On Wed, Jan 22, 2014 at 04:00:23PM +0100, Ulf Hansson wrote: > In case of a read operation both MCI_CMDRESPEND and MCI_DATAEND can be > set in the status register when entering the interrupt handler. This is > due to that the card start sending data before the host has > acknowledged the command response. > > To resolve the issue for this scenario, we must start by handling the > CMD irq instead of the DATA irq. The reason is beacuse the completion > of the DATA irq will not respect the current command and then causing > it to be garbled. And that's because the driver isn't written to be able to handle a command being issued concurrently with a data transfer, because it only has one place to store the current command. Consider what happens in this case: - Command issued to start a transfer. - Command completes, data transfer starts. - New command comes along to be issued, and is in progress - Data transfer finishes, we now issue the stop command to halt the transfer - We overwrite the new command with the stop command All hell breaks loose. No, this isn't a fix I want to see until the driver can properly handle concurrent commands. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". -- 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
