On Tue, 27 Jun 2017, Ondrej Zary wrote: > On Tuesday 27 June 2017 14:42:29 Finn Thain wrote: > > > > ... it triggers sometimes: the value is 1 instead of 0. As we use > > > only 16-bit writes, I don't see how the value could ever be odd. > > > Looks like a bug in the chip. The index register corrupts during the > > > transfer, not after IRQ or timeout. The same check at beginning of > > > pwrite() did not trigger. > > > > Are you reading this register at the right moment? Have you tried > > waiting for it to reach zero, as in, > > > > if (NCR5380_poll_politely(hostdata, 13, 0xff, 0, HZ / 64) < 0) > > /* printk, reset etc */; > > I have not but will try (expecting that it will not change by itself). > Now that I know that it is the byte at the beginning of the block that went missing, I agree that there's no point waiting for the byte count to change. I've included a patch with your 512 B limit in v4. Thanks. > > Even if this is a reliable way to detect a short transfer, it would be > > nice to know the root cause. But I'm being unrealistic: the DTC436 > > vendor never responded to my requests for technical documentation. > > According to the data corruption observed, it's not a short transfer. > The corruption is always the same: one byte missing at the beginning of > a 128 B block. It happens only with slow Quantum LPS 240 drive, not with > faster IBM DORS-32160. > --
