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] https://patchwork.kernel.org/project/linux-renesas-soc/patch/20220719150000.383722-2-biju.das.jz@xxxxxxxxxxxxxx/ > > 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] https://patchwork.kernel.org/project/linux-renesas-soc/patch/20220719150000.383722-1-biju.das.jz@xxxxxxxxxxxxxx/ Cheers, Biju > > > > > > > > > > > > > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx> > > > > > > > > > > Thanks for your patch! > > > > > > > > > > > @@ -1196,6 +1197,7 @@ static const struct spi_ops rspi_rz_ops = { > > > > > > .flags = SPI_CONTROLLER_MUST_RX | > > > > > SPI_CONTROLLER_MUST_TX, > > > > > > .fifo_size = 8, /* 8 for TX, 32 for RX */ > > > > > > .num_hw_ss = 1, > > > > > > + .force_dma = true, > > > > > > }; > > > > > > > > > > Do you know if this is needed on RZ/A series, too? > > > > > > > > I guess it is needed?? I may be wrong. I got a link from Chris > > > > [1]. As per this still We haven't found a solution. May be the > > > > priority is changed for this activity and no one looked after this. > > > > > > > > [1] > > > > > > Daniel said he found the issue, i.e. the dmac driver never resetting > DMARS? > > > > Currently DMARS set during prepare and it never cleared. So I added > > device_synchronize callback in DMA driver to clear the DMARS. RSPI > > client driver after synchronizing DMA callback, calls > dmaengine_synchronize which clears DMARS. > > > > With this DMA to interrupt mode switching is working fine. > > > > Cheers, > > Biju > > > > -- > ~Vinod
