >>>>>> >>>>> >>>>> I think we need to add some code to the probe function that calls >>>>> of_match_device() and ensures we find a match. For example ... >>>>> >>>>> if (of_have_populated_dt()) >>>>> if (!of_match_device(omap_wdt_of_match,&pdev->dev)) >>>>> return -EINVAL; >>>>> >>>> Will add it in v2, thanks for suggestion. >>> >>> No, in fact this is not needed. We need that mainly when several >>> instances can match the same driver and thus we select the proper one >>> using the of_match_device. Otherwise, just check is the device_node is >>> there. >>> >>> In that case, the driver does not even care about any DT node so there >>> is no need to add extra code for that. Keep it simple. >> >> Ok. So are you saying get rid of the match table altogether? In other >> words, drop this patch? > > No, the match table is used by the LDM to find the proper driver to be > bound to a device. So we do need it. But we do not have to use the > of_match_device if we do not want to get the entry in the device table. Ok, thanks. >> I agree that it does not really do anything today, but I did not know if >> in the future you were planning to pass things like, register addresses, >> via DT. > > Well, yes we will have to, otherwise people will keep complaining that > our DTS sucks and are not compliant with the DTS standards :-) Ok. Jon -- 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/