On 07/24/2013 10:28 AM, Fernandes, Joel wrote: > > On Jul 24, 2013, at 3:23 AM, "Lars-Peter Clausen" <lars@xxxxxxxxxx> wrote: > >> On 07/24/2013 10:11 AM, Joel Fernandes wrote: >>> On 07/24/2013 03:03 AM, Lars-Peter Clausen wrote: >>>> On 07/23/2013 06:43 PM, Joel Fernandes wrote: >>>>> Implement device_slave_caps(). EDMA has a limited number of slots. >>>>> Slave drivers such as omap_hsmmc will query the driver to make >>>>> sure they don't pass in more than these many scatter segments. >>>>> >>>>> Signed-off-by: Joel Fernandes <joelf@xxxxxx> >>>>> --- >>>>> Vinod, or Dan- If this patch looks ok, can you please merge in for >>>>> -rc cycle? This patch is required to fix MMC support on AM33xx. This >>>>> patch is blocking 3 other patches which fix various MMC things. Thanks! >>>>> >>>>> Notes: >>>>> (1) this approach is temporary and only for -rc cycle to fix MMC on >>>>> AM335x. It will be replace by the RFC series in future kernels: >>>>> http://www.spinics.net/lists/arm-kernel/msg260094.html >>>>> >>>>> (2) Patch depends Vinod's patch at: >>>>> http://permalink.gmane.org/gmane.linux.kernel/1525112 >>>>> >>>>> drivers/dma/edma.c | 9 +++++++++ >>>>> 1 file changed, 9 insertions(+) >>>>> >>>>> diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c >>>>> index 7222cbe..81d5429 100644 >>>>> --- a/drivers/dma/edma.c >>>>> +++ b/drivers/dma/edma.c >>>>> @@ -517,6 +517,14 @@ static void edma_issue_pending(struct dma_chan *chan) >>>>> spin_unlock_irqrestore(&echan->vchan.lock, flags); >>>>> } >>>>> >>>>> +static inline int edma_slave_caps(struct dma_chan *chan, >>>>> + struct dma_slave_caps *caps) >>>>> +{ >>>>> + caps->max_sg_nr = MAX_NR_SG; >>>> >>>> Hm, what about the other fields? >>> >>> Other fields are unused, the max segment size is supposed to be >>> calculated "given" the address width and burst size. Since these >>> can't be provided to get_caps, I have left it out for now. >>> See: https://lkml.org/lkml/2013/3/6/464 >> >> The PL330 driver is similar in this regard, the maximum segment size also >> depends on address width and burst width. What I did for the get_slave_caps >> implementation is to set it to the minimum maximum size. E.g. in you case >> that should be SZ_64K - 1 (burstsize and addrwidth both set to 1). > > So you're setting max to minimum maximum size? Isn't that like telling the driver that its segments can't be bigger than this... Unless I'm missing something.. Yes. This is a limitation of the current slave_caps API. The maximum needs to be the maximum for all possible configurations. A specific configuration may allow a larger maximum. So we maybe have to extend the API to be able to query the limits for a certain configuration. Not sure what the best way would be to do that, either adding a config parameter to get_slave_caps or to break it into two functions like you proposed one for the static capabilities and one for the sg limits. > >> >>> >>> Even if it did, the "segment size" itself is unused in the MMC driver >>> that this is supposed to fix, unlike the "number of segments" which I'm >>> populating above. >> >> E.g. for ALSA we'll need to know the max segment size, so I think it doesn't >> hurt add this in this patch as well. > > For alsa it would dma only the minimum max size even if the dma controller could do more? > Yes, but I think 64k is still plenty enough for the max period size. The current davinci PCM driver even claims to only support up to 8k. - Lars -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
