From: Suman Anna <s-anna@ti.com>
To: Kishon Vijay Abraham I <kishon@ti.com>, Paul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>,
Bjorn Helgaas <bhelgaas@google.com>, <richardcochran@gmail.com>,
Russell King <linux@arm.linux.org.uk>,
<linux-omap@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <nsekhar@ti.com>
Subject: Re: [PATCH v3 3/3] pci: dra7xx: use pdata callbacks to perform reset
Date: Thu, 11 Feb 2016 14:43:02 -0600 [thread overview]
Message-ID: <56BCF256.8010903@ti.com> (raw)
In-Reply-To: <56BACCDB.2070507@ti.com>
On 02/09/2016 11:38 PM, Kishon Vijay Abraham I wrote:
> Hi,
>
> On Wednesday 10 February 2016 07:12 AM, Suman Anna wrote:
>> Hi Paul,
>>
>> On 02/09/2016 01:36 PM, Paul Walmsley wrote:
>>> Hi Suman
>>>
>>> On Tue, 9 Feb 2016, Suman Anna wrote:
>>>
>>>> On 02/09/2016 02:49 AM, Paul Walmsley wrote:
>>>>> On Mon, 8 Feb 2016, Suman Anna wrote:
>>>>>> On 02/07/2016 08:48 PM, Paul Walmsley wrote:
>>>>>>> On Tue, 2 Feb 2016, Kishon Vijay Abraham I wrote:
>>>>>>>
>>>>>>>> Paul, what do you think is the best way forward to perform reset?
>>>>>>>
>>>>>>> Many of the IP blocks with PRM hardreset lines are processor IP blocks.
>>>>>>> Those often need special reset handling to ensure that WFI/HLT-like
>>>>>>> instructions are executed after reset. This special handling ensures that
>>>>>>> the IP blocks' bus initiator interfaces indicate that they are in standby
>>>>>>> to the PRCM - thus allowing power management for the rest of the chip to
>>>>>>> work correctly.
>>>>>>>
>>>>>>> But that doesn't seem to be the case with PCIe - and maybe others -
>>>>>>> possibly some of the MMUs?
>>>>>>
>>>>>> Yeah, the sequencing between clocks and resets would still be the same
>>>>>> for MMUs, so, adding the custom flags for MMUs is fine.
>>>>>
>>>>> I'm curious as to whether HWMOD_CUSTOM_HARDRESET is needed for the MMUs.
>>>>> We've stated that the main point of the custom hardreset code is to handle
>>>>> processors that need to be placed into WFI/HLT, but it doesn't seem like
>>>>> there would be an equivalent for MMUs. Thoughts?
>>>>
>>>> The current OMAP IOMMU code already leverages the pdata ops for
>>>> performing the resets, so not adding the flags would also require
>>>> additional changes in the driver.
>>>>
>>>> Also, the reset lines controlling the MMUs actually also manage the
>>>> reset for all the other sub-modules other than the processor cores
>>>> within the sub-systems. We have currently different issues (see [1] for
>>>> eg. around the IPU sub-system entering RET in between), so from a PM
>>>> point of view, we do prefer to place the MMUs also in reset when we are
>>>> runtime suspended.
>>>
>>> Should we reassert hardreset in _idle() for IP blocks that don't have
>>> HWMOD_CUSTOM_HARDRESET set on them? Would that allow us to use this
>>> mechanism for the uncore hardreset lines, or are there other quirks?
>>>
>>> Also - would that address the potential issue that you mentioned with the
>>> PCIe block, or is that a different issue?
>>
>> Yeah, I think that would address the PCIe block issue in terms of reset
>> state balancing between pm_runtime_get_sync() and pm_runtime_put()
>> calls. Right now, they are unbalanced. The PCIe block is using these
>> only in probe and remove, so it should work for that IP.
>
> As I mentioned before this would result in undesired behavior during
> suspend/resume cycle in PCIe. (This should be okay for the current mainline
> code but would break once we add suspend/resume support for PCIe).
Yeah, I was wondering if some peripheral would want only the clock to be
controlled during _idle() and not reset. Even then for the PCIe case
that you are talking about, going through a pm_runtime_get_sync(),
pm_runtime_put_sync()/pm_runtime_put() deasserts the resets everytime
_enable() is called. Right now, the code block has ignored the return
value from the _hardreset_deassert(), but if you check it and bail out,
then your get_sync() would start failing from the second invocation.
Can you elaborate more on what kind of issues you will see on
suspend/resume cycle with PCIe? Do note that _idle() gets called through
_od_suspend_no_irq() in omap_device.c if your runtime status is not
suspended. I had to manage the runtime status in the IPU/DSP
suspend/resume code to deal with the reset
(omap_device_assert_hardreset) and clock sequences in
_idle()/omap_device_idle()
regards
Suman
next prev parent reply other threads:[~2016-02-11 20:43 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-14 14:11 [PATCH v3 0/3] dra7xx: get pcie working in mainline Kishon Vijay Abraham I
2016-01-14 14:11 ` [PATCH v3 1/3] ARM: DRA7: hwmod: Add reset data for PCIe Kishon Vijay Abraham I
2016-02-08 1:50 ` Paul Walmsley
2016-01-14 14:11 ` [PATCH v3 2/3] ARM: DRA7: add pdata-quirks to do reset of PCIe Kishon Vijay Abraham I
2016-01-15 19:19 ` Suman Anna
2016-01-15 19:22 ` Tony Lindgren
2016-01-15 19:41 ` Suman Anna
2016-01-18 9:12 ` Sekhar Nori
2016-01-27 17:23 ` Tony Lindgren
2016-01-14 14:11 ` [PATCH v3 3/3] pci: dra7xx: use pdata callbacks to perform reset Kishon Vijay Abraham I
2016-01-27 17:31 ` Tony Lindgren
2016-01-27 18:16 ` Suman Anna
2016-01-27 18:56 ` Tony Lindgren
2016-01-27 23:16 ` Suman Anna
2016-01-28 18:31 ` Tony Lindgren
2016-01-28 21:15 ` Suman Anna
2016-02-02 10:40 ` Kishon Vijay Abraham I
2016-02-05 4:19 ` Kishon Vijay Abraham I
2016-02-08 2:48 ` Paul Walmsley
2016-02-08 20:56 ` Suman Anna
2016-02-09 8:49 ` Paul Walmsley
2016-02-09 17:40 ` Suman Anna
2016-02-09 19:36 ` Paul Walmsley
2016-02-10 1:42 ` Suman Anna
2016-02-10 5:38 ` Kishon Vijay Abraham I
2016-02-11 19:27 ` Paul Walmsley
2016-02-11 22:04 ` Suman Anna
2016-02-12 6:49 ` Kishon Vijay Abraham I
2016-02-12 17:20 ` Suman Anna
2016-02-18 14:21 ` Sekhar Nori
2016-02-18 17:23 ` Paul Walmsley
2016-02-18 18:27 ` Suman Anna
2016-02-22 6:18 ` Kishon Vijay Abraham I
2016-02-22 6:31 ` Paul Walmsley
2016-02-22 9:55 ` Kishon Vijay Abraham I
2016-02-23 11:57 ` Kishon Vijay Abraham I
2016-02-23 18:28 ` Paul Walmsley
2016-02-24 6:21 ` Kishon Vijay Abraham I
2016-03-01 8:25 ` Paul Walmsley
2016-03-01 11:55 ` Kishon Vijay Abraham I
2016-03-01 14:43 ` Bjorn Helgaas
2016-03-01 16:55 ` Suman Anna
2016-02-11 20:43 ` Suman Anna [this message]
2016-02-12 6:55 ` Kishon Vijay Abraham I
2016-02-10 5:36 ` Kishon Vijay Abraham I
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