Re: Boot failure with 5.4-rc5, bisected to 0f0581b24bd0 ("spi: fsl: Convert to use CS GPIO descriptors")

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Fri, Nov 8, 2019 at 1:33 PM Christophe Leroy <christophe.leroy@xxxxxx> wrote:

> [    3.227053] NIP [c0249054] gen_pool_free_owner+0xfc/0x100
> [    3.232377] LR [c0249054] gen_pool_free_owner+0xfc/0x100
> [    3.237588] Call Trace:
> [    3.240037] [c60e1d08] [c0249054] gen_pool_free_owner+0xfc/0x100
> (unreliable)
> [    3.247113] [c60e1d38] [c0299020] cpm_muram_free+0x84/0xf4
> [    3.252517] [c60e1d58] [c030e7a4] fsl_spi_cpm_free+0x94/0x100
> [    3.258198] [c60e1d68] [c030f2d4] of_fsl_spi_probe+0x260/0x3a0

Since fsl_spi_cpm_free() is called from of_fsl_spi_probe() and doesn't
even exist on the errorpath of this function I suppose it is some kind
inlining of_fsl_spi_probe() which goes on the errorpath and
crashes there. I suspect EPROBE_DEFER (-517) to be behind this
but it is just a guess.

What happens if you add this:

diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c
index 4b80ace1d137..a26b5e542006 100644
--- a/drivers/spi/spi-fsl-spi.c
+++ b/drivers/spi/spi-fsl-spi.c
@@ -678,6 +678,7 @@ static struct spi_master * fsl_spi_probe(struct device *dev,
        return master;

 err_probe:
+       dev_info(dev, "bail out with error code %d\n", ret);
        fsl_spi_cpm_free(mpc8xxx_spi);
 err_cpm_init:
        spi_master_put(master);

I am assuming that the errorpath inside spi-fsl-cpm.c is crashing,
as cpm_muram_free() is called under the wrong conditions,
or simply not really working.

So fixing the errorpath is a separate problem in itself.

By just looking at the code and not understanding any more than
that the error path on fsl_spi_cpm_free() should probably
equal that of fsl_spi_cpm_init() I guess maybe this could
fix it, could you test?

diff --git a/drivers/spi/spi-fsl-cpm.c b/drivers/spi/spi-fsl-cpm.c
index 858f0544289e..54ad0ac121e5 100644
--- a/drivers/spi/spi-fsl-cpm.c
+++ b/drivers/spi/spi-fsl-cpm.c
@@ -392,7 +392,8 @@ void fsl_spi_cpm_free(struct mpc8xxx_spi *mspi)
        dma_unmap_single(dev, mspi->dma_dummy_rx, SPI_MRBLR, DMA_FROM_DEVICE);
        dma_unmap_single(dev, mspi->dma_dummy_tx, PAGE_SIZE, DMA_TO_DEVICE);
        cpm_muram_free(cpm_muram_offset(mspi->tx_bd));
-       cpm_muram_free(cpm_muram_offset(mspi->pram));
+       if (!(mspi->flags & SPI_CPM1))
+               cpm_muram_free(cpm_muram_offset(mspi->pram));
        fsl_spi_free_dummy_rx();
 }
 EXPORT_SYMBOL_GPL(fsl_spi_cpm_free);

> Reverting 0f0581b24bd0 ("spi: fsl: Convert to use CS GPIO descriptors")
> solves the issue.

I hope we can fix the errorpath so we can see what the real problem
is with this patch.

> Renaming the gpios item to cs-gpios in the devicetree fixes the crash on
> boot but the following warning appears during boot and SPI doesn't work
> (can't read board temperature on LM74 chip):

That's annoying. I hope we can get the code to work though,
let's hammer on it a bit and see if we can fix it!

Yours,
Linus Walleij