From: Jon Hunter <jonathanh@nvidia.com>
To: "Dmitry Osipenko" <digetx@gmail.com>,
"Laxman Dewangan" <ldewangan@nvidia.com>,
"Vinod Koul" <vkoul@kernel.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Thierry Reding" <thierry.reding@gmail.com>,
"Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: <dmaengine@vger.kernel.org>, <linux-tegra@vger.kernel.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 11/16] dmaengine: tegra-apb: Keep clock enabled only during of DMA transfer
Date: Mon, 3 Feb 2020 11:37:44 +0000 [thread overview]
Message-ID: <423eb28f-b5fc-c917-a7b2-72562183683f@nvidia.com> (raw)
In-Reply-To: <bf459b54-fa4c-b0ff-0af8-b7cb66b0a43c@gmail.com>
On 01/02/2020 15:13, Dmitry Osipenko wrote:
> 31.01.2020 17:22, Dmitry Osipenko пишет:
>> 31.01.2020 12:02, Jon Hunter пишет:
>>>
>>> On 30/01/2020 20:04, Dmitry Osipenko wrote:
>>>
>>> ...
>>>
>>>>>> The tegra_dma_stop() should put RPM anyways, which is missed in yours
>>>>>> sample. Please see handle_continuous_head_request().
>>>>>
>>>>> Yes and that is deliberate. The cyclic transfers the transfers *should*
>>>>> not stop until terminate_all is called. The tegra_dma_stop in
>>>>> handle_continuous_head_request() is an error condition and so I am not
>>>>> sure it is actually necessary to call pm_runtime_put() here.
>>>>
>>>> But then tegra_dma_stop() shouldn't unset the "busy" mark.
>>>
>>> True.
>>>
>>>>>> I'm also finding the explicit get/put a bit easier to follow in the
>>>>>> code, don't you think so?
>>>>>
>>>>> I can see that, but I was thinking that in the case of cyclic transfers,
>>>>> it should only really be necessary to call the get/put at the beginning
>>>>> and end. So in my mind there should only be two exit points which are
>>>>> the ISR handler for SG and terminate_all for SG and cyclic.
>>>>
>>>> Alright, I'll update this patch.
>>>
>>> Hmmm ... I am wondering if we should not mess with that and leave how
>>> you have it.
>>
>> I took another look and seems my current v6 should be more correct because:
>>
>> 1. If "busy" is unset in tegra_dma_stop(), then the RPM should be put
>> there since tegra_dma_terminate_all() won't put RPM in this case:
>>
>> if (!tdc->busy)
>> goto skip_dma_stop;
>>
>> 2. We can't move the "busy" unsetting into the terminate because then
>> tegra_dma_stop() will be invoked twice. Although, one option could be to
>> remove the tegra_dma_stop() from the error paths of
>> handle_continuous_head_request(), but I'm not sure that this is correct
>> to do.
>
> Jon, I realized that my v6 variant is wrong too because
> tegra_dma_terminate_all() -> tdc->isr_handler() will put RPM, and thus,
> the RPM enable-count will be wrecked in this case.
Did you see my other suggestion to move the pm_runtime_put() outside of
tegra_dma_stop? There are only a few call sites for tegra_dma_stop and
so if we call pm_runtime_put() after calling tegra_dma_stop this should
simplify matters.
Jon
--
nvpublic
next prev parent reply other threads:[~2020-02-03 11:37 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-30 4:37 [PATCH v6 00/16] NVIDIA Tegra APB DMA driver fixes and improvements Dmitry Osipenko
2020-01-30 4:37 ` [PATCH v6 01/16] dmaengine: tegra-apb: Fix use-after-free Dmitry Osipenko
2020-01-30 4:37 ` [PATCH v6 02/16] dmaengine: tegra-apb: Prevent race conditions of tasklet vs free list Dmitry Osipenko
2020-01-30 4:37 ` [PATCH v6 03/16] dmaengine: tegra-apb: Implement synchronization hook Dmitry Osipenko
2020-01-30 4:37 ` [PATCH v6 04/16] dmaengine: tegra-apb: Prevent race conditions on channel's freeing Dmitry Osipenko
2020-01-30 4:37 ` [PATCH v6 05/16] dmaengine: tegra-apb: Clean up tasklet releasing Dmitry Osipenko
2020-01-30 4:37 ` [PATCH v6 06/16] dmaengine: tegra-apb: Use devm_platform_ioremap_resource Dmitry Osipenko
2020-01-30 4:37 ` [PATCH v6 07/16] dmaengine: tegra-apb: Use devm_request_irq Dmitry Osipenko
2020-01-30 4:37 ` [PATCH v6 08/16] dmaengine: tegra-apb: Fix coding style problems Dmitry Osipenko
2020-01-30 14:08 ` Jon Hunter
2020-01-30 4:37 ` [PATCH v6 09/16] dmaengine: tegra-apb: Remove unneeded initialization of tdc->config_init Dmitry Osipenko
2020-01-30 14:08 ` Jon Hunter
2020-01-30 4:37 ` [PATCH v6 10/16] dmaengine: tegra-apb: Remove assumptions about unavailable runtime PM Dmitry Osipenko
2020-01-30 14:09 ` Jon Hunter
2020-01-30 16:09 ` Dmitry Osipenko
2020-01-30 4:37 ` [PATCH v6 11/16] dmaengine: tegra-apb: Keep clock enabled only during of DMA transfer Dmitry Osipenko
2020-01-30 14:09 ` Jon Hunter
2020-01-30 16:11 ` Dmitry Osipenko
2020-01-30 18:45 ` Jon Hunter
2020-01-30 20:04 ` Dmitry Osipenko
2020-01-31 9:02 ` Jon Hunter
2020-01-31 14:22 ` Dmitry Osipenko
2020-02-01 15:13 ` Dmitry Osipenko
2020-02-03 11:37 ` Jon Hunter [this message]
2020-02-03 16:24 ` Dmitry Osipenko
2020-01-31 9:05 ` Jon Hunter
2020-01-30 4:38 ` [PATCH v6 12/16] dmaengine: tegra-apb: Clean up suspend-resume Dmitry Osipenko
2020-01-30 14:09 ` Jon Hunter
2020-01-30 16:08 ` Dmitry Osipenko
2020-01-30 18:06 ` Dmitry Osipenko
2020-01-30 18:26 ` Dmitry Osipenko
2020-01-30 18:58 ` Jon Hunter
2020-01-30 19:00 ` Jon Hunter
2020-01-30 20:06 ` Dmitry Osipenko
2020-01-30 4:38 ` [PATCH v6 13/16] dmaengine: tegra-apb: Add missing of_dma_controller_free Dmitry Osipenko
2020-01-30 4:38 ` [PATCH v6 14/16] dmaengine: tegra-apb: Allow to compile as a loadable kernel module Dmitry Osipenko
2020-01-30 4:38 ` [PATCH v6 15/16] dmaengine: tegra-apb: Remove MODULE_ALIAS Dmitry Osipenko
2020-01-30 4:38 ` [PATCH v6 16/16] dmaengine: tegra-apb: Support COMPILE_TEST Dmitry Osipenko
2020-01-30 14:10 ` Jon Hunter
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