linux-kernel - [PATCH][linux-next] soc: fsl: dpio: Unsigned compared against 0 in qbman_swp_set_irq

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Message-Id: <20211018160541.13512-1-tim.gardner@canonical.com>
Date:   Mon, 18 Oct 2021 10:05:41 -0600
From:   Tim Gardner <tim.gardner@...onical.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     tim.gardner@...onical.com, Roy Pledge <Roy.Pledge@....com>,
        Li Yang <leoyang.li@....com>, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH][linux-next] soc: fsl: dpio: Unsigned compared against 0 in qbman_swp_set_irq_coalescing()

Coverity complains of unsigned compare against 0. There are 2 cases in
this function:

1821        itp = (irq_holdoff * 1000) / p->desc->qman_256_cycles_per_ns;

CID 121131 (#1 of 1): Unsigned compared against 0 (NO_EFFECT)
unsigned_compare: This less-than-zero comparison of an unsigned value is never true. itp < 0U.
1822        if (itp < 0 || itp > 4096) {
1823                max_holdoff = (p->desc->qman_256_cycles_per_ns * 4096) / 1000;
1824                pr_err("irq_holdoff must be between 0..%dus\n", max_holdoff);
1825                return -EINVAL;
1826        }
1827
    	unsigned_compare: This less-than-zero comparison of an unsigned value is never true. irq_threshold < 0U.
1828        if (irq_threshold >= p->dqrr.dqrr_size || irq_threshold < 0) {
1829                pr_err("irq_threshold must be between 0..%d\n",
1830                       p->dqrr.dqrr_size - 1);
1831                return -EINVAL;
1832        }

Fix this by checking for 0. Also fix a minor comment typo.

Fixes ed1d2143fee53755ec601eb4d48a337a93933f71 ("soc: fsl: dpio: add support for
irq coalescing per software portal")

Cc: Roy Pledge <Roy.Pledge@....com>
Cc: Li Yang <leoyang.li@....com>
Cc: linux-kernel@...r.kernel.org
Cc: linuxppc-dev@...ts.ozlabs.org
Cc: linux-arm-kernel@...ts.infradead.org
Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
---

I'm not 100% sure this is the right way to fix the warning, but according to the
pr_err() comments these values should never be 0.

---
 drivers/soc/fsl/dpio/qbman-portal.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/soc/fsl/dpio/qbman-portal.c b/drivers/soc/fsl/dpio/qbman-portal.c
index d3c58df6240d..b768a14bb271 100644
--- a/drivers/soc/fsl/dpio/qbman-portal.c
+++ b/drivers/soc/fsl/dpio/qbman-portal.c
@@ -1816,16 +1816,16 @@ int qbman_swp_set_irq_coalescing(struct qbman_swp *p, u32 irq_threshold,
 	u32 itp, max_holdoff;
 
 	/* Convert irq_holdoff value from usecs to 256 QBMAN clock cycles
-	 * increments. This depends to the QBMAN internal frequency.
+	 * increments. This depends on the QBMAN internal frequency.
 	 */
 	itp = (irq_holdoff * 1000) / p->desc->qman_256_cycles_per_ns;
-	if (itp < 0 || itp > 4096) {
+	if (!itp || itp > 4096) {
 		max_holdoff = (p->desc->qman_256_cycles_per_ns * 4096) / 1000;
 		pr_err("irq_holdoff must be between 0..%dus\n", max_holdoff);
 		return -EINVAL;
 	}
 
-	if (irq_threshold >= p->dqrr.dqrr_size || irq_threshold < 0) {
+	if (irq_threshold >= p->dqrr.dqrr_size || !irq_threshold) {
 		pr_err("irq_threshold must be between 0..%d\n",
 		       p->dqrr.dqrr_size - 1);
 		return -EINVAL;
-- 
2.33.1