Hi Support Team,
We have successfully enabled the st7789 sitronix SPI based LCD using the framebuffer (driver/staging/fbtft) driver. Now, we are trying to enable the same driver using GPU/DRM (drivers/gpu/drm/tinydrm/) drivers.
We have ported the driver with DRM/GPU subsystem path. While kernel probing the driver, we got the SPI-DMA related errors. Errors are as shown below:
root@linaro-alip:~# dmesg | grep -i st77
[ 1.362935] ei: func:st7789v_probe line:164
[ 1.368970] st7789v spi0.0: Failed to set dma mask -5
[ 1.373023] st7789v: probe of spi0.0 failed with error -5
We have debugged the file : drivers/gpu/drm/tinydrm/mipi-dbi.c and the function mipi_dbi_spi_init.
/*
- Even though it’s not the SPI device that does DMA (the master does),
- the dma mask is necessary for the dma_alloc_wc() in
- drm_gem_cma_create(). The dma_addr returned will be a physical
- adddress which might be different from the bus address, but this is
- not a problem since the address will not be used.
- The virtual address is used in the transfer and the SPI core
- re-maps it on the SPI master device using the DMA streaming API
- (spi_map_buf()).
*/
if (!dev->coherent_dma_mask) {
ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(32));
if (ret) {
dev_warn(dev, “Failed to set dma mask %d\n”, ret);
return ret;
}
}
If we commented above code from the file, the DRI node is created and gives below error:
st7789v spi0.0: failed to allocate a buffer with size 131072
root@linaro-alip:~# cat /sys/kernel/debug/dri/0/name
st7789v dev=spi0.0 unique=spi0.0
Can you please help us, what will be the missing parameter?
Thanks,
Arjun
