drm/tinydrm: Remove tinydrm_spi_max_transfer_size()

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.

Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190719155916.62465-6-noralf@tronnes.org

1 files changed, 0 insertions, 1 deletions

diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
index dca75de3a359..10b35375a009 100644
--- a/include/drm/tinydrm/tinydrm-helpers.h
+++ b/include/drm/tinydrm/tinydrm-helpers.h
@@ -41,7 +41,6 @@ int tinydrm_display_pipe_init(struct drm_device *drm,
 			      const struct drm_display_mode *mode,
 			      unsigned int rotation);
 
-size_t tinydrm_spi_max_transfer_size(struct spi_device *spi, size_t max_len);
 int tinydrm_spi_transfer(struct spi_device *spi, u32 speed_hz,
 			 struct spi_transfer *header, u8 bpw, const void *buf,
 			 size_t len);