On Sat, Sep 18, 2021 at 12:19 PM Guenter Roeck <li...@roeck-us.net> wrote: > > On 9/17/21 8:09 PM, Cheng, Xuzhou wrote: > >>> I got some free time in the past days to investigate this issue. Guenter > >>> is right, the Linux imx-spi driver does not work on QEMU. > >>> > >>> The reason is that the state of m25p80 machine loops in > >>> STATE_READING_DATA state after receiving RDSR command, the new command is > >>> ignored. Before sending a new command, the CS line should be pulled to > >>> high, this make the state of m25p80 back to IDLE. > >>> > >>> I have same point with Guenter, it's that set CS to 1 when burst is zero. > >>> But i don't think it is necessary to set CS to 0 in > >>> imx_spi_flush_txfifo(). I will send a new patch to fix this issue. > >>> > >> > >> Thanks a lot for looking into this. If you have a better solution than > >> mine, by all means, please go for it. As I mentioned in my patch, I didn't > >> really like it, but I was unable to find a better solution. > > I am doing some experiment to verify that the new patch is reasonable, so > > the new patch will be delayed few days. > > > > No problem. Note that I'll be traveling for the next 2-3 weeks, and I won't > be able > to test any patches during that time. >
I have some updates to share, as I have been working with Xuzhou internally on this issue for the past days: Current mods using BURST_LEN to determine the timing to pull up the CS line in the SPI controller codes is a workaround. Hardware does not do this. To understand what real hardware behavior is, Xuzhou used an oscilloscope to verify our guess. It turns out the root cause is elsewhere, and a proper fix will be sent out soon. Regards, Bin
