From: Guenter Roeck <linux@roeck-us.net>
To: Bin Meng <bmeng.cn@gmail.com>
Cc: "Peter Maydell" <peter.maydell@linaro.org>,
"Cheng, Xuzhou" <Xuzhou.Cheng@windriver.com>,
"Alistair Francis" <alistair@alistair23.me>,
"QEMU Developers" <qemu-devel@nongnu.org>,
"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
qemu-arm <qemu-arm@nongnu.org>,
"Jean-Christophe Dubois" <jcd@tribudubois.net>
Subject: Re: [PATCH] hw/ssi: imx_spi: Improve chip select handling
Date: Fri, 1 Oct 2021 06:04:23 -0700 [thread overview]
Message-ID: <20211001130423.GA549865@roeck-us.net> (raw)
In-Reply-To: <CAEUhbmVVjXKUxa95+GPPZSU5=isgTs7EMnN7gxgYn9Lkg+a0Xg@mail.gmail.com>
On Sun, Sep 26, 2021 at 10:49:53AM +0800, Bin Meng wrote:
> On Sat, Sep 18, 2021 at 12:19 PM Guenter Roeck <linux@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.
>
Thanks a lot for tracking this down!
Guenter
next prev parent reply other threads:[~2021-10-01 13:07 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-08 1:34 [PATCH] hw/ssi: imx_spi: Improve chip select handling Guenter Roeck
2021-09-02 15:58 ` Peter Maydell
2021-09-02 16:09 ` Guenter Roeck
2021-09-02 19:29 ` Peter Maydell
2021-09-04 17:13 ` Guenter Roeck
2021-09-04 23:06 ` Bin Meng
2021-09-04 23:19 ` Philippe Mathieu-Daudé
2021-09-05 2:08 ` Guenter Roeck
2021-09-08 6:29 ` Bin Meng
2021-09-08 6:31 ` Bin Meng
2021-09-08 9:05 ` Cheng, Xuzhou
2021-09-08 16:52 ` Guenter Roeck
2021-09-16 10:21 ` Cheng, Xuzhou
2021-09-16 14:21 ` Guenter Roeck
2021-09-18 3:09 ` Cheng, Xuzhou
2021-09-18 4:19 ` Guenter Roeck
2021-09-26 2:49 ` Bin Meng
2021-10-01 13:04 ` Guenter Roeck [this message]
2021-09-05 2:05 ` Guenter Roeck
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