Bug #7634
Updated by Gordon Ross over 5 years ago
Some i915 hardware cannot handle DMA below 0xff000, so the driver would normally use DMA attributes like this:
(Note the dma_attr_lo field)
<pre>
static ddi_dma_attr_t ppgt_dma_attr = {
DMA_ATTR_V0,
0xff000U, /* dma_attr_addr_lo */
0xffffffffU, /* dma_attr_addr_hi */
0xffffffffU, /* dma_attr_count_max */
4096, /* dma_attr_align */
0x1fffU, /* dma_attr_burstsizes */
1, /* dma_attr_minxfer */
0xffffffffU, /* dma_attr_maxxfer */
0xffffffffU, /* dma_attr_seg */
1, /* dma_attr_sgllen, variable */
4, /* dma_attr_granular */
DDI_DMA_FLAGERR, /* dma_attr_flags */
};
</pre>
Unfortunately, ddi_dma_alloc fails when dma_attr_addr_lo > 0.
Better DRM support on i915 needs that fixed.
When this is fixed, we'll undo the (temporary) fix shown in:
#7626 PPGTT setup problem