Hi Vinod,
> Hmmm, why is threading broken in this series?
> Also why is this PATCH 1/6 whereas the rest of series is v3!
>
> Right way is to let git do this for you and use git format-patch
> --subject-prefix="PATCH v3"...
>
> You don't do these things manually, that would be terrible waste of time
>
> Also use git send-email to keep threading
I will keep that in mind
>> +#define NR_READS_TO_WAIT 5 /* number of times to check if DE = 0 */
>> +static inline int rcar_dmac_wait_stop(struct rcar_dmac_chan *chan)
>> +{
>> + unsigned int i = 0;
>> +
>> + do {
>> + u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
>> +
>> + if (!(chcr & RCAR_DMACHCR_DE))
>> + return 0;
>> + cpu_relax();
>> + dev_dbg(chan->chan.device->dev, "DMA xfer couldn't be stopped");
>
> And user has no way of knowing this on production system
What do you suggest here instead?
>> +/* Called with chan lock held */
>> +static int rcar_dmac_chan_halt(struct rcar_dmac_chan *chan)
>> {
>> - u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
>> + u32 chcr;
>> + int ret;
>>
>> + chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
>> chcr &= ~(RCAR_DMACHCR_DSE | RCAR_DMACHCR_DSIE | RCAR_DMACHCR_IE |
>> RCAR_DMACHCR_TE | RCAR_DMACHCR_DE);
>> rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr);
>> + ret = rcar_dmac_wait_stop(chan);
>> +
>> + WARN_ON(ret < 0);
>
> What if we have broken board and will see dmesg storm for this, perhaps
> WARN_ON_ONCE and also would be helpful to use the verbose version and print
> some meaningful message
Yes that does make sense. I shall update it in next version
Thanks for the comments
Best,
Hamza
On Mon, Oct 12, 2015 at 4:59 PM, Vinod Koul <vinod.koul@xxxxxxxxx> wrote:
> On Tue, Sep 29, 2015 at 10:44:43PM +0200, hamzahfrq.sub@xxxxxxxxx wrote:
>> From: Muhammad Hamza Farooq <mfarooq@xxxxxxxxxxx>
>>
>> DMA engine does not stop instantaneously when transaction is going on
>> (see datasheet). Wait has been added
>
> Hmmm, why is threading broken in this series?
> Also why is this PATCH 1/6 whereas the rest of series is v3!
>
> Right way is to let git do this for you and use git format-patch
> --subject-prefix="PATCH v3"...
>
> You don't do these things manually, that would be terrible waste of time
>
> Also use git send-email to keep threading
>
>> Signed-off-by: Muhammad Hamza Farooq <mfarooq@xxxxxxxxxxx>
>> ---
>> drivers/dma/sh/rcar-dmac.c | 28 ++++++++++++++++++++++++++--
>> 1 file changed, 26 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
>> index 7820d07..2b28291 100644
>> --- a/drivers/dma/sh/rcar-dmac.c
>> +++ b/drivers/dma/sh/rcar-dmac.c
>> @@ -716,14 +716,38 @@ static int rcar_dmac_fill_hwdesc(struct rcar_dmac_chan *chan,
>> /* -----------------------------------------------------------------------------
>> * Stop and reset
>> */
>> +#define NR_READS_TO_WAIT 5 /* number of times to check if DE = 0 */
>> +static inline int rcar_dmac_wait_stop(struct rcar_dmac_chan *chan)
>> +{
>> + unsigned int i = 0;
>> +
>> + do {
>> + u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
>> +
>> + if (!(chcr & RCAR_DMACHCR_DE))
>> + return 0;
>> + cpu_relax();
>> + dev_dbg(chan->chan.device->dev, "DMA xfer couldn't be stopped");
>
> And user has no way of knowing this on production system
>
>> + } while (++i < NR_READS_TO_WAIT);
>>
>> -static void rcar_dmac_chan_halt(struct rcar_dmac_chan *chan)
>> + return -EBUSY;
>> +}
>> +
>> +/* Called with chan lock held */
>> +static int rcar_dmac_chan_halt(struct rcar_dmac_chan *chan)
>> {
>> - u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
>> + u32 chcr;
>> + int ret;
>>
>> + chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
>> chcr &= ~(RCAR_DMACHCR_DSE | RCAR_DMACHCR_DSIE | RCAR_DMACHCR_IE |
>> RCAR_DMACHCR_TE | RCAR_DMACHCR_DE);
>> rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr);
>> + ret = rcar_dmac_wait_stop(chan);
>> +
>> + WARN_ON(ret < 0);
>
> What if we have broken board and will see dmesg storm for this, perhaps
> WARN_ON_ONCE and also would be helpful to use the verbose version and print
> some meaningful message
>
> --
> ~Vinod
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