On Tue, May 19, 2020 at 10:37:14PM +0530, Vinod Koul wrote: > On 17-05-20, 22:38, Serge Semin wrote: > > On Fri, May 15, 2020 at 12:09:50PM +0530, Vinod Koul wrote: > > > On 12-05-20, 22:12, Andy Shevchenko wrote: > > > > On Tue, May 12, 2020 at 05:08:20PM +0300, Serge Semin wrote: > > > > > On Fri, May 08, 2020 at 02:41:53PM +0300, Andy Shevchenko wrote: > > > > > > On Fri, May 08, 2020 at 01:53:03PM +0300, Serge Semin wrote: [nip] > > > > > > But let's see what we can do better. Since maximum is defined on the slave side > > > > > > device, it probably needs to define minimum as well, otherwise it's possible > > > > > > that some hardware can't cope underrun bursts. > > > > > > > > > > There is no need to define minimum if such limit doesn't exists except a > > > > > natural 1. Moreover it doesn't exist for all DMA controllers seeing noone has > > > > > added such capability into the generic DMA subsystem so far. > > > > > > > > There is a contract between provider and consumer about DMA resource. That's > > > > why both sides should participate in fulfilling it. Theoretically it may be a > > > > hardware that doesn't support minimum burst available in DMA by a reason. For > > > > such we would need minimum to be provided as well. > > > > > > Agreed and if required caps should be extended to tell consumer the > > > minimum values supported. > > > > Sorry, it's not required by our hardware. Is there any, which actually has such > > limitation? (minimum burst length) > > IIUC the idea is that you will tell maximum and minimum values supported > and client can pick the best value. Esp in case of slave transfers > things like burst, msize are governed by client capability and usage. So > exposing the set to pick from would make sense Agreed. I'll add min_burst capability. -Sergey > > -- > ~Vinod
