linux-kernel - Re: [PATCH RESEND v4 0/6] dmaengine: dw: Fix src/dst addr width misconfig

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Message-ID: <635sp3moq2csr34yeut5tedmehpr5brejed5hlrj25u63hg5tw@6v36r2emdt7d>
Date: Mon, 16 Sep 2024 00:34:19 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Ferry Toth <ftoth@...londelft.nl>, Viresh Kumar <vireshk@...nel.org>, 
	Vinod Koul <vkoul@...nel.org>, Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, dmaengine@...r.kernel.org, 
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND v4 0/6] dmaengine: dw: Fix src/dst addr width
 misconfig

On Sun, Sep 15, 2024 at 02:43:19PM +0300, Andy Shevchenko wrote:
> On Sat, Sep 14, 2024 at 10:08 PM Serge Semin <fancer.lancer@...il.com> wrote:
> >
> > On Sat, Sep 14, 2024 at 10:06:16PM +0300, Serge Semin wrote:
> > > Hi Andy
> > >
> > > On Sat, Sep 14, 2024 at 09:50:48PM +0300, Andy Shevchenko wrote:
> > > > On Mon, Aug 05, 2024 at 03:25:35PM +0300, Serge Semin wrote:
> > > > > On Sat, Aug 03, 2024 at 09:29:54PM +0200, Andy Shevchenko wrote:
> > > > > > On Fri, Aug 2, 2024 at 9:51 AM Serge Semin <fancer.lancer@...il.com> wrote:
> > > > > > >
> > > > > > > The main goal of this series is to fix the data disappearance in case of
> > > > > > > the DW UART handled by the DW AHB DMA engine. The problem happens on a
> > > > > > > portion of the data received when the pre-initialized DEV_TO_MEM
> > > > > > > DMA-transfer is paused and then disabled. The data just hangs up in the
> > > > > > > DMA-engine FIFO and isn't flushed out to the memory on the DMA-channel
> > > > > > > suspension (see the second commit log for details). On a way to find the
> > > > > > > denoted problem fix it was discovered that the driver doesn't verify the
> > > > > > > peripheral device address width specified by a client driver, which in its
> > > > > > > turn if unsupported or undefined value passed may cause DMA-transfer being
> > > > > > > misconfigured. It's fixed in the first patch of the series.
> > > > > > >
> > > > > > > In addition to that three cleanup patches follow the fixes described above
> > > > > > > in order to make the DWC-engine configuration procedure more coherent.
> > > > > > > First one simplifies the CTL_LO register setup methods. Second and third
> > > > > > > patches simplify the max-burst calculation procedure and unify it with the
> > > > > > > rest of the verification methods. Please see the patches log for more
> > > > > > > details.
> > > > > > >
> > > > > > > Final patch is another cleanup which unifies the status variables naming
> > > > > > > in the driver.
> > > > > >
> > > > > > Acked-by: Andy Shevchenko <andy@...nel.org>
> > > > >
> > > > > Awesome! Thanks.
> > > >
> > > > Not really :-)
> > > > This series broke iDMA32 + SPI PXA2xx on Intel Merrifield.
> > >
> > > Damn. Sorry to hear that.(
> > >
> > > > I haven't
> > > > had time to investigate further, but rolling back all patches helps.
> > > >
> > > > +Cc: Ferry who might also test and maybe investigate as he reported the
> > > > issue to me initially.
> > >
> > > Ferry, could you please roll back the series patch-by-patch to find
> > > out the particular commit to blame?
> >
> > Plus to that it would be nice to have some log/info/details/etc about
> > what exactly is happening.
> 

> For me with patch
> 
> spitest -l -s1000000 -b128 /dev/spidev5.1
> SPI: [mode 0x20, bits_per_word 8, speed 1000000 Hz]
> [  164.525604] pxa2xx_spi_pci 0000:00:07.1: DMA slave config failed
> [  164.536105] pxa2xx_spi_pci 0000:00:07.1: failed to get DMA TX descriptor
> [  164.543213] spidev spi-SPT0001:00: SPI transfer failed: -16
> [  164.550140] spi_master spi5: failed to transfer one message from queue
> [  164.557126] spi_master spi5: noqueue transfer failed
> spitest: SPI transfer failed in iteration #0: Device or resource busy

Thanks for the log. As I suspected there is a safety-check failure,
which prevents the client driver from using the DMA-controller with
the specified transfer parameters.

It would be helpful if you find out which conditional statement in the
dwc_verify_p_buswidth(), dwc_verify_m_buswidth() methods cause the
failure. Also it would be useful to get the max_width, mem_width,
reg_width and reg_burst variables values.

-Serge(y)

> 
> Without
> 
> spitest -s 1000000 -b 128 -l /dev/spidev5.1
> SPI: [mode 0x20, bits_per_word 8, speed 1000000 Hz]
> SEND: [00000000] ff 97 d0 54 d5 69 85 6e ca e7 b3 e1 a1 e5 1a 9d
> ...
> RECV: [00000000] ff 97 d0 54 d5 69 85 6e ca e7 b3 e1 a1 e5 1a 9d
> ...
> 
> `spitest` is our internal tool, so what it does there is:
> 1) opens SPI device for speed 1MHz in loopback mode
> 2) generates 128 byte of random data
> 3) tries to send and receive them
> 4) compares
> 
> I believe the similar behaviour can be achieved with the one that is
> in the kernel tree.
> 
> -- 
> With Best Regards,
> Andy Shevchenko