HOST1X_CHANNEL_DMASTART_HI
host1x_ch_writel(ch, upper_32_bits(start), HOST1X_CHANNEL_DMASTART_HI);
host1x_ch_writel(ch, upper_32_bits(start), HOST1X_CHANNEL_DMASTART_HI);
dmastart = host1x_ch_readl(ch, HOST1X_CHANNEL_DMASTART_HI);