On 11/05/2015 11:34 PM, Bin Liu wrote:
Here are a few changes in musb_h_tx_flush_fifo(). - Refering to 2ccc6d30a (usb: musb: fix bit mask for CSR in musb_h_tx_flush_fifo()), the datasheet says that MUSB_TXCSR_FLUSHFIFO is only valid when MUSB_TXCSR_TXPKTRDY is set as well. It means MUSB_TXCSR_TXPKTRDY should be checked, not set.Hum, my copy of the MUSBHDRC programmer's guide says about TXCSR.FlushFIFO in host mode: << The CPU writes a 1 to this bit to flush the latest packet from the endpoint Tx FIFO. The FIFO pointer is reset, the TxPktRdy bit (below) is cleared and an interrupt is generated. May be set simultaneously with TxPktRdy to abort the packet that is currently being loaded into the FIFO. Note: FlushFIFO should only be used when TxPktRdy is set. At other times, it may cause data to be corrupted. Also note that, if the FIFO is double-buffered, FlushFIFO may need to be set twice to completely clear the FIFO. >>So how to interpret this message? FLUSHFIFO and TXPKTRDY should be set at the same time? If so, I will drop this change in V3.Yes, I think it's rather clear in this respect.In either case, musb is unable to flush the tx fifo in urb dequque for device disconnect, but harmless, so the next two changes are important to give better user experience.Hm, looks like some errata... and hiding this from users while there's no workaround doesn't seem a good policy.Well, based on the programmer's guide, the driver should set the flushFIFO bit, and wait for the interrupt.
That's oversimplified, consider the double-buffered FIFO. ;-)
However, the driver does 1000-times retry loop to probe the FIFONOTEMPTY bit. This is there in the very first version of the driver back in 2008. So I would think musb just behaves like that, rather than an errata. Also the WARN() was not there in the early version of the driver.
Yes, but added shortly after, in 2008.
Please guide what we will do with this patch? Should I send V3 with the first change removed, or just drop this patch completely?
I'll let Felipe decide, it's his domain.
Thanks, -Bin.
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