linux-kernel - Re: [PATCH v4 11/14] dmaengine: tegra-apb: Clean up suspend-resume

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Date:   Tue, 28 Jan 2020 14:10:24 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
CC:     <dmaengine@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 11/14] dmaengine: tegra-apb: Clean up suspend-resume


On 21/01/2020 21:23, Dmitry Osipenko wrote:
> 12.01.2020 20:30, Dmitry Osipenko пишет:
>> It is enough to check whether hardware is busy on suspend and to reset
>> it across of suspend-resume because channel's configuration is fully
>> re-programmed on each DMA transaction anyways and because save-restore
>> of an active channel won't end up well without pausing transfer prior to
>> saving of the state (note that all channels shall be idling at the time of
>> suspend, so save-restore is not needed at all).
>>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>  drivers/dma/tegra20-apb-dma.c | 131 +++++++++++++++++-----------------
>>  1 file changed, 67 insertions(+), 64 deletions(-)
>>
>> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
>> index b9d8e57eaf54..398a0e1d6506 100644
>> --- a/drivers/dma/tegra20-apb-dma.c
>> +++ b/drivers/dma/tegra20-apb-dma.c
>> @@ -1392,6 +1392,36 @@ static const struct tegra_dma_chip_data tegra148_dma_chip_data = {
>>  	.support_separate_wcount_reg = true,
>>  };
>>  
>> +static int tegra_dma_init_hw(struct tegra_dma *tdma)
>> +{
>> +	int err;
>> +
>> +	err = reset_control_assert(tdma->rst);
>> +	if (err) {
>> +		dev_err(tdma->dev, "failed to assert reset: %d\n", err);
>> +		return err;
>> +	}
>> +
>> +	err = clk_enable(tdma->dma_clk);
>> +	if (err) {
>> +		dev_err(tdma->dev, "failed to enable clk: %d\n", err);
>> +		return err;
>> +	}
>> +
>> +	/* reset DMA controller */
>> +	udelay(2);
>> +	reset_control_deassert(tdma->rst);
>> +
>> +	/* enable global DMA registers */
>> +	tdma_write(tdma, TEGRA_APBDMA_GENERAL, TEGRA_APBDMA_GENERAL_ENABLE);
>> +	tdma_write(tdma, TEGRA_APBDMA_CONTROL, 0);
>> +	tdma_write(tdma, TEGRA_APBDMA_IRQ_MASK_SET, 0xFFFFFFFF);
>> +
>> +	clk_disable(tdma->dma_clk);
>> +
>> +	return 0;
>> +}
>> +
>>  static int tegra_dma_probe(struct platform_device *pdev)
>>  {
>>  	const struct tegra_dma_chip_data *cdata;
>> @@ -1433,30 +1463,18 @@ static int tegra_dma_probe(struct platform_device *pdev)
>>  	if (ret)
>>  		return ret;
>>  
>> +	ret = tegra_dma_init_hw(tdma);
>> +	if (ret)
>> +		goto err_clk_unprepare;
>> +
>>  	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)
>>  			goto err_clk_unprepare;
> 
> Jon, but isn't the RPM mandatory for all Tegra SoCs now and thus
> guaranteed to be enabled? Maybe we should start to remove handling the
> case of unavailable RPM from all Tegra drivers?

Yes that's true, even ARCH_TEGRA selects PM now

Cheers
Jon

-- 
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