linux-kernel - [PATCH] phy: zynqmp: Allow variation in refclk rate

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Message-Id: <20230711194542.898230-1-sean.anderson@seco.com>
Date:   Tue, 11 Jul 2023 15:45:39 -0400
From:   Sean Anderson <sean.anderson@...o.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Michal Simek <michal.simek@....com>,
        linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org
Cc:     linux-arm-kernel@...ts.infradead.org,
        Sean Anderson <sean.anderson@...o.com>
Subject: [PATCH] phy: zynqmp: Allow variation in refclk rate

Due to limited available frequency ratios, the reference clock rate may
not be exactly the same as the required rate. Allow a small (100 ppm)
deviation.

Signed-off-by: Sean Anderson <sean.anderson@...o.com>
---

 drivers/phy/xilinx/phy-zynqmp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/phy/xilinx/phy-zynqmp.c b/drivers/phy/xilinx/phy-zynqmp.c
index b0c2045b886e..2559c6594cea 100644
--- a/drivers/phy/xilinx/phy-zynqmp.c
+++ b/drivers/phy/xilinx/phy-zynqmp.c
@@ -904,7 +904,10 @@ static int xpsgtr_get_ref_clocks(struct xpsgtr_dev *gtr_dev)
 		rate = clk_get_rate(clk);
 
 		for (i = 0 ; i < ARRAY_SIZE(ssc_lookup); i++) {
-			if (rate == ssc_lookup[i].refclk_rate) {
+			/* Allow an error of 100 ppm */
+			unsigned long error = ssc_lookup[i].refclk_rate / 10000;
+
+			if (abs(rate - ssc_lookup[i].refclk_rate) < error) {
 				gtr_dev->refclk_sscs[refclk] = &ssc_lookup[i];
 				break;
 			}
-- 
2.35.1.1320.gc452695387.dirty