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Date: Mon, 17 Sep 2018 07:51:36 +0000
From: Robin Gong <yibin.gong@....com>
To: Lucas Stach <l.stach@...gutronix.de>, Vinod Koul <vkoul@...nel.org>
CC: "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
dl-linux-imx <linux-imx@....com>,
"kernel@...gutronix.de" <kernel@...gutronix.de>,
"patchwork-lst@...gutronix.de" <patchwork-lst@...gutronix.de>
Subject: RE: [PATCH v2 3/4] dmaengine: imx-sdma: implement channel termination
via worker
> -----Original Message-----
> From: Lucas Stach <l.stach@...gutronix.de>
> Sent: 2018年9月15日 1:06
> To: Vinod Koul <vkoul@...nel.org>
> Cc: dmaengine@...r.kernel.org; linux-kernel@...r.kernel.org; Robin Gong
> <yibin.gong@....com>; dl-linux-imx <linux-imx@....com>;
> kernel@...gutronix.de; patchwork-lst@...gutronix.de
> Subject: [PATCH v2 3/4] dmaengine: imx-sdma: implement channel termination
> via worker
>
> The dmaengine documentation states that device_terminate_all may be
> asynchronous and need not wait for the active transfers have stopped.
>
> This allows us to move most of the functionality currently implemented in the
> sdma channel termination function to run in a worker, outside of any atomic
> context. Moving this out of atomic context has two
> benefits: we can now sleep while waiting for the channel to terminate, instead
> of busy waiting and the freeing of the dma descriptors happens with IRQs
> enabled, getting rid of a warning in the dma mapping code.
>
> As the termination is now asnc, we need to implement the device_synchronize
> dma engine function, which simply waits for the worker to finish its execution.
>
> Signed-off-by: Lucas Stach <l.stach@...gutronix.de>
> ---
> v2: Keep vchan_get_all_descriptors in the terminate_all call, so the
> worker doesn't corrupt the next transfer if that's already in
> the setup process.
> ---
> drivers/dma/imx-sdma.c | 42 ++++++++++++++++++++++++++++++++----------
> 1 file changed, 32 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c index
> 8d2fec8b16cc..da41e8fbf151 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -32,6 +32,7 @@
> #include <linux/of_address.h>
> #include <linux/of_device.h>
> #include <linux/of_dma.h>
> +#include <linux/workqueue.h>
>
> #include <asm/irq.h>
> #include <linux/platform_data/dma-imx-sdma.h>
> @@ -375,6 +376,8 @@ struct sdma_channel {
> u32 shp_addr, per_addr;
> enum dma_status status;
> struct imx_dma_data data;
> + struct work_struct terminate_worker;
> + struct list_head deferred_desc_list;
> };
>
> #define IMX_DMA_SG_LOOP BIT(0)
> @@ -1025,31 +1028,47 @@ static int sdma_disable_channel(struct dma_chan
> *chan)
>
> return 0;
> }
> +static void sdma_channel_terminate(struct work_struct *work) {
> + struct sdma_channel *sdmac = container_of(work, struct sdma_channel,
> + terminate_worker);
> +
> + /*
> + * According to NXP R&D team a delay of one BD SDMA cost time
> + * (maximum is 1ms) should be added after disable of the channel
> + * bit, to ensure SDMA core has really been stopped after SDMA
> + * clients call .device_terminate_all.
> + */
> + usleep_range(1000, 2000);
> +
> + vchan_dma_desc_free_list(&sdmac->vc, &sdmac->deferred_desc_list);
> + INIT_LIST_HEAD(&sdmac->deferred_desc_list);
> +}
>
> static int sdma_disable_channel_with_delay(struct dma_chan *chan) {
> struct sdma_channel *sdmac = to_sdma_chan(chan);
> unsigned long flags;
> - LIST_HEAD(head);
>
> sdma_disable_channel(chan);
> +
> spin_lock_irqsave(&sdmac->vc.lock, flags);
> - vchan_get_all_descriptors(&sdmac->vc, &head);
> + vchan_get_all_descriptors(&sdmac->vc, &sdmac->deferred_desc_list);
> sdmac->desc = NULL;
> spin_unlock_irqrestore(&sdmac->vc.lock, flags);
> - vchan_dma_desc_free_list(&sdmac->vc, &head);
>
> - /*
> - * According to NXP R&D team a delay of one BD SDMA cost time
> - * (maximum is 1ms) should be added after disable of the channel
> - * bit, to ensure SDMA core has really been stopped after SDMA
> - * clients call .device_terminate_all.
> - */
> - mdelay(1);
> + schedule_work(&sdmac->terminate_worker);
>
> return 0;
> }
>
> +static void sdma_channel_synchronize(struct dma_chan *chan) {
> + struct sdma_channel *sdmac = to_sdma_chan(chan);
> +
Please add the below to make sure internal virt dma tasklet killed too.
tasklet_kill(&sdmac->vc.task);
> + flush_work(&sdmac->terminate_worker);
> +}
> +
> static void sdma_set_watermarklevel_for_p2p(struct sdma_channel *sdmac)
> {
> struct sdma_engine *sdma = sdmac->sdma; @@ -1993,6 +2012,8 @@
> static int sdma_probe(struct platform_device *pdev)
>
> sdmac->channel = i;
> sdmac->vc.desc_free = sdma_desc_free;
> + INIT_WORK(&sdmac->terminate_worker,
> sdma_channel_terminate);
> + INIT_LIST_HEAD(&sdmac->deferred_desc_list);
> /*
> * Add the channel to the DMAC list. Do not add channel 0 though
> * because we need it internally in the SDMA driver. This also means
> @@ -2045,6 +2066,7 @@ static int sdma_probe(struct platform_device
> *pdev)
> sdma->dma_device.device_prep_dma_cyclic = sdma_prep_dma_cyclic;
> sdma->dma_device.device_config = sdma_config;
> sdma->dma_device.device_terminate_all =
> sdma_disable_channel_with_delay;
> + sdma->dma_device.device_synchronize = sdma_channel_synchronize;
> sdma->dma_device.src_addr_widths = SDMA_DMA_BUSWIDTHS;
> sdma->dma_device.dst_addr_widths = SDMA_DMA_BUSWIDTHS;
> sdma->dma_device.directions = SDMA_DMA_DIRECTIONS;
> --
> 2.19.0
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