James Hogan wrote: > On 09/22/2011 11:01 AM, Jaehoon Chung wrote: >> This patch modified the DMA threshold. >> >> I didn't know exactly why need this threshold. >> But if this value is 16, we didn't read SCR register for SD card. >> Because in mmc_app_send_scr this values are used data.blocks=1 and data.blksz=8. >> (data.blocks * data.blksz = 8...so return -EINVAL) > > The idea is that for a small transaction the time to set up the DMA is > probably not worth the effort, therefore it does it using PIO mode (see > dw_mci_submit_data, if dw_mci_submit_data_dma fails, it sets itself up > for pio mode instead). Is there some reason that threshold is set 16? > > So if it's using PIO mode and the SCR cannot be read, then PIO mode is > broken. What's the value of the register HCON? dw_mci_probe reads it and > decides which pio push and pull function to use based on the host data > width. I've only tested one of them as we only have one configuration of > hardware available, but you may have a different one. i used push/pull_data_32. What do you doubt this problem? Best regards, Jaehon Chung -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
