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On Jul 24, 2013, at 2:15 PM, "Lars-Peter Clausen" <l...@metafoo.de> wrote: > On 07/24/2013 08:55 PM, Joel Fernandes wrote: >> On 07/24/2013 03:40 AM, Lars-Peter Clausen wrote: >>> On 07/24/2013 10:28 AM, Fernandes, Joel wrote: >>>> >>>> On Jul 24, 2013, at 3:23 AM, "Lars-Peter Clausen" <l...@metafoo.de> 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 <jo...@ti.com> >>>>>>>> --- >>>>>>>> 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. >> >> I am OK with either approach as long as a decision can be made quickly >> by maintainers. Right now lot of back and forth has happened and 3 >> different versions of the same thing have been posted since January. >> Since this is such a trivial change, it doesn't make sense to spend so >> much time on it IMO.... The sad part is though this change is trivial, >> other drivers such as MMC are broken and cannot be enabled due to this. >> We cannot afford to leave them broken. > > Well this is a new API, so it is kind of expected that there is some back and > forth and that there will be a few revisions. Sure. Only thing bothered me is it is a few lines and is just API semantics, nothing functional really. The MMC dt patches were posted but not applied. I said regression because the dt was agreed for -rc cycle but only thing missing is this trivial api stuff so possibly counting that as a regression fixes MMC altogether. 6 months for trivial change blocking an otherwise fully working driver is too much. I am speaking collectively for all of us, not me or anyone in particular. Anyway looks like MMC is not going anywhere till then. > >> >> If Vinod is not available, can Dan please respond on how to proceed on >> this? We really need this trivial change to go into this -rc cycle and >> not delay it by another kernel release. Thank you. > > This is not something you'd merge for rc3 or even later. If the MMC driver > does not work without this I guess it never worked, so strictly speaking > there is no regression and it is just a new feature. Agreed. -Joel > > - Lars > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
