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Message-ID: <20120801173059.GF11359@ovro.caltech.edu>
Date: Wed, 1 Aug 2012 10:30:59 -0700
From: "Ira W. Snyder" <iws@...o.caltech.edu>
To: qiang.liu@...escale.com
Cc: linux-crypto@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
linux-kernel@...r.kernel.org, dan.j.williams@...il.com,
Vinod Koul <vinod.koul@...el.com>,
Timur Tabi <timur@...escale.com>, herbert@...dor.hengli.com.au,
Dan Williams <dan.j.williams@...el.com>, davem@...emloft.net
Subject: Re: [PATCH v5 5/6] fsl-dma: use spin_lock_bh to instead of
spin_lock_irqsave
On Wed, Aug 01, 2012 at 04:50:09PM +0800, qiang.liu@...escale.com wrote:
> From: Qiang Liu <qiang.liu@...escale.com>
>
> - use spin_lock_bh() is the right way to use async_tx api,
> dma_run_dependencies() should not be protected by spin_lock_irqsave();
> - use spin_lock_bh to instead of spin_lock_irqsave for improving performance,
> There is not any place to access descriptor queues in fsl-dma ISR except its
> tasklet, spin_lock_bh() is more proper here. Interrupts will be turned off and
> context will be save in irqsave, there is needless to use irqsave..
>
This description is not very clear English. I understand it is not your
native language. Let me try to help.
"""
The use of spin_lock_irqsave() is a stronger locking mechanism than is
required throughout the driver. The minimum locking required should be
used instead.
Change all instances of spin_lock_irqsave() to spin_lock_bh(). All
manipulation of protected fields is done using tasklet context or
weaker, which makes spin_lock_bh() the correct choice.
"""
Other than that,
Acked-by: Ira W. Snyder <iws@...o.caltech.edu>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Vinod Koul <vinod.koul@...el.com>
> Cc: Li Yang <leoli@...escale.com>
> Cc: Timur Tabi <timur@...escale.com>
> Signed-off-by: Qiang Liu <qiang.liu@...escale.com>
> ---
> drivers/dma/fsldma.c | 30 ++++++++++++------------------
> 1 files changed, 12 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
> index bb883c0..e3814aa 100644
> --- a/drivers/dma/fsldma.c
> +++ b/drivers/dma/fsldma.c
> @@ -645,10 +645,9 @@ static dma_cookie_t fsl_dma_tx_submit(struct dma_async_tx_descriptor *tx)
> struct fsldma_chan *chan = to_fsl_chan(tx->chan);
> struct fsl_desc_sw *desc = tx_to_fsl_desc(tx);
> struct fsl_desc_sw *child;
> - unsigned long flags;
> dma_cookie_t cookie;
>
> - spin_lock_irqsave(&chan->desc_lock, flags);
> + spin_lock_bh(&chan->desc_lock);
>
> /*
> * assign cookies to all of the software descriptors
> @@ -661,7 +660,7 @@ static dma_cookie_t fsl_dma_tx_submit(struct dma_async_tx_descriptor *tx)
> /* put this transaction onto the tail of the pending queue */
> append_ld_queue(chan, desc);
>
> - spin_unlock_irqrestore(&chan->desc_lock, flags);
> + spin_unlock_bh(&chan->desc_lock);
>
> return cookie;
> }
> @@ -770,15 +769,14 @@ static void fsldma_free_desc_list_reverse(struct fsldma_chan *chan,
> static void fsl_dma_free_chan_resources(struct dma_chan *dchan)
> {
> struct fsldma_chan *chan = to_fsl_chan(dchan);
> - unsigned long flags;
>
> chan_dbg(chan, "free all channel resources\n");
> - spin_lock_irqsave(&chan->desc_lock, flags);
> + spin_lock_bh(&chan->desc_lock);
> fsldma_cleanup_descriptor(chan);
> fsldma_free_desc_list(chan, &chan->ld_pending);
> fsldma_free_desc_list(chan, &chan->ld_running);
> fsldma_free_desc_list(chan, &chan->ld_completed);
> - spin_unlock_irqrestore(&chan->desc_lock, flags);
> + spin_unlock_bh(&chan->desc_lock);
>
> dma_pool_destroy(chan->desc_pool);
> chan->desc_pool = NULL;
> @@ -997,7 +995,6 @@ static int fsl_dma_device_control(struct dma_chan *dchan,
> {
> struct dma_slave_config *config;
> struct fsldma_chan *chan;
> - unsigned long flags;
> int size;
>
> if (!dchan)
> @@ -1007,7 +1004,7 @@ static int fsl_dma_device_control(struct dma_chan *dchan,
>
> switch (cmd) {
> case DMA_TERMINATE_ALL:
> - spin_lock_irqsave(&chan->desc_lock, flags);
> + spin_lock_bh(&chan->desc_lock);
>
> /* Halt the DMA engine */
> dma_halt(chan);
> @@ -1017,7 +1014,7 @@ static int fsl_dma_device_control(struct dma_chan *dchan,
> fsldma_free_desc_list(chan, &chan->ld_running);
> chan->idle = true;
>
> - spin_unlock_irqrestore(&chan->desc_lock, flags);
> + spin_unlock_bh(&chan->desc_lock);
> return 0;
>
> case DMA_SLAVE_CONFIG:
> @@ -1059,11 +1056,10 @@ static int fsl_dma_device_control(struct dma_chan *dchan,
> static void fsl_dma_memcpy_issue_pending(struct dma_chan *dchan)
> {
> struct fsldma_chan *chan = to_fsl_chan(dchan);
> - unsigned long flags;
>
> - spin_lock_irqsave(&chan->desc_lock, flags);
> + spin_lock_bh(&chan->desc_lock);
> fsl_chan_xfer_ld_queue(chan);
> - spin_unlock_irqrestore(&chan->desc_lock, flags);
> + spin_unlock_bh(&chan->desc_lock);
> }
>
> /**
> @@ -1076,15 +1072,14 @@ static enum dma_status fsl_tx_status(struct dma_chan *dchan,
> {
> struct fsldma_chan *chan = to_fsl_chan(dchan);
> enum dma_status ret;
> - unsigned long flags;
>
> ret = dma_cookie_status(dchan, cookie, txstate);
> if (ret == DMA_SUCCESS)
> return ret;
>
> - spin_lock_irqsave(&chan->desc_lock, flags);
> + spin_lock_bh(&chan->desc_lock);
> fsldma_cleanup_descriptor(chan);
> - spin_unlock_irqrestore(&chan->desc_lock, flags);
> + spin_unlock_bh(&chan->desc_lock);
>
> return dma_cookie_status(dchan, cookie, txstate);
> }
> @@ -1163,11 +1158,10 @@ static irqreturn_t fsldma_chan_irq(int irq, void *data)
> static void dma_do_tasklet(unsigned long data)
> {
> struct fsldma_chan *chan = (struct fsldma_chan *)data;
> - unsigned long flags;
>
> chan_dbg(chan, "tasklet entry\n");
>
> - spin_lock_irqsave(&chan->desc_lock, flags);
> + spin_lock_bh(&chan->desc_lock);
>
> /* the hardware is now idle and ready for more */
> chan->idle = true;
> @@ -1175,7 +1169,7 @@ static void dma_do_tasklet(unsigned long data)
> /* Run all cleanup for this descriptor */
> fsldma_cleanup_descriptor(chan);
>
> - spin_unlock_irqrestore(&chan->desc_lock, flags);
> + spin_unlock_bh(&chan->desc_lock);
>
> chan_dbg(chan, "tasklet exit\n");
> }
> --
> 1.7.5.1
>
>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@...ts.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
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