linux-kernel - Re: [PATCH] spi: fsl-espi: Only process interrupts for expected events

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Message-ID: <ecedc71d-100a-7d7a-ff7f-ef1a3086dd74@alliedtelesis.co.nz>
Date:   Sun, 13 Sep 2020 22:03:45 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     "broonie@...nel.org" <broonie@...nel.org>,
        "npiggin@...il.com" <npiggin@...il.com>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "Joakim Tjernlund" <Joakim.Tjernlund@...inera.com>
CC:     "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] spi: fsl-espi: Only process interrupts for expected
 events

Hi All,

On 4/09/20 12:28 pm, Chris Packham wrote:
> The SPIE register contains counts for the TX FIFO so any time the irq
> handler was invoked we would attempt to process the RX/TX fifos. Use the
> SPIM value to mask the events so that we only process interrupts that
> were expected.
>
> This was a latent issue exposed by commit 3282a3da25bd ("powerpc/64:
> Implement soft interrupt replay in C").
>
> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
> Cc: stable@...r.kernel.org
> ---
ping?
>
> Notes:
>      I've tested this on a T2080RDB and a custom board using the T2081 SoC. With
>      this change I don't see any spurious instances of the "Transfer done but
>      SPIE_DON isn't set!" or "Transfer done but rx/tx fifo's aren't empty!" messages
>      and the updates to spi flash are successful.
>      
>      I think this should go into the stable trees that contain 3282a3da25bd but I
>      haven't added a Fixes: tag because I think 3282a3da25bd exposed the issue as
>      opposed to causing it.
>
>   drivers/spi/spi-fsl-espi.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/spi/spi-fsl-espi.c b/drivers/spi/spi-fsl-espi.c
> index 7e7c92cafdbb..cb120b68c0e2 100644
> --- a/drivers/spi/spi-fsl-espi.c
> +++ b/drivers/spi/spi-fsl-espi.c
> @@ -574,13 +574,14 @@ static void fsl_espi_cpu_irq(struct fsl_espi *espi, u32 events)
>   static irqreturn_t fsl_espi_irq(s32 irq, void *context_data)
>   {
>   	struct fsl_espi *espi = context_data;
> -	u32 events;
> +	u32 events, mask;
>   
>   	spin_lock(&espi->lock);
>   
>   	/* Get interrupt events(tx/rx) */
>   	events = fsl_espi_read_reg(espi, ESPI_SPIE);
> -	if (!events) {
> +	mask = fsl_espi_read_reg(espi, ESPI_SPIM);
> +	if (!(events & mask)) {
>   		spin_unlock(&espi->lock);
>   		return IRQ_NONE;
>   	}