linux-kernel - [PATCH 1/2] drivers: clk: zynqmp: calculate closest mux rate

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Message-ID: <20231003062153.12215-2-jay.buddhabhatti@amd.com>
Date:   Mon, 2 Oct 2023 23:21:52 -0700
From:   Jay Buddhabhatti <jay.buddhabhatti@....com>
To:     <mturquette@...libre.com>, <sboyd@...nel.org>,
        <michal.simek@....com>
CC:     <linux-clk@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Jay Buddhabhatti <jay.buddhabhatti@....com>
Subject: [PATCH 1/2] drivers: clk: zynqmp: calculate closest mux rate

Currently zynqmp clock driver is not calculating closest mux rate and
because of that Linux is not setting proper frequency for CPU and
not able to set given frequency for dynamic frequency scaling.

E.g., In current logic initial acpu clock parent and frequency as below
apll1                  0    0    0  2199999978    0     0  50000      Y
    acpu0_mux          0    0    0  2199999978    0     0  50000      Y
        acpu0_idiv1    0    0    0  2199999978    0     0  50000      Y
            acpu0      0    0    0  2199999978    0     0  50000      Y

After changing acpu frequency to 549999994 Hz using CPU freq scaling its
selecting incorrect parent which is not closest frequency.
rpll_to_xpd            0    0    0  1599999984    0     0  50000      Y
    acpu0_mux          0    0    0  1599999984    0     0  50000      Y
        acpu0_div1     0    0    0   533333328    0     0  50000      Y
            acpu0      0    0    0   533333328    0     0  50000      Y

Parent should remain same since 549999994 = 2199999978 / 4.

So use __clk_mux_determine_rate_closest() generic function to calculate
closest rate for mux clock. After this change its selecting correct
parent and correct clock rate.
apll1                  0    0    0  2199999978    0     0  50000      Y
    acpu0_mux          0    0    0  2199999978    0     0  50000      Y
        acpu0_div1     0    0    0   549999995    0     0  50000      Y
            acpu0      0    0    0   549999995    0     0  50000      Y

Signed-off-by: Jay Buddhabhatti <jay.buddhabhatti@....com>
---
 drivers/clk/zynqmp/clk-mux-zynqmp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/zynqmp/clk-mux-zynqmp.c b/drivers/clk/zynqmp/clk-mux-zynqmp.c
index 60359333f26d..9b5d3050b742 100644
--- a/drivers/clk/zynqmp/clk-mux-zynqmp.c
+++ b/drivers/clk/zynqmp/clk-mux-zynqmp.c
@@ -89,7 +89,7 @@ static int zynqmp_clk_mux_set_parent(struct clk_hw *hw, u8 index)
 static const struct clk_ops zynqmp_clk_mux_ops = {
 	.get_parent = zynqmp_clk_mux_get_parent,
 	.set_parent = zynqmp_clk_mux_set_parent,
-	.determine_rate = __clk_mux_determine_rate,
+	.determine_rate = __clk_mux_determine_rate_closest,
 };
 
 static const struct clk_ops zynqmp_clk_mux_ro_ops = {
-- 
2.17.1