linux-kernel - mmc: dw_mmc: warning with CONFIG_DMA_API

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Message-id: <001501d1cace$9b8f2b60$d2ad8220$@samsung.com>
Date:	Mon, 20 Jun 2016 17:34:48 +0900
From:	Seung-Woo Kim <sw0312.kim@...sung.com>
To:	jh80.chung@...sung.com, ulf.hansson@...aro.org,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	sw0312.kim@...sung.com
Subject: mmc: dw_mmc: warning with CONFIG_DMA_API_DEBUG

Hi folks,

During booting test on my Exynos5422 based Odroid-XU3, kernel compiled
with CONFIG_DMA_API_DEBUG reported following warning:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at lib/dma-debug.c:1096 check_unmap+0x7bc/0xb38
dwmmc_exynos 12200000.mmc: DMA-API: device driver tries to free DMA memory it has not allocated [device address=0x000000006d9d2200]
[size=128 bytes]
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.7.0-rc4 #26
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[<c0112b4c>] (unwind_backtrace) from [<c010d888>] (show_stack+0x20/0x24)
[<c010d888>] (show_stack) from [<c03fab0c>] (dump_stack+0x80/0x94)
[<c03fab0c>] (dump_stack) from [<c0123548>] (__warn+0xf8/0x110)
[<c0123548>] (__warn) from [<c01235a8>] (warn_slowpath_fmt+0x48/0x50)
[<c01235a8>] (warn_slowpath_fmt) from [<c042ac90>] (check_unmap+0x7bc/0xb38)
[<c042ac90>] (check_unmap) from [<c042b25c>] (debug_dma_unmap_sg+0x118/0x148)
[<c042b25c>] (debug_dma_unmap_sg) from [<c077512c>] (dw_mci_dma_cleanup+0x7c/0xb8)
[<c077512c>] (dw_mci_dma_cleanup) from [<c0773f24>] (dw_mci_stop_dma+0x40/0x50)
[<c0773f24>] (dw_mci_stop_dma) from [<c0777d04>] (dw_mci_tasklet_func+0x130/0x3b4)
[<c0777d04>] (dw_mci_tasklet_func) from [<c0129760>] (tasklet_action+0xb4/0x150)
[<c0129760>] (tasklet_action) from [<c0101674>] (__do_softirq+0xe4/0x3cc)
[<c0101674>] (__do_softirq) from [<c0129030>] (irq_exit+0xd0/0x10c)
[<c0129030>] (irq_exit) from [<c01778a0>] (__handle_domain_irq+0x90/0xfc)
[<c01778a0>] (__handle_domain_irq) from [<c0101548>] (gic_handle_irq+0x64/0xa8)
[<c0101548>] (gic_handle_irq) from [<c010e3d4>] (__irq_svc+0x54/0x90)
Exception stack(0xc1101ef8 to 0xc1101f40)
1ee0:                                                       00000001 00000000
1f00: 00000000 c011b600 c1100000 c110753c 00000000 c11c3984 c11074d4 c1107548
1f20: 00000000 c1101f54 c1101f58 c1101f48 c010a1fc c010a200 60000013 ffffffff
[<c010e3d4>] (__irq_svc) from [<c010a200>] (arch_cpu_idle+0x48/0x4c)
[<c010a200>] (arch_cpu_idle) from [<c01669d8>] (default_idle_call+0x30/0x3c)
[<c01669d8>] (default_idle_call) from [<c0166d3c>] (cpu_startup_entry+0x358/0x3b4)
[<c0166d3c>] (cpu_startup_entry) from [<c0aa6ab8>] (rest_init+0x94/0x98)
[<c0aa6ab8>] (rest_init) from [<c1000d58>] (start_kernel+0x3a4/0x3b0)
[<c1000d58>] (start_kernel) from [<4000807c>] (0x4000807c)
---[ end trace 256f83eed365daf0 ]---

The warning occurs because after complete callback function,
dw_mci_dmac_complete_dma() is called, then dw_mci_stop_dma() is called
again. So it causes dma_unmap_sg() is called twice for same sg. It
occurs during clock setting at booting time.

Simply, clearing host->using_dma flag on dw_mci_dmac_complete_dma() and
dw_mci_stop_dma() like following fixes the issue, but I am not sure
this approach is proper.
---
diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 2cc6123..a71c94b 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -388,6 +388,7 @@ static void dw_mci_stop_dma(struct dw_mci *host)
 	if (host->using_dma) {
 		host->dma_ops->stop(host);
 		host->dma_ops->cleanup(host);
+		host->using_dma = 0;
 	}
 
 	/* Data transfer was stopped by the interrupt handler */
@@ -455,6 +456,7 @@ static void dw_mci_dmac_complete_dma(void *arg)
 				    DMA_FROM_DEVICE);
 
 	host->dma_ops->cleanup(host);
+	host->using_dma = 0;
 
 	/*
 	 * If the card was removed, data will be NULL. No point in trying to
@@ -943,8 +945,6 @@ static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)
 	int sg_len;
 	u32 temp;
 
-	host->using_dma = 0;
-
 	/* If we don't have a channel, we can't do DMA */
 	if (!host->use_dma)
 		return -ENODEV;
---

Best Regards,
- Seung-Woo Kim