linux-kernel - [PATCH 3/3] phy: freescale: fsl-samsung-hdmi: Improve LUT search for best clock

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Message-ID: <20250504204043.418924-3-aford173@gmail.com>
Date: Sun,  4 May 2025 15:40:42 -0500
From: Adam Ford <aford173@...il.com>
To: linux-phy@...ts.infradead.org
Cc: dominique.martinet@...ark-techno.com,
	frieder.schrempf@...tron.de,
	u.kleine-koenig@...libre.com,
	aford@...onembedded.com,
	Adam Ford <aford173@...il.com>,
	Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] phy: freescale: fsl-samsung-hdmi: Improve LUT search for best clock

Searching the look-up-table runs so long as the frequency in the
table is at or below the desired rate.  This works well in most
cases, but the next entry in the LUT might be closer to the
nominal value than the lower one.  Add some logic to check
the higer value is any closer to the nominal value and use it.

Signed-off-by: Adam Ford <aford173@...il.com>

diff --git a/drivers/phy/freescale/phy-fsl-samsung-hdmi.c b/drivers/phy/freescale/phy-fsl-samsung-hdmi.c
index a081f07681db..191c282246d9 100644
--- a/drivers/phy/freescale/phy-fsl-samsung-hdmi.c
+++ b/drivers/phy/freescale/phy-fsl-samsung-hdmi.c
@@ -510,7 +510,14 @@ static const struct phy_config *fsl_samsung_hdmi_phy_lookup_rate(unsigned long r
 		if (phy_pll_cfg[i].pixclk <= rate)
 			break;
 
-	return &phy_pll_cfg[i];
+	/* If there is an exact match, or the array has been searched, return the value*/
+	if (phy_pll_cfg[i].pixclk == rate || i + 1 > ARRAY_SIZE(phy_pll_cfg) - 1)
+		return &phy_pll_cfg[i];
+
+	/* See if the next entry is closer to nominal than this one */
+	return (abs((long) rate - (long) phy_pll_cfg[i].pixclk) <
+		abs((long) rate - (long) phy_pll_cfg[i+1].pixclk) ?
+		&phy_pll_cfg[i] : &phy_pll_cfg[i+1]);
 }
 
 static void fsl_samsung_hdmi_calculate_phy(struct phy_config *cal_phy, unsigned long rate,
-- 
2.48.1