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From:   Han Xu <xhnjupt@gmail.com>
Date:   Thu, 16 Jan 2020 10:36:33 -0600
Message-ID: <CA+EcR23TCUU83Y7BYX5LCvGAj20+s67n+rWaGR5R9BSMHUH82A@mail.gmail.com>
Subject: Re: [PATCH 3/6] dmaengine: mxs: add the power management functions
To:     Sascha Hauer <s.hauer@pengutronix.de>
Cc:     Han Xu <han.xu@nxp.com>, Vignesh Raghavendra <vigneshr@ti.com>,
        Richard Weinberger <richard@nod.at>,
        Esben Haabendal <esben@geanix.com>,
        linux-kernel@vger.kernel.org, vkoul@kernel.org,
        Boris Brezillon <boris.brezillon@collabora.com>,
        linux-mtd <linux-mtd@lists.infradead.org>, linux-imx@nxp.com,
        Fabio Estevam <festevam@gmail.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        dmaengine@vger.kernel.org, Shawn Guo <shawnguo@kernel.org>,
        linux-arm-kernel@lists.infradead.org
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On Wed, Jan 15, 2020 at 2:03 AM Sascha Hauer <s.hauer@pengutronix.de> wrote:
>
> On Wed, Jan 15, 2020 at 05:44:00AM +0800, Han Xu wrote:
> > add the power management functions and leverage the runtime pm for
> > system suspend/resume
> >
> > Signed-off-by: Han Xu <han.xu@nxp.com>
> > ---
> >  drivers/dma/mxs-dma.c | 97 +++++++++++++++++++++++++++++++++++++++----
> >  1 file changed, 90 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c
> > index b458f06f9067..251492c5ea58 100644
> > --- a/drivers/dma/mxs-dma.c
> > +++ b/drivers/dma/mxs-dma.c
> > @@ -25,6 +25,7 @@
> >  #include <linux/of_dma.h>
> >  #include <linux/list.h>
> >  #include <linux/dma/mxs-dma.h>
> > +#include <linux/pm_runtime.h>
> >
> >  #include <asm/irq.h>
> >
> > @@ -39,6 +40,8 @@
> >  #define dma_is_apbh(mxs_dma) ((mxs_dma)->type == MXS_DMA_APBH)
> >  #define apbh_is_old(mxs_dma) ((mxs_dma)->dev_id == IMX23_DMA)
> >
> > +#define MXS_DMA_RPM_TIMEOUT 50 /* ms */
> > +
> >  #define HW_APBHX_CTRL0                               0x000
> >  #define BM_APBH_CTRL0_APB_BURST8_EN          (1 << 29)
> >  #define BM_APBH_CTRL0_APB_BURST_EN           (1 << 28)
> > @@ -416,6 +419,7 @@ static int mxs_dma_alloc_chan_resources(struct dma_chan *chan)
> >  {
> >       struct mxs_dma_chan *mxs_chan = to_mxs_dma_chan(chan);
> >       struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma;
> > +     struct device *dev = &mxs_dma->pdev->dev;
> >       int ret;
> >
> >       mxs_chan->ccw = dma_alloc_coherent(mxs_dma->dma_device.dev,
> > @@ -431,9 +435,11 @@ static int mxs_dma_alloc_chan_resources(struct dma_chan *chan)
> >       if (ret)
> >               goto err_irq;
> >
> > -     ret = clk_prepare_enable(mxs_dma->clk);
> > -     if (ret)
> > +     ret = pm_runtime_get_sync(dev);
> > +     if (ret < 0) {
> > +             dev_err(dev, "Failed to enable clock\n");
> >               goto err_clk;
>
> From looking at other DMA drivers I know we are in good company here,
> but I think this is wrong. Doing pm_runtime_get_sync() in
> alloc_chan_resources() and going to autosuspend in free_chan_resources()
> effectively disables runtime_pm as clients normally acquire their
> channels during driver probe and release them only in driver remove.

Thanks for the comments.
That's why I moved acquire_dma_resource from the probe to
runtime_resume in the gpmi driver, this change won't disable the
runtime_pm function and the incremental counter always balanced.

>
> In the next patch you release the DMA channels in the GPMI nand drivers
> runtime_suspend hook just to somehow trigger the runtime_suspend of the
> DMA driver.
>
> What you should do instead is to make sure the hook runtime_pm to the
> DMA drivers activity phases, like for example the pl330 driver does.
> Then you wouldn't have to care about manually putting the DMA driver into
> suspend from the GPMI NAND driver.
>
> Sascha
>
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-- 
Sincerely,

Han XU