linux-kernel - [PATCH v3] clk: stm32f4: fix post divisor setup for I2S/SAI PLLs

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Date:   Fri, 16 Jul 2021 18:37:05 +0200
From:   Dario Binacchi <dariobin@...ero.it>
To:     linux-clk@...r.kernel.org
Cc:     Dario Binacchi <dariobin@...ero.it>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Gabriel Fernandez <gabriel.fernandez@...com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com
Subject: [PATCH v3] clk: stm32f4: fix post divisor setup for I2S/SAI PLLs

Enabling the framebuffer leads to a system hang. Running, as a debug
hack, the store_pan() function in drivers/video/fbdev/core/fbsysfs.c
without taking the console_lock, allows to see the crash backtrace on
the serial line.

~ # echo 0 0 > /sys/class/graphics/fb0/pan

[    9.719414] Unhandled exception: IPSR = 00000005 LR = fffffff1
[    9.726937] CPU: 0 PID: 49 Comm: sh Not tainted 5.13.0-rc5 #9
[    9.733008] Hardware name: STM32 (Device Tree Support)
[    9.738296] PC is at clk_gate_is_enabled+0x0/0x28
[    9.743426] LR is at stm32f4_pll_div_set_rate+0xf/0x38
[    9.748857] pc : [<0011e4be>]    lr : [<0011f9e3>]    psr: 0100000b
[    9.755373] sp : 00bc7be0  ip : 00000000  fp : 001f3ac4
[    9.760812] r10: 002610d0  r9 : 01efe920  r8 : 00540560
[    9.766269] r7 : 02e7ddb0  r6 : 0173eed8  r5 : 00000000  r4 : 004027c0
[    9.773081] r3 : 0011e4bf  r2 : 02e7ddb0  r1 : 0173eed8  r0 : 1d3267b8
[    9.779911] xPSR: 0100000b
[    9.782719] CPU: 0 PID: 49 Comm: sh Not tainted 5.13.0-rc5 #9
[    9.788791] Hardware name: STM32 (Device Tree Support)
[    9.794120] [<0000afa1>] (unwind_backtrace) from [<0000a33f>] (show_stack+0xb/0xc)
[    9.802421] [<0000a33f>] (show_stack) from [<0000a8df>] (__invalid_entry+0x4b/0x4c)

The `pll_num' field in the post_div_data configuration contained a wrong
value which also referenced an uninitialized hardware clock when
clk_register_pll_div() was called.

Fixes: 517633ef630e ("clk: stm32f4: Add post divisor for I2S & SAI PLLs")
Signed-off-by: Dario Binacchi <dariobin@...ero.it>

---
I added Gabriel Fernandez's 'Reviewed-by' tag as requested by himself
15 days ago at https://lore.kernel.org/patchwork/patch/1450964/.

Changes in v3:
- Add Gabriel Fernandez 'Reviewed-by' tag.

Changes in v2:
- Change  'u8 pll_num' from 'stm32f4_pll_post_div_data' structure into
  'int pll_idx'.

 drivers/clk/clk-stm32f4.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/clk-stm32f4.c b/drivers/clk/clk-stm32f4.c
index 18117ce5ff85..5c75e3d906c2 100644
--- a/drivers/clk/clk-stm32f4.c
+++ b/drivers/clk/clk-stm32f4.c
@@ -526,7 +526,7 @@ struct stm32f4_pll {
 
 struct stm32f4_pll_post_div_data {
 	int idx;
-	u8 pll_num;
+	int pll_idx;
 	const char *name;
 	const char *parent;
 	u8 flag;
@@ -557,13 +557,13 @@ static const struct clk_div_table post_divr_table[] = {
 
 #define MAX_POST_DIV 3
 static const struct stm32f4_pll_post_div_data  post_div_data[MAX_POST_DIV] = {
-	{ CLK_I2SQ_PDIV, PLL_I2S, "plli2s-q-div", "plli2s-q",
+	{ CLK_I2SQ_PDIV, PLL_VCO_I2S, "plli2s-q-div", "plli2s-q",
 		CLK_SET_RATE_PARENT, STM32F4_RCC_DCKCFGR, 0, 5, 0, NULL},
 
-	{ CLK_SAIQ_PDIV, PLL_SAI, "pllsai-q-div", "pllsai-q",
+	{ CLK_SAIQ_PDIV, PLL_VCO_SAI, "pllsai-q-div", "pllsai-q",
 		CLK_SET_RATE_PARENT, STM32F4_RCC_DCKCFGR, 8, 5, 0, NULL },
 
-	{ NO_IDX, PLL_SAI, "pllsai-r-div", "pllsai-r", CLK_SET_RATE_PARENT,
+	{ NO_IDX, PLL_VCO_SAI, "pllsai-r-div", "pllsai-r", CLK_SET_RATE_PARENT,
 		STM32F4_RCC_DCKCFGR, 16, 2, 0, post_divr_table },
 };
 
@@ -1774,7 +1774,7 @@ static void __init stm32f4_rcc_init(struct device_node *np)
 				post_div->width,
 				post_div->flag_div,
 				post_div->div_table,
-				clks[post_div->pll_num],
+				clks[post_div->pll_idx],
 				&stm32f4_clk_lock);
 
 		if (post_div->idx != NO_IDX)
-- 
2.17.1