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? 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. AFAIUI max_dma_len is used when splitting up the buffer for the sg table in spi_map_buf(). Noralf. > Please, fix. > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
