On Thu, Jan 17, 2019 at 05:10:38PM +0100, Codrin Ciubotariu - M19940 wrote:
> From: Codrin Ciubotariu <codrin.ciubota...@microchip.com>
> 
> atchan->status is used for two things:
>  - pass channel interrupts status from interrupt handler to tasklet;
>  - channel information like whether it is cyclic or paused;
> 
> Since these operations have nothing in common, this patch adds a
> different struct member to keep the interrupts status.
> 
> Fixes a bug in which a channel is wrongfully reported as in use when
> trying to obtain a new descriptior for a previously used cyclic channel.
> 
> Signed-off-by: Codrin Ciubotariu <codrin.ciubota...@microchip.com>
Acked-by: Ludovic Desroches <ludovic.desroc...@microchip.com>

As Vinod suggested, you may change the commit message to emphasize
that the bug comes from the fact that a single variable is used to store
different information.

The Fixes: tag should be added too.

Regards

Ludovic

> ---
>  drivers/dma/at_xdmac.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
> index 4e557684f792..fe69dccfa0c0 100644
> --- a/drivers/dma/at_xdmac.c
> +++ b/drivers/dma/at_xdmac.c
> @@ -203,6 +203,7 @@ struct at_xdmac_chan {
>       u32                             save_cim;
>       u32                             save_cnda;
>       u32                             save_cndc;
> +     u32                             irq_status;
>       unsigned long                   status;
>       struct tasklet_struct           tasklet;
>       struct dma_slave_config         sconfig;
> @@ -1580,8 +1581,8 @@ static void at_xdmac_tasklet(unsigned long data)
>       struct at_xdmac_desc    *desc;
>       u32                     error_mask;
>  
> -     dev_dbg(chan2dev(&atchan->chan), "%s: status=0x%08lx\n",
> -              __func__, atchan->status);
> +     dev_dbg(chan2dev(&atchan->chan), "%s: status=0x%08x\n",
> +             __func__, atchan->irq_status);
>  
>       error_mask = AT_XDMAC_CIS_RBEIS
>                    | AT_XDMAC_CIS_WBEIS
> @@ -1589,15 +1590,15 @@ static void at_xdmac_tasklet(unsigned long data)
>  
>       if (at_xdmac_chan_is_cyclic(atchan)) {
>               at_xdmac_handle_cyclic(atchan);
> -     } else if ((atchan->status & AT_XDMAC_CIS_LIS)
> -                || (atchan->status & error_mask)) {
> +     } else if ((atchan->irq_status & AT_XDMAC_CIS_LIS)
> +                || (atchan->irq_status & error_mask)) {
>               struct dma_async_tx_descriptor  *txd;
>  
> -             if (atchan->status & AT_XDMAC_CIS_RBEIS)
> +             if (atchan->irq_status & AT_XDMAC_CIS_RBEIS)
>                       dev_err(chan2dev(&atchan->chan), "read bus error!!!");
> -             if (atchan->status & AT_XDMAC_CIS_WBEIS)
> +             if (atchan->irq_status & AT_XDMAC_CIS_WBEIS)
>                       dev_err(chan2dev(&atchan->chan), "write bus error!!!");
> -             if (atchan->status & AT_XDMAC_CIS_ROIS)
> +             if (atchan->irq_status & AT_XDMAC_CIS_ROIS)
>                       dev_err(chan2dev(&atchan->chan), "request overflow 
> error!!!");
>  
>               spin_lock(&atchan->lock);
> @@ -1652,7 +1653,7 @@ static irqreturn_t at_xdmac_interrupt(int irq, void 
> *dev_id)
>                       atchan = &atxdmac->chan[i];
>                       chan_imr = at_xdmac_chan_read(atchan, AT_XDMAC_CIM);
>                       chan_status = at_xdmac_chan_read(atchan, AT_XDMAC_CIS);
> -                     atchan->status = chan_status & chan_imr;
> +                     atchan->irq_status = chan_status & chan_imr;
>                       dev_vdbg(atxdmac->dma.dev,
>                                "%s: chan%d: imr=0x%x, status=0x%x\n",
>                                __func__, i, chan_imr, chan_status);
> @@ -1666,7 +1667,7 @@ static irqreturn_t at_xdmac_interrupt(int irq, void 
> *dev_id)
>                                at_xdmac_chan_read(atchan, AT_XDMAC_CDA),
>                                at_xdmac_chan_read(atchan, AT_XDMAC_CUBC));
>  
> -                     if (atchan->status & (AT_XDMAC_CIS_RBEIS | 
> AT_XDMAC_CIS_WBEIS))
> +                     if (atchan->irq_status & (AT_XDMAC_CIS_RBEIS | 
> AT_XDMAC_CIS_WBEIS))
>                               at_xdmac_write(atxdmac, AT_XDMAC_GD, 
> atchan->mask);
>  
>                       tasklet_schedule(&atchan->tasklet);
> -- 
> 2.17.1
> 

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