From: nsekhar@ti•com (Sekhar Nori)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v5 1/6] pwms: pwm-ti*: Get the clock from the PWMSS (parent)
Date: Tue, 12 Apr 2016 13:40:44 +0530 [thread overview]
Message-ID: <570CAD84.2090701@ti.com> (raw)
In-Reply-To: <CAL_JsqLkpQzVb6bzpsH5NwfLLWEtf3o6LezrL1hCejsw65J=Bw@mail.gmail.com>
On Monday 11 April 2016 06:15 PM, Rob Herring wrote:
> On Mon, Apr 11, 2016 at 6:49 AM, Sekhar Nori <nsekhar@ti•com> wrote:
>> On Monday 11 April 2016 02:21 AM, Paul Walmsley wrote:
>>> On Tue, 5 Apr 2016, Franklin S Cooper Jr. wrote:
>>>> On 04/05/2016 01:08 AM, Sekhar Nori wrote:
>>>>> On Tuesday 08 March 2016 06:53 AM, Franklin S Cooper Jr wrote:
>>>>>> The eCAP and ePWM doesn't have their own separate clocks. They simply
>>>>>> utilize the clock provided directly by the PWMSS. Therefore, they simply
>>>>>> need to grab a reference to their parent's clock.
>>>>>>
>>>>>> Signed-off-by: Franklin S Cooper Jr <fcooper@ti•com>
>>>>>
>>>>> So this assumes that eCAP and eHRPWM are always under the PWMSS
>>>>> umbrella. But on TI AM18x, thats not true. These IPs exist independently
>>>>> and receive functional clock from PLL sysclk outputs.
>>>>>
>>>>>> ---
>>>>>> drivers/pwm/pwm-tiecap.c | 2 +-
>>>>>> drivers/pwm/pwm-tiehrpwm.c | 2 +-
>>>>>> 2 files changed, 2 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/pwm/pwm-tiecap.c b/drivers/pwm/pwm-tiecap.c
>>>>>> index 616af76..9418159 100644
>>>>>> --- a/drivers/pwm/pwm-tiecap.c
>>>>>> +++ b/drivers/pwm/pwm-tiecap.c
>>>>>> @@ -212,7 +212,7 @@ static int ecap_pwm_probe(struct platform_device *pdev)
>>>>>> if (!pc)
>>>>>> return -ENOMEM;
>>>>>>
>>>>>> - clk = devm_clk_get(&pdev->dev, "fck");
>>>>>> + clk = devm_clk_get(pdev->dev.parent, "fck");
>>>>>
>>>>> Even keeping the AM18x usecase aside, this seems to be pushing too much
>>>>> platform information into the driver. The "fck" is a valid connection id
>>>>> for the eCAP IP. Whether its valid for the parent device too is not
>>>>> something this driver should need to know.
>>>>>
>>>>> So it looks like what you need is for the clock hierarchy for the
>>>>> platform to have clocks for eHRPWM and eCAP derived out of PWMSS clock?
>>>>
>>>> So I believe this is a question on if we want to hide the minor
>>>> delta between AM18 vs AM335x, AM437x and AM57x/DRA7 in the driver
>>>> or within the DT.
>>>>
>>>> Note that handling this by defining new clocks in DT will then
>>>> result in older DTBs not working. I don't think its worth breaking
>>>> backwards compatibility for AM335x and AM437x DTBs for fixing support
>>>> for AM18 based SOCs. Especially since those SOCs haven't worked with
>>>> this driver for several years. By handling things within the driver rather
>>>> than DT we can atleast insure that we can get everything working while
>>>> avoiding breaking backwards compatibility.
>>>
>>> I agree with Sekhar that we shouldn't embed this parent clock quirk
>>> into the driver.
>>>
>>> Can you just define a new compatibility string such that the driver can be
>>> written with no embedded integration quirks? Then add a workaround in the
>>> driver that will use pdev->dev.parent for the old (deprecated)
>>> compatibility string and log a warning to the kernel console that the DT
>>> needs to be updated.
>>
>> Thanks Paul! Although not sure if adding a new compatible for the IP is
>> the best way (since that would denote a different version of the IP).
>> How about checking for parent clock iff clk_get() on own device fails
>> and of_machine_is_compatible() matches the platforms where backward
>> compatibility needs to be maintained?
>
> New compatible strings are acceptable.
Alright, thanks for clarifying that.
Regards,
Sekhar
next prev parent reply other threads:[~2016-04-12 8:10 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-08 1:23 [PATCH v5 0/6] ARM: am335x/am437x/dra7: Add PWM support for DRA7 Franklin S Cooper Jr
2016-03-08 1:23 ` [PATCH v5 1/6] pwms: pwm-ti*: Get the clock from the PWMSS (parent) Franklin S Cooper Jr
2016-03-17 22:37 ` Franklin S Cooper Jr.
2016-04-05 6:08 ` Sekhar Nori
2016-04-05 11:25 ` Franklin S Cooper Jr.
2016-04-10 20:51 ` Paul Walmsley
2016-04-11 11:49 ` Sekhar Nori
2016-04-11 12:45 ` Rob Herring
2016-04-12 8:10 ` Sekhar Nori [this message]
2016-03-08 1:23 ` [PATCH v5 2/6] ARM: dts: am437x/am33xx: Remove eCAP and ePWM hwmod properties Franklin S Cooper Jr
2016-03-08 1:23 ` [PATCH v5 3/6] ARM: AM335x/AM437x: hwmod: Remove eQEP, ePWM and eCAP hwmod entries Franklin S Cooper Jr
2016-03-17 15:06 ` Rob Herring
2016-03-17 15:45 ` Franklin S Cooper Jr.
2016-03-17 19:04 ` Rob Herring
2016-03-08 1:23 ` [PATCH v5 4/6] ARM: OMAP2+: DRA7: Add hwmod entries for PWMSS Franklin S Cooper Jr
2016-03-08 6:45 ` Paul Walmsley
2016-04-10 18:57 ` Paul Walmsley
2016-03-08 1:23 ` [PATCH v5 5/6] ARM: dts: DRA7: Add TBCLK " Franklin S Cooper Jr
2016-04-11 20:21 ` Tony Lindgren
2016-04-11 20:27 ` Tony Lindgren
2016-03-08 1:23 ` [PATCH v5 6/6] ARM: dts: DRA7: Add dt nodes " Franklin S Cooper Jr
2016-03-17 15:11 ` Rob Herring
2016-03-17 15:53 ` Franklin S Cooper Jr.
2016-04-11 20:21 ` Tony Lindgren
2016-04-19 16:20 ` Franklin S Cooper Jr.
2016-03-08 6:55 ` [PATCH v5 0/6] ARM: am335x/am437x/dra7: Add PWM support for DRA7 Paul Walmsley
2016-03-08 17:04 ` Franklin S Cooper Jr.
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=570CAD84.2090701@ti.com \
--to=nsekhar@ti$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox