HOST1X_CHANNEL_DMASTART
host1x_ch_writel(ch, lower_32_bits(start), HOST1X_CHANNEL_DMASTART);
host1x_ch_writel(ch, lower_32_bits(start), HOST1X_CHANNEL_DMASTART);
dmastart = host1x_ch_readl(ch, HOST1X_CHANNEL_DMASTART);
dmastart |= host1x_ch_readl(ch, HOST1X_CHANNEL_DMASTART);