linux-kernel - [PATCH] mfd: altera-sysmgr: enable raw spinlock feature for preempt-rt kernel

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Message-Id: <20211116105424.12685-1-Meng.Li@windriver.com>
Date:   Tue, 16 Nov 2021 18:54:24 +0800
From:   Meng Li <Meng.Li@...driver.com>
To:     thor.thayer@...ux.intel.com, lee.jones@...aro.org, arnd@...db.de
Cc:     linux-kernel@...r.kernel.org, meng.li@...driver.com
Subject: [PATCH] mfd: altera-sysmgr: enable raw spinlock feature for preempt-rt kernel

When booting up preempt rt kernel on stratix10 platform, there is
below calltrace:
BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:969
in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 1, name: swapper/0
Preemption disabled at:
[<ffff8000100b25b0>] __setup_irq+0xe0/0x730
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.10.78-rt54-yocto-preempt-rt #1
Hardware name: SoCFPGA Stratix 10 SoCDK (DT)
Call trace:
 ......
 ___might_sleep+0x144/0x180
 rt_spin_lock+0x34/0x9c
 regmap_lock_spinlock+0x24/0x40
 regmap_write+0x48/0x84
 a10_eccmgr_irq_unmask+0x34/0x40
 ......
 altr_edac_a10_probe+0x16c/0x2b0
 platform_drv_probe+0x60/0xb4
 ......
 ret_from_fork+0x10/0x38

Because regmap_write is invoked under preemption disabled status, and
might trigger sleep.
Recently, the commit 67021f25d952("regmap: teach regmap to use raw
spinlocks if requested in the config ") add an option for regmap to use
raw spinlock. So, enable raw spinlock in preempt-rt kernel to avoid the
might sleep issue.
Note: The commit 67021f25d952 is only in kernel v5.15, not included in
earlier versions. So, if intend to fix this issue in earlier preempt-rt
kernel, it is need to backport the 2 patches together, otherwise there
will be building issue.

Signed-off-by: Meng Li <Meng.Li@...driver.com>
---

v2:
 - improve the patch title.
 - improve the commit log. Clear which commit is depended by this patch.

---
 drivers/mfd/altera-sysmgr.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mfd/altera-sysmgr.c b/drivers/mfd/altera-sysmgr.c
index 5d3715a28b28..27271cec5d53 100644
--- a/drivers/mfd/altera-sysmgr.c
+++ b/drivers/mfd/altera-sysmgr.c
@@ -83,6 +83,9 @@ static struct regmap_config altr_sysmgr_regmap_cfg = {
 	.fast_io = true,
 	.use_single_read = true,
 	.use_single_write = true,
+#ifdef CONFIG_PREEMPT_RT
+	.use_raw_spinlock = true,
+#endif
 };

 /**
-- 
2.17.1