From f7cba8d49a980909cea48c5b9dcfefc6e13fef0b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Dominic=20Sacr=C3=A9?= Date: Fri, 29 Apr 2016 15:48:40 +0200 Subject: [PATCH] Work around CPU stalls in the imx-sdma driver MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Replace spinlocks with raw spinlocks. This prevents preemption during the spinlock's critical section, as is the case on non PREEMPT_RT kernels. Without this patch, the following error can occur, for example when using the audio codec on an i.MX6Q SabreSD board: INFO: rcu_preempt self-detected stall on CPU { 0} (t=2100 jiffies g=106 c=105 q=93) CPU: 0 PID: 120 Comm: irq/34-sdma Not tainted 3.14.28-rt25-1.0.0_ga+g91cf351 #1 [<80014a8c>] (unwind_backtrace) from [<8001173c>] (show_stack+0x10/0x14) [<8001173c>] (show_stack) from [<806ee750>] (dump_stack+0x7c/0xc8) [<806ee750>] (dump_stack) from [<800771c8>] (rcu_check_callbacks+0x454/0x888) [<800771c8>] (rcu_check_callbacks) from [<80037f28>] (update_process_times+0x40/0x5c) [<80037f28>] (update_process_times) from [<80082230>] (tick_sched_timer+0x4c/0x78) [<80082230>] (tick_sched_timer) from [<8004bf30>] (__run_hrtimer.isra.34+0x74/0x124) [<8004bf30>] (__run_hrtimer.isra.34) from [<8004cbb0>] (hrtimer_interrupt+0x154/0x3ac) [<8004cbb0>] (hrtimer_interrupt) from [<80014464>] (twd_handler+0x30/0x38) [<80014464>] (twd_handler) from [<8006fa2c>] (handle_percpu_devid_irq+0x6c/0x84) [<8006fa2c>] (handle_percpu_devid_irq) from [<8006bc64>] (generic_handle_irq+0x2c/0x3c) [<8006bc64>] (generic_handle_irq) from [<8000ed8c>] (handle_IRQ+0x40/0x90) [<8000ed8c>] (handle_IRQ) from [<8000856c>] (gic_handle_irq+0x2c/0x5c) [<8000856c>] (gic_handle_irq) from [<80012240>] (__irq_svc+0x40/0x84) Exception stack(0xa840feb8 to 0xa840ff00) fea0: a8007a28 00000002 fec0: 00000001 0000a6a6 a80079c0 a8007a28 a83ea080 00000000 a80079c0 a83ea080 fee0: 285190f0 00000000 00000000 a840ff00 8006d04c 806f3070 20030113 ffffffff [<80012240>] (__irq_svc) from [<806f3070>] (_raw_spin_unlock_irq+0x20/0x60) [<806f3070>] (_raw_spin_unlock_irq) from [<8006d04c>] (irq_finalize_oneshot.part.37+0x70/0xcc) [<8006d04c>] (irq_finalize_oneshot.part.37) from [<8006d148>] (irq_forced_thread_fn+0x60/0x64) [<8006d148>] (irq_forced_thread_fn) from [<8006d3dc>] (irq_thread+0x138/0x1a4) [<8006d3dc>] (irq_thread) from [<8004913c>] (kthread+0xbc/0xd4) [<8004913c>] (kthread) from [<8000e538>] (ret_from_fork+0x14/0x3c) Upstream-Status: Pending Signed-off-by: Dominic Sacré --- drivers/dma/imx-sdma.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c index 31b7fed..bb7d6aa 100644 --- a/drivers/dma/imx-sdma.c +++ b/drivers/dma/imx-sdma.c @@ -408,7 +408,7 @@ struct sdma_engine { struct dma_device dma_device; struct clk *clk_ipg; struct clk *clk_ahb; - spinlock_t channel_0_lock; + raw_spinlock_t channel_0_lock; u32 script_number; struct sdma_script_start_addrs *script_addrs; const struct sdma_driver_data *drvdata; @@ -700,7 +700,7 @@ static int sdma_load_script(struct sdma_engine *sdma, void *buf, int size, return -ENOMEM; } - spin_lock_irqsave(&sdma->channel_0_lock, flags); + raw_spin_lock_irqsave(&sdma->channel_0_lock, flags); bd0->mode.command = C0_SETPM; bd0->mode.status = BD_DONE | BD_INTR | BD_WRAP | BD_EXTD; @@ -712,7 +712,7 @@ static int sdma_load_script(struct sdma_engine *sdma, void *buf, int size, ret = sdma_run_channel0(sdma); - spin_unlock_irqrestore(&sdma->channel_0_lock, flags); + raw_spin_unlock_irqrestore(&sdma->channel_0_lock, flags); if (use_iram) gen_pool_free(sdma->iram_pool, (unsigned long)buf_virt, size); @@ -979,7 +979,7 @@ static int sdma_load_context(struct sdma_channel *sdmac) dev_dbg(sdma->dev, "event_mask0 = 0x%08x\n", (u32)sdmac->event_mask[0]); dev_dbg(sdma->dev, "event_mask1 = 0x%08x\n", (u32)sdmac->event_mask[1]); - spin_lock_irqsave(&sdma->channel_0_lock, flags); + raw_spin_lock_irqsave(&sdma->channel_0_lock, flags); memset(context, 0, sizeof(*context)); context->channel_state.pc = load_address; @@ -1005,7 +1005,7 @@ static int sdma_load_context(struct sdma_channel *sdmac) bd0->ext_buffer_addr = 2048 + (sizeof(*context) / 4) * channel; ret = sdma_run_channel0(sdma); - spin_unlock_irqrestore(&sdma->channel_0_lock, flags); + raw_spin_unlock_irqrestore(&sdma->channel_0_lock, flags); sdmac->context_loaded = true; @@ -1019,7 +1019,7 @@ static int sdma_save_restore_context(struct sdma_engine *sdma, bool save) unsigned long flags; int ret; - spin_lock_irqsave(&sdma->channel_0_lock, flags); + raw_spin_lock_irqsave(&sdma->channel_0_lock, flags); if (save) bd0->mode.command = C0_GETDM; @@ -1032,7 +1032,7 @@ static int sdma_save_restore_context(struct sdma_engine *sdma, bool save) bd0->ext_buffer_addr = 2048; ret = sdma_run_channel0(sdma); - spin_unlock_irqrestore(&sdma->channel_0_lock, flags); + raw_spin_unlock_irqrestore(&sdma->channel_0_lock, flags); return ret; } @@ -2152,7 +2152,7 @@ static int sdma_probe(struct platform_device *pdev) if (!sdma) return -ENOMEM; - spin_lock_init(&sdma->channel_0_lock); + raw_spin_lock_init(&sdma->channel_0_lock); sdma->dev = &pdev->dev; sdma->drvdata = drvdata; -- 2.8.1