Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 18 Apr 2024 10:35:44 -0700 | Subject | Re: [PATCH V10 1/1] dmaengine: amd: qdma: Add AMD QDMA driver | From | Lizhi Hou <> |
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On 4/18/24 10:08, Vinod Koul wrote: > On 17-04-24, 10:53, Lizhi Hou wrote: >> On 4/17/24 10:03, Vinod Koul wrote: >>> On 08-04-24, 11:06, Lizhi Hou wrote: >>> >>>>>> +static void *qdma_get_metadata_ptr(struct dma_async_tx_descriptor *tx, >>>>>> + size_t *payload_len, size_t *max_len) >>>>>> +{ >>>>>> + struct qdma_mm_vdesc *vdesc; >>>>>> + >>>>>> + vdesc = container_of(tx, typeof(*vdesc), vdesc.tx); >>>>>> + if (payload_len) >>>>>> + *payload_len = sizeof(vdesc->dev_addr); >>>>>> + if (max_len) >>>>>> + *max_len = sizeof(vdesc->dev_addr); >>>>>> + >>>>>> + return &vdesc->dev_addr; >>>>> Can you describe what metadata is being used here for? >>>> The metadata is the device address the dma request will transfer >>>> >>>> data to / from. Please see the example usage here: >>>> >>>> https://github.com/houlz0507/XRT-1/blob/qdma_v1_usage/src/runtime_src/core/pcie/driver/linux/xocl/subdev/qdma.c#L311 >>>> >>>> Before dmaengine_submit(), it specifies the device address. >>> Hmmm, why is the vaddr passed like this, why not use slave_config for >>> this >>> >> This is because the hardware is capable to process multiple vdesc at one >> kick off. >> >> For example, there are two pending vdesc: vd1 and vd2. If there is enough >> free >> >> space in hardware queue, the vd1 and vd2 can be put in queue, and do one >> kick off >> >> to transfer both vd1 and vd2. >> >> The destination device address of vd1 and vd2 could be any valid device >> address. >> >> desc_metadata_ptr seems helpful for the per vdesc destination device >> address. >> >> >> If using slave_config, it needs to call dmaengine_slave_config() and > That would be the right thing to do... > > - set parameters and call dmaengine_slave_config() > - prep transfer for vd1 dmaengine_prep_slave_sg() > - set parameters and call dmaengine_slave_config() > - prep transfer for vd2 dmaengine_prep_slave_sg() > - submit vd1 > - submit vd2 > - issue_pending > - you see you can issue both as you have space, so do that > > This should be done always to maximize the dmaengine thoroughput
Thanks for your comments. I will change this.
Lizhi
> >> dmaengine_prep_slave_sg() with a lock protection. Is this what you would >> recommend? >> >> >> Thanks, >> >> Lizhi
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