From mboxrd@z Thu Jan 1 00:00:00 1970 From: robert.jarzmik@free.fr (Robert Jarzmik) Date: Wed, 04 Apr 2018 21:21:55 +0200 Subject: [PATCH 02/15] ARM: pxa: add dma slave map In-Reply-To: (Arnd Bergmann's message of "Wed, 4 Apr 2018 12:18:58 +0200") References: <20180402142656.26815-1-robert.jarzmik@free.fr> <20180402142656.26815-3-robert.jarzmik@free.fr> <87tvss48ti.fsf@belgarion.home> <87h8os3uwa.fsf@belgarion.home> Message-ID: <87d0ze4w18.fsf@belgarion.home> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Arnd Bergmann writes: > On Tue, Apr 3, 2018 at 10:19 PM, Robert Jarzmik wrote: >> ... chop chop removing unneeded recipients .... >> >> Arnd Bergmann writes: >>> It still feels odd to me that there is an entry in the slave map for >>> a device that does not have a request line. However, it also seems >>> that the entire code in those two drivers that deals with DMA is specific >>> to PXA anyway, so maybe it can be done differently: instead of >>> calling dma_request_slave_channel_compat() or dma_request_chan() >>> with a fake request line, how about calling dma_request_channel() >>> with an NULL filter function and data, and have the driver handle >>> the empty data case the same way as the rq=-1 case today? >> Okay, in this case : >> - the channel priority cannot be passed anymore > > Right, but it could just always use a static priority, right? Yes, an implicit default priority. I'm not a big fan of implicit parameters, yet I can do it. >> - and I don't see how this can work : >> dma_request_channel() >> __dma_request_channel() >> find_candidate() >> private_candidate(mask, device, fn, fn_param); >> /* Here, fn == NULL and fn_param == NULL as per your proposal */ >> >> This function will find the first available dma channel, all right, but >> no function will be called in pxa_dma driver, and therefore the last >> requestor of the channel will be used, which is bad. > > Can't you just reset those in pxad_free_chan_resources()? I can, let's see what happens next ... Cheers. -- Robert