linux-kernel - Re: [PATCH] Revert "dmaengine: dw: Enable runtime PM"

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Date:   Wed, 3 Feb 2021 19:06:03 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Cezary Rojewski <cezary.rojewski@...el.com>
Cc:     dmaengine <dmaengine@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        viresh kumar <vireshk@...nel.org>,
        Vinod Koul <vkoul@...nel.org>
Subject: Re: [PATCH] Revert "dmaengine: dw: Enable runtime PM"

On Wed, Feb 3, 2021 at 5:53 PM Cezary Rojewski
<cezary.rojewski@...el.com> wrote:
>
> This reverts commit 842067940a3e3fc008a60fee388e000219b32632.
> For some solutions e.g. sound/soc/intel/catpt, DW DMA is part of a
> compound device (in that very example, domains: ADSP, SSP0, SSP1, DMA0
> and DMA1 are part of a single entity) rather than being a standalone
> one. Driver for said device may enlist DMA to transfer data during
> suspend or resume sequences.
>
> Manipulating RPM explicitly in dw's DMA request and release channel
> functions causes suspend() to also invoke resume() for the exact same
> device. Similar situation occurs for resume() sequence. Effectively
> renders device dysfunctional after first suspend() attempt. Revert the
> change to address the problem.

I kinda had the mixed feelings about this, thanks for the report.
Acked-by: Andy Shevchenko <andy.shevchenko@...il.com>

Fixes tag?

> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Signed-off-by: Cezary Rojewski <cezary.rojewski@...el.com>
> ---
>  drivers/dma/dw/core.c | 6 ------
>  1 file changed, 6 deletions(-)
>
> diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
> index 19a23767533a..7ab83fe601ed 100644
> --- a/drivers/dma/dw/core.c
> +++ b/drivers/dma/dw/core.c
> @@ -982,11 +982,8 @@ static int dwc_alloc_chan_resources(struct dma_chan *chan)
>
>         dev_vdbg(chan2dev(chan), "%s\n", __func__);
>
> -       pm_runtime_get_sync(dw->dma.dev);
> -
>         /* ASSERT:  channel is idle */
>         if (dma_readl(dw, CH_EN) & dwc->mask) {
> -               pm_runtime_put_sync_suspend(dw->dma.dev);
>                 dev_dbg(chan2dev(chan), "DMA channel not idle?\n");
>                 return -EIO;
>         }
> @@ -1003,7 +1000,6 @@ static int dwc_alloc_chan_resources(struct dma_chan *chan)
>          * We need controller-specific data to set up slave transfers.
>          */
>         if (chan->private && !dw_dma_filter(chan, chan->private)) {
> -               pm_runtime_put_sync_suspend(dw->dma.dev);
>                 dev_warn(chan2dev(chan), "Wrong controller-specific data\n");
>                 return -EINVAL;
>         }
> @@ -1047,8 +1043,6 @@ static void dwc_free_chan_resources(struct dma_chan *chan)
>         if (!dw->in_use)
>                 do_dw_dma_off(dw);
>
> -       pm_runtime_put_sync_suspend(dw->dma.dev);
> -
>         dev_vdbg(chan2dev(chan), "%s: done\n", __func__);
>  }
>
> --
> 2.17.1
>


-- 
With Best Regards,
Andy Shevchenko