On 20-07-22, 10:54, Biju Das wrote: > Hi Vinod, > > > Subject: Re: [PATCH] spi: spi-rspi: Add force_dma variable to spi_ops > > > > On 20-07-22, 05:13, Biju Das wrote: > > > Hi Vinod, > > > > > > > Subject: Re: [PATCH] spi: spi-rspi: Add force_dma variable to > > > > spi_ops > > > > > > > > On 19-07-22, 11:28, Biju Das wrote: > > > > > Hi Geert, > > > > > > > > > > +Vinod > > > > > > > > > > > Subject: Re: [PATCH] spi: spi-rspi: Add force_dma variable to > > > > > > spi_ops > > > > > > > > > > > > Hi Biju, > > > > > > > > > > > > On Tue, Jul 19, 2022 at 10:29 AM Biju Das > > > > > > <biju.das.jz@xxxxxxxxxxxxxx> > > > > > > wrote: > > > > > > > > Subject: Re: [PATCH] spi: spi-rspi: Add force_dma variable > > > > > > > > to spi_ops On Sat, Jul 16, 2022 at 5:39 PM Biju Das > > > > > > <biju.das.jz@xxxxxxxxxxxxxx> wrote: > > > > > > > > > On RZ/G2L SoCs switching from DMA to interrupt mode, > > > > > > > > > causes timeout issue as we are not getting Rx interrupt > > > > > > > > > even though SPRF bit is set in the status register. > > > > > > > > > > > > > > > > > > But there is no issue if we don't switch between interrupt > > > > > > > > > to DMA mode or vice versa. > > > > > > > > > > > > > > > > > > Performance comparison between interrupt and DMA mode on > > > > > > > > > RZ/Five SMARC platform connected to a display module shows > > > > > > > > > that performance and CPU utilization is much better with > > > > > > > > > DMA mode compared to interrupt mode > > > > > > > > > (1->65 fps) and (98->8%). > > > > > > > > > > > > > > > > > > This patch introduces a variable force_dma to avoid > > > > > > > > > switching between DMA to interrupt mode for RZ platforms. > > > > > > > > Why do you need a variable for that, if DMA is availble (you were > > > > able to allocate channels) then use DMA, otherwise fall back to PIO.. > > > > > > I was using DMA. We are not getting rspi interrupts after the DMA to > > > PIO switch because of [1]. ie, we are not clearing DMAR in DMA driver > > > and interrupt requests to the interrupt controller are masked. > > > > > > [1] > > > > > > > > > > > Or anything missing from context which I am not aware of? > > > > > > After this discussion, I have posted [1] and [2] to fix this issue. > > > > > > [2] > > > > Thanks for the explanation Biju. But why do we need .force_dma flag? > > It is not required. This patch is not valid anymore. okay, that sounds about right! > Initially I met with an issue(PIO fallback does not work). So posted this patch to make all transfer DMA by using .force_dma flag. > > Then Mark suggested that we should find the root cause. After that, Geert mentioned > we are not clearing DMARS, that is the reason for interrupt miss. > > During DMA prepare, we set RSPI DMARS and signal is set for DMA transfer request signal > and it masks rspi interrupts. When we do PIO mode, still DMARS is set, and we won't get rspi > interrupt. > > The new patches which I posted[1] and [2] clears DMARS in dmaengine_synchronize() in dma callback > after synchronizing with wait_event and PIO fallback works as expected. > > [1] https://patchwork.kernel.org/project/linux-renesas-soc/patch/20220719150000.383722-1-biju.das.jz@xxxxxxxxxxxxxx/ > [2] https://patchwork.kernel.org/project/linux-renesas-soc/patch/20220719150000.383722-2-biju.das.jz@xxxxxxxxxxxxxx/ > > Cheers, > Biju -- ~Vinod
