linux-kernel - Re: [PATCH v2] spi: omap2-mcspi: disable other channels CHCONF_FORCE in prepare

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Date:	Fri, 9 Oct 2015 10:26:22 -0500
From:	Michael Welling <mwelling@...e.org>
To:	Neil Armstrong <narmstrong@...libre.com>
Cc:	Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
	linux-kernel@...r.kernel.org, Fionn Cleary <clearyf@....ie>,
	Wolfram Sang <wsa@...-dreams.de>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	Sebastian Reichel <sre@...nel.org>
Subject: Re: [PATCH v2] spi: omap2-mcspi: disable other channels CHCONF_FORCE
 in prepare_message

On Fri, Oct 09, 2015 at 03:47:41PM +0200, Neil Armstrong wrote:
> Since the "Switch driver to use transfer_one" change, the cs_change
> behavior has changed and a channel chip select can still be
> asserted when changing channel from a previous last transfer in a
> message having the cs_change attribute.
> 
> Since there is no sense having multiple chip select being asserted at the
> same time, disable all the remaining forced chip selects in a the
> prepare_message called right before a spi_transfer_one_message call.
> It ignores the current channel configuration in order to keep the
> possibility to leave the chip select asserted between messages.
> 
> It fixes this bug on a DM8168 SoC ES2.1 Soc and an OMAP4 ES2.1 SoC.
> It was hanging all the other channels transfers when a CHCONF_FORCE
> is present on the wrong channel.
> 
> Fixes: b28cb9414db9 ("spi: omap2-mcspi: Switch driver to use transfer_one")
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---
>  drivers/spi/spi-omap2-mcspi.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> Test code can be found on :
> http://pastebin.com/0SrqbGP7
> 
> Before patch :
> # ./test_spi
> cs_change_command() start
> spidev1.3 ioctl success
> no_dma_command() start
> [   59.790069] spidev spi1.1: TXS timed out
> spidev1.1 ioctl success
> cs_change_command() start
> [   60.798736] spidev spi1.3: RXS timed out
> spidev1.3 ioctl success
> no_dma_command() start
> [   61.802032] spidev spi1.1: TXS timed out
> spidev1.1 ioctl success
> cs_change_command() start
> [   62.807525] spidev spi1.3: RXS timed out
> spidev1.3 ioctl success
> no_dma_command() start
> [   63.812042] spidev spi1.1: TXS timed out
> spidev1.1 ioctl success
> ...
> 
> After Patch :
> # ./test_spi
> cs_change_command() start
> spidev1.3 ioctl success
> no_dma_command() start
> spidev1.1 ioctl success
> cs_change_command() start
> spidev1.3 ioctl success
> no_dma_command() start
> spidev1.1 ioctl success
> cs_change_command() start
> spidev1.3 ioctl success
> ...
> 
> v2: uses msg to leave asserted chip select for the current channel
> 
> This is a patch RFC following the bug report :
> 'McSPI hangs with cs_change after "Switch driver to use transfer_one" change'
> http://permalink.gmane.org/gmane.linux.kernel/2056841
> 
> diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
> index 3d09e0b..1f8903d 100644
> --- a/drivers/spi/spi-omap2-mcspi.c
> +++ b/drivers/spi/spi-omap2-mcspi.c
> @@ -1217,6 +1217,33 @@ out:
>  	return status;
>  }
> 
> +static int omap2_mcspi_prepare_message(struct spi_master *master,
> +				       struct spi_message *msg)
> +{
> +	struct omap2_mcspi	*mcspi = spi_master_get_devdata(master);
> +	struct omap2_mcspi_regs	*ctx = &mcspi->ctx;
> +	struct omap2_mcspi_cs	*cs;
> +

Do we need the pm_runtime_get_sync code here?
See previous commit.

> +	/* Only a single channel can have the FORCE bit enabled
> +	 * in its chconf0 register.
> +	 * Scan all channels and disable them except the current one.
> +	 * A FORCE can remain from a last transfer having cs_change enabled
> +	 */
> +	list_for_each_entry(cs, &ctx->cs, node) {
> +		if (msg->spi->controller_state == cs)
> +			continue;
> +
> +		if ((cs->chconf0 & OMAP2_MCSPI_CHCONF_FORCE)) {
> +			cs->chconf0 &= ~OMAP2_MCSPI_CHCONF_FORCE;
> +			writel_relaxed(cs->chconf0,
> +					cs->base + OMAP2_MCSPI_CHCONF0);
> +			readl_relaxed(cs->base + OMAP2_MCSPI_CHCONF0);
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static int omap2_mcspi_transfer_one(struct spi_master *master,
>  		struct spi_device *spi, struct spi_transfer *t)
>  {
> @@ -1344,6 +1371,7 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
>  	master->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 32);
>  	master->setup = omap2_mcspi_setup;
>  	master->auto_runtime_pm = true;
> +	master->prepare_message = omap2_mcspi_prepare_message;
>  	master->transfer_one = omap2_mcspi_transfer_one;
>  	master->set_cs = omap2_mcspi_set_cs;
>  	master->cleanup = omap2_mcspi_cleanup;
> -- 
> 1.9.1
> 
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