On Tue, Oct 15, 2019 at 06:05:16PM +0200, Daniel Vetter wrote: > On Tue, Oct 15, 2019 at 5:59 PM Andy Shevchenko > <andriy.shevchenko@xxxxxxxxx> wrote: > > On Tue, Oct 15, 2019 at 05:41:53PM +0200, Noralf Trønnes wrote: > > > Den 15.10.2019 16.32, skrev Andy Shevchenko: > > > > On Fri, Jul 19, 2019 at 05:59:10PM +0200, Noralf Trønnes wrote: > > > >> spi-bcm2835 can handle >64kB buffers now so there is no need to check > > > >> ->max_dma_len. The tinydrm_spi_max_transfer_size() max_len argument is > > > >> not used by any callers, so not needed. > > > >> > > > >> Then we have the spi_max module parameter. It was added because > > > >> staging/fbtft has support for it and there was a report that someone used > > > >> it to set a small buffer size to avoid popping on a USB soundcard on a > > > >> Raspberry Pi. In hindsight it shouldn't have been added, I should have > > > >> waited for it to become a problem first. I don't know it anyone is > > > >> actually using it, but since tinydrm_spi_transfer() is being moved to > > > >> mipi-dbi, I'm taking the opportunity to remove it. I'll add it back to > > > >> mipi-dbi if someone complains. > > > >> > > > >> With that out of the way, spi_max_transfer_size() can be used instead. > > > >> > > > >> The chosen 16kB buffer size for Type C Option 1 (9-bit) interface is > > > >> somewhat arbitrary, but a bigger buffer will have a miniscule impact on > > > >> transfer speed, so it's probably fine. > > > > > > > > This breaks the SPI PXA2xx case I'm using. The world is not a Pi:e. > > > > > > > > [ 388.445752] mi0283qt spi-PRP0001:01: DMA disabled for transfer length 153600 greater than 65536 > > > > [ 388.634437] mi0283qt spi-PRP0001:01: DMA disabled for transfer length 153600 greater than 65536 > > > > [ 388.822933] mi0283qt spi-PRP0001:01: DMA disabled for transfer length 153600 greater than 65536 > > > > > > > > The crucial thing is to check the transfer size against maximum DMA length > > > > of the master. > > > > > > > > > > Isn't this a spi controller driver problem? > > > > It doesn't matter. This patch made a regression. Before it worked, > > now it doesn't. > > Yes this is clear. > > > > spi_max_transfer_size() tells the client what the maximum transfer > > > length is. The controller driver can use ctlr->max_transfer_size if it > > > has restrictions. > > > > It might be a problem of the SPI core. > > > > > AFAIUI max_dma_len is used when splitting up the buffer for the sg table > > > in spi_map_buf(). > > > > > > Please, fix. > > > > Should I send the revert? > > Can we please not roll in with the cavalry before everyone had a > chance to wake up and look at this properly? It's less than 1h since > your initial bug report. It was a simple question to the 1st level maintainer of the subsystem, who already read the report and answered to it. > Also, you _do_ have a test patch in your inbox ... Yes, thanks for it, I'm going to test right now. -- With Best Regards, Andy Shevchenko _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
