linux-kernel - Re: [PATCH 1/1] i2c: ocores: fix polling mode workaround on FU540-C000 SoC

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Message-ID: <87imbm4639.fsf@dell.be.48ers.dk>
Date:   Wed, 07 Oct 2020 13:40:26 +0200
From:   Peter Korsgaard <peter@...sgaard.com>
To:     Sagar Shrikant Kadam <sagar.kadam@...ive.com>
Cc:     linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-i2c@...r.kernel.org, andrew@...n.ch,
        paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu
Subject: Re: [PATCH 1/1] i2c: ocores: fix polling mode workaround on FU540-C000 SoC

>>>>> "Sagar" == Sagar Shrikant Kadam <sagar.kadam@...ive.com> writes:

 > The FU540-C000 has a broken IRQ and support was added earlier
 > so that it will operate in polling mode, but seems to work only
 > in case interrupts property is missing from the i2c0 dt-node.
 > This should not be the case and the driver should handle polling
 > mode with the interrupt property present in i2c0 node of the
 > device tree.
 > So check if it's the FU540-C000 soc and enable polling mode master
 > xfers, as the IRQ for this chip is broken.

 > Fixes commit c45d4ba86731 ("i2c: ocores: add polling mode workaround
 > for Sifive FU540-C000 SoC")

 > Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@...ive.com>
 > ---
 >  drivers/i2c/busses/i2c-ocores.c | 22 +++++++++++++---------
 >  1 file changed, 13 insertions(+), 9 deletions(-)

 > diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
 > index f5fc75b..4405244 100644
 > --- a/drivers/i2c/busses/i2c-ocores.c
 > +++ b/drivers/i2c/busses/i2c-ocores.c
 > @@ -686,17 +686,21 @@ static int ocores_i2c_probe(struct platform_device *pdev)
 
 >  	init_waitqueue_head(&i2c->wait);
 
 > +	/*
 > +	 * Set OCORES_FLAG_BROKEN_IRQ to enable workaround for
 > +	 * FU540-C000 SoC in polling mode.
 > +	 * Since the SoC does have interrupt it's dt has the interrupt
 > +	 * defined but it should be bypassed in driver as this SoC has
 > +	 * a broken IRQ, hence update the master_xfer to use polling
 > +	 * transfers.
 > +	 */
 > +	match = of_match_node(ocores_i2c_match, pdev->dev.of_node);
 > +	if (match && (long)match->data == TYPE_SIFIVE_REV0)
 > +		i2c->flags |= OCORES_FLAG_BROKEN_IRQ;
 > +
 >  	irq = platform_get_irq(pdev, 0);
 > -	if (irq == -ENXIO) {
 > +	if (i2c->flags == OCORES_FLAG_BROKEN_IRQ || irq == -ENXIO) {

NIT: flags is a bitmask, so i2c->flags & OCORES_FLAG_BROKEN_IRQ would be
better, even if there currently doesn't exist any other flags.

TYPE_SIFIVE_REV0 is also set for two compatibles:

        {
                .compatible = "sifive,fu540-c000-i2c",
                .data = (void *)TYPE_SIFIVE_REV0,
        },
        {
                .compatible = "sifive,i2c0",
                .data = (void *)TYPE_SIFIVE_REV0,
        },

Are both affected by this issue? if not, we will need to extend the code
to handle them differently.

Other than that, it looks OK to me.

-- 
Bye, Peter Korsgaard