linux-kernel - [PATCH] clk: qcom: gcc-qcs404: fix initial rate of GPLL3

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Message-Id: <20241022-fix-gcc-qcs404-gpll3-v1-1-c4d30d634d19@gmail.com>
Date: Tue, 22 Oct 2024 11:45:56 +0200
From: Gabor Juhos <j4g8y7@...il.com>
To: Bjorn Andersson <andersson@...nel.org>, 
 Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>, 
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
 Taniya Das <quic_tdas@...cinc.com>
Cc: Vinod Koul <vkoul@...nel.org>, linux-arm-msm@...r.kernel.org, 
 linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org, 
 stable@...r.kernel.org, Gabor Juhos <j4g8y7@...il.com>
Subject: [PATCH] clk: qcom: gcc-qcs404: fix initial rate of GPLL3

The comment before the config of the GPLL3 PLL says that the
PLL should run at 930 MHz. In contrary to this, calculating
the frequency from the current configuration values by using
19.2 MHz as input frequency defined in 'qcs404.dtsi', it gives
921.6 MHz:

  $ xo=19200000; l=48; alpha=0x0; alpha_hi=0x0
  $ echo "$xo * ($((l)) + $(((alpha_hi << 32 | alpha) >> 8)) / 2^32)" | bc -l
  921600000.00000000000000000000

Set 'alpha_hi' in the configuration to a value used in downstream
kernels [1][2] in order to get the correct output rate:

  $ xo=19200000; l=48; alpha=0x0; alpha_hi=0x70
  $ echo "$xo * ($((l)) + $(((alpha_hi << 32 | alpha) >> 8)) / 2^32)" | bc -l
  930000000.00000000000000000000

The change is based on static code analysis, compile tested only.

[1] https://git.codelinaro.org/clo/la/kernel/msm-5.4/-/blob/kernel.lnx.5.4.r56-rel/drivers/clk/qcom/gcc-qcs404.c?ref_type=heads#L335
[2} https://git.codelinaro.org/clo/la/kernel/msm-5.15/-/blob/kernel.lnx.5.15.r49-rel/drivers/clk/qcom/gcc-qcs404.c?ref_type=heads#L127

Cc: stable@...r.kernel.org
Fixes: 652f1813c113 ("clk: qcom: gcc: Add global clock controller driver for QCS404")
Signed-off-by: Gabor Juhos <j4g8y7@...il.com>
---
Note: due to a bug in the clk_alpha_pll_configure() function, the following
patch is also needed in order for this fix to take effect:

https://lore.kernel.org/all/20241019-qcs615-mm-clockcontroller-v1-1-4cfb96d779ae@quicinc.com/
---
 drivers/clk/qcom/gcc-qcs404.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/clk/qcom/gcc-qcs404.c b/drivers/clk/qcom/gcc-qcs404.c
index c3cfd572e7c1e0a987519be2cb2050c9bc7992c7..5ca003c9bfba89bee2e626b3c35936452cc02765 100644
--- a/drivers/clk/qcom/gcc-qcs404.c
+++ b/drivers/clk/qcom/gcc-qcs404.c
@@ -131,6 +131,7 @@ static struct clk_alpha_pll gpll1_out_main = {
 /* 930MHz configuration */
 static const struct alpha_pll_config gpll3_config = {
 	.l = 48,
+	.alpha_hi = 0x70,
 	.alpha = 0x0,
 	.alpha_en_mask = BIT(24),
 	.post_div_mask = 0xf << 8,

---
base-commit: 03dc72319cee7d0dfefee9ae7041b67732f6b8cd
change-id: 20241021-fix-gcc-qcs404-gpll3-f314335c8ecf

Best regards,
-- 
Gabor Juhos <j4g8y7@...il.com>