Re: [PATCH v4 10/14] dmaengine: tegra-apb: Keep clock enabled only during of DMA transfer

Dmitry Osipenko
2020-01-16T19:07:54Z

15.01.2020 13:08, Jon Hunter пишет:
>
>
> On 12/01/2020 17:30, 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 | 43 ++++++++++++++++++++++-------------
>> 1 file changed, 27 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
>> index cc4a9ca20780..b9d8e57eaf54 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);
>
> Is this the right place to call put? Seems that in terminate_all resume
> is called after stop which will access the registers.

Indeed, there is a problem here. Looks like resume/pause should take
get/put the RPM. I'll correct it in v5, thanks.

>> }
>>
>> 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) {
>> /*
>> @@ -1280,22 +1289,15 @@ tegra_dma_prep_dma_cyclic(struct dma_chan *dc, dma_addr_t buf_addr,
>> static int tegra_dma_alloc_chan_resources(struct dma_chan *dc)
>> {
>> struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
>> - struct tegra_dma *tdma = tdc->tdma;
>> - int ret;
>>
>> dma_cookie_init(&tdc->dma_chan);
>>
>> - ret = pm_runtime_get_sync(tdma->dev);
>> - if (ret < 0)
>> - return ret;
>> -
>> return 0;
>> }
>>
>> static void tegra_dma_free_chan_resources(struct dma_chan *dc)
>> {
>> struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
>> - struct tegra_dma *tdma = tdc->tdma;
>> struct tegra_dma_desc *dma_desc;
>> struct tegra_dma_sg_req *sg_req;
>> struct list_head dma_desc_list;
>> @@ -1328,7 +1330,6 @@ static void tegra_dma_free_chan_resources(struct dma_chan *dc)
>> list_del(&sg_req->node);
>> kfree(sg_req);
>> }
>> - pm_runtime_put(tdma->dev);
>>
>> tdc->slave_id = TEGRA_APBDMA_SLAVE_ID_INVALID;
>> }
>> @@ -1428,11 +1429,16 @@ static int tegra_dma_probe(struct platform_device *pdev)
>>
>> spin_lock_init(&tdma->global_lock);
>>
>> + ret = clk_prepare(tdma->dma_clk);
>> + if (ret)
>> + return ret;
>> +
>> + pm_runtime_irq_safe(&pdev->dev);
>> pm_runtime_enable(&pdev->dev);
>> if (!pm_runtime_enabled(&pdev->dev)) {
>> ret = tegra_dma_runtime_resume(&pdev->dev);
>> if (ret)
>> - return ret;
>> + goto err_clk_unprepare;
>> } else {
>> ret = pm_runtime_get_sync(&pdev->dev);
>
> There is a get here but I don't see a put in probe.