From: Dmitry Osipenko <digetx@gmail.com>
To: "Jon Hunter" <jonathanh@nvidia.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: Thu, 30 Jan 2020 19:11:54 +0300 [thread overview]
Message-ID: <0c766352-700a-68bf-cf7b-9b1686ba9ca9@gmail.com> (raw)
In-Reply-To: <2442aee7-2c2a-bacc-7be9-8eed17498928@nvidia.com>
30.01.2020 17:09, Jon Hunter пишет:
>
> On 30/01/2020 04:37, Dmitry Osipenko wrote:
>> It's a bit impractical to enable hardware's clock at the time of DMA
>> channel's allocation because most of DMA client drivers allocate DMA
>> channel at the time of the driver's probing, and thus, DMA clock is kept
>> always-enabled in practice, defeating the whole purpose of runtime PM.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>> drivers/dma/tegra20-apb-dma.c | 47 ++++++++++++++++++++++++-----------
>> 1 file changed, 32 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
>> index 22b88ccff05d..0ee28d8e3c96 100644
>> --- a/drivers/dma/tegra20-apb-dma.c
>> +++ b/drivers/dma/tegra20-apb-dma.c
>> @@ -436,6 +436,8 @@ static void tegra_dma_stop(struct tegra_dma_channel *tdc)
>> tdc_write(tdc, TEGRA_APBDMA_CHAN_STATUS, status);
>> }
>> tdc->busy = false;
>> +
>> + pm_runtime_put(tdc->tdma->dev);
>> }
>>
>> static void tegra_dma_start(struct tegra_dma_channel *tdc,
>> @@ -500,18 +502,25 @@ static void tegra_dma_configure_for_next(struct tegra_dma_channel *tdc,
>> tegra_dma_resume(tdc);
>> }
>>
>> -static void tdc_start_head_req(struct tegra_dma_channel *tdc)
>> +static bool tdc_start_head_req(struct tegra_dma_channel *tdc)
>> {
>> struct tegra_dma_sg_req *sg_req;
>> + int err;
>>
>> if (list_empty(&tdc->pending_sg_req))
>> - return;
>> + return false;
>> +
>> + err = pm_runtime_get_sync(tdc->tdma->dev);
>> + if (WARN_ON_ONCE(err < 0))
>> + return false;
>>
>> sg_req = list_first_entry(&tdc->pending_sg_req, typeof(*sg_req), node);
>> tegra_dma_start(tdc, sg_req);
>> sg_req->configured = true;
>> sg_req->words_xferred = 0;
>> tdc->busy = true;
>> +
>> + return true;
>> }
>>
>> static void tdc_configure_next_head_desc(struct tegra_dma_channel *tdc)
>> @@ -615,6 +624,8 @@ static void handle_once_dma_done(struct tegra_dma_channel *tdc,
>> }
>> list_add_tail(&sgreq->node, &tdc->free_sg_req);
>>
>> + pm_runtime_put(tdc->tdma->dev);
>> +
>> /* Do not start DMA if it is going to be terminate */
>> if (to_terminate || list_empty(&tdc->pending_sg_req))
>> return;
>> @@ -730,9 +741,7 @@ static void tegra_dma_issue_pending(struct dma_chan *dc)
>> dev_err(tdc2dev(tdc), "No DMA request\n");
>> goto end;
>> }
>> - if (!tdc->busy) {
>> - tdc_start_head_req(tdc);
>> -
>> + if (!tdc->busy && tdc_start_head_req(tdc)) {
>> /* Continuous single mode: Configure next req */
>> if (tdc->cyclic) {
>> /*
>> @@ -775,6 +784,13 @@ static int tegra_dma_terminate_all(struct dma_chan *dc)
>> else
>> wcount = status;
>>
>> + /*
>> + * tegra_dma_stop() will drop the RPM's usage refcount, but
>> + * tegra_dma_resume() touches hardware and thus we should keep
>> + * the DMA clock active while it's needed.
>> + */
>> + pm_runtime_get(tdc->tdma->dev);
>> +
>
> Would it work and make it simpler to just enable in the issue_pending
> and disable in the handle_once_dma_done or terminate_all?
>
> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> index 3a45079d11ec..86bbb45da93d 100644
> --- a/drivers/dma/tegra20-apb-dma.c
> +++ b/drivers/dma/tegra20-apb-dma.c
> @@ -616,9 +616,14 @@ static void handle_once_dma_done(struct
> tegra_dma_channel *tdc,
> list_add_tail(&sgreq->node, &tdc->free_sg_req);
>
> /* Do not start DMA if it is going to be terminate */
> - if (to_terminate || list_empty(&tdc->pending_sg_req))
> + if (to_terminate)
> return;
>
> + if (list_empty(&tdc->pending_sg_req)) {
> + pm_runtime_put(tdc->tdma->dev);
> + return;
> + }
> +
> tdc_start_head_req(tdc);
> }
>
> @@ -729,6 +734,11 @@ static void tegra_dma_issue_pending(struct dma_chan
> *dc)
> goto end;
> }
> if (!tdc->busy) {
> + if (pm_runtime_get_sync(tdc->tdma->dev) < 0) {
> + dev_err(tdc2dev(tdc), "Failed to enable DMA!\n");
> + goto end;
> + }
> +
> tdc_start_head_req(tdc);
>
> /* Continuous single mode: Configure next req */
> @@ -788,6 +798,7 @@ static int tegra_dma_terminate_all(struct dma_chan *dc)
> get_current_xferred_count(tdc, sgreq,
> wcount);
> }
> tegra_dma_resume(tdc);
> + pm_runtime_put(tdc->tdma->dev);
>
> skip_dma_stop:
> tegra_dma_abort_all(tdc);
>
The tegra_dma_stop() should put RPM anyways, which is missed in yours
sample. Please see handle_continuous_head_request().
I'm also finding the explicit get/put a bit easier to follow in the
code, don't you think so?
next prev parent reply other threads:[~2020-01-30 16:12 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 [this message]
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
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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