[PATCH 03/11] ath10k_sdio: DMA bounce buffers for read write

[silexcommon at gmail.com]

From: Alagu Sankar <alagusankar at silex-india.com>

Some SD host controllers still need bounce buffers for SDIO data
transfers. While the transfers worked fine on x86 platforms,
this is found to be required for i.MX6 based systems.

Changes are similar to and derived from the ath6kl sdio driver.

Signed-off-by: Alagu Sankar <alagusankar at silex-india.com>
---
 drivers/net/wireless/ath/ath10k/sdio.c | 59 ++++++++++++++++++++++++++++++++--
 drivers/net/wireless/ath/ath10k/sdio.h |  5 +++
 2 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/ath10k/sdio.c b/drivers/net/wireless/ath/ath10k/sdio.c
index 03a69e5..77d4fa4 100644
--- a/drivers/net/wireless/ath/ath10k/sdio.c
+++ b/drivers/net/wireless/ath/ath10k/sdio.c
@@ -34,8 +34,20 @@
 #include "trace.h"
 #include "sdio.h"
 
+#define ATH10K_SDIO_DMA_BUF_SIZE	(32 * 1024)
+
 /* inlined helper functions */
 
+/* Macro to check if DMA buffer is WORD-aligned and DMA-able.
+ * Most host controllers assume the buffer is DMA'able and will
+ * bug-check otherwise (i.e. buffers on the stack). virt_addr_valid
+ * check fails on stack memory.
+ */
+static inline bool buf_needs_bounce(const u8 *buf)
+{
+	return ((unsigned long)buf & 0x3) || !virt_addr_valid(buf);
+}
+
 static inline int ath10k_sdio_calc_txrx_padded_len(struct ath10k_sdio *ar_sdio,
 						   size_t len)
 {
@@ -303,15 +315,29 @@ static int ath10k_sdio_read(struct ath10k *ar, u32 addr, void *buf, size_t len)
 {
 	struct ath10k_sdio *ar_sdio = ath10k_sdio_priv(ar);
 	struct sdio_func *func = ar_sdio->func;
+	bool bounced = false;
+	u8 *tbuf = NULL;
 	int ret;
 
+	if (buf_needs_bounce(buf)) {
+		if (!ar_sdio->dma_buffer)
+			return -ENOMEM;
+		mutex_lock(&ar_sdio->dma_buffer_mutex);
+		tbuf = ar_sdio->dma_buffer;
+		bounced = true;
+	} else {
+		tbuf = buf;
+	}
+
 	sdio_claim_host(func);
 
-	ret = sdio_memcpy_fromio(func, buf, addr, len);
+	ret = sdio_memcpy_fromio(func, tbuf, addr, len);
 	if (ret) {
 		ath10k_warn(ar, "failed to read from address 0x%x: %d\n",
 			    addr, ret);
 		goto out;
+	} else if (bounced) {
+		memcpy(buf, tbuf, len);
 	}
 
 	ath10k_dbg(ar, ATH10K_DBG_SDIO, "sdio read addr 0x%x buf 0x%p len %zu\n",
@@ -320,6 +346,8 @@ static int ath10k_sdio_read(struct ath10k *ar, u32 addr, void *buf, size_t len)
 
 out:
 	sdio_release_host(func);
+	if (bounced)
+		mutex_unlock(&ar_sdio->dma_buffer_mutex);
 
 	return ret;
 }
@@ -328,14 +356,27 @@ static int ath10k_sdio_write(struct ath10k *ar, u32 addr, const void *buf, size_
 {
 	struct ath10k_sdio *ar_sdio = ath10k_sdio_priv(ar);
 	struct sdio_func *func = ar_sdio->func;
+	bool bounced = false;
+	u8 *tbuf = NULL;
 	int ret;
 
+	if (buf_needs_bounce(buf)) {
+		if (!ar_sdio->dma_buffer)
+			return -ENOMEM;
+		mutex_lock(&ar_sdio->dma_buffer_mutex);
+		tbuf = ar_sdio->dma_buffer;
+		memcpy(tbuf, buf, len);
+		bounced = true;
+	} else {
+		tbuf = (u8 *)buf;
+	}
+
 	sdio_claim_host(func);
 
 	/* For some reason toio() doesn't have const for the buffer, need
 	 * an ugly hack to workaround that.
 	 */
-	ret = sdio_memcpy_toio(func, addr, (void *)buf, len);
+	ret = sdio_memcpy_toio(func, addr, (void *)tbuf, len);
 	if (ret) {
 		ath10k_warn(ar, "failed to write to address 0x%x: %d\n",
 			    addr, ret);
@@ -348,6 +389,8 @@ static int ath10k_sdio_write(struct ath10k *ar, u32 addr, const void *buf, size_
 
 out:
 	sdio_release_host(func);
+	if (bounced)
+		mutex_unlock(&ar_sdio->dma_buffer_mutex);
 
 	return ret;
 }
@@ -1978,6 +2021,12 @@ static int ath10k_sdio_probe(struct sdio_func *func,
 		goto err_free_en_reg;
 	}
 
+	ar_sdio->dma_buffer = kzalloc(ATH10K_SDIO_DMA_BUF_SIZE, GFP_KERNEL);
+	if (!ar_sdio->dma_buffer) {
+		ret = -ENOMEM;
+		goto err_free_bmi_buf;
+	}
+
 	ar_sdio->func = func;
 	sdio_set_drvdata(func, ar_sdio);
 
@@ -1987,6 +2036,7 @@ static int ath10k_sdio_probe(struct sdio_func *func,
 	spin_lock_init(&ar_sdio->lock);
 	spin_lock_init(&ar_sdio->wr_async_lock);
 	mutex_init(&ar_sdio->irq_data.mtx);
+	mutex_init(&ar_sdio->dma_buffer_mutex);
 
 	INIT_LIST_HEAD(&ar_sdio->bus_req_freeq);
 	INIT_LIST_HEAD(&ar_sdio->wr_asyncq);
@@ -1995,7 +2045,7 @@ static int ath10k_sdio_probe(struct sdio_func *func,
 	ar_sdio->workqueue = create_singlethread_workqueue("ath10k_sdio_wq");
 	if (!ar_sdio->workqueue) {
 		ret = -ENOMEM;
-		goto err_free_bmi_buf;
+		goto err_dma;
 	}
 
 	for (i = 0; i < ATH10K_SDIO_BUS_REQUEST_MAX_NUM; i++)
@@ -2040,6 +2090,8 @@ static int ath10k_sdio_probe(struct sdio_func *func,
 
 err_free_wq:
 	destroy_workqueue(ar_sdio->workqueue);
+err_dma:
+	kfree(ar_sdio->dma_buffer);
 err_free_bmi_buf:
 	kfree(ar_sdio->bmi_buf);
 err_free_en_reg:
@@ -2065,6 +2117,7 @@ static void ath10k_sdio_remove(struct sdio_func *func)
 	cancel_work_sync(&ar_sdio->wr_async_work);
 	ath10k_core_unregister(ar);
 	ath10k_core_destroy(ar);
+	kfree(ar_sdio->dma_buffer);
 }
 
 static const struct sdio_device_id ath10k_sdio_devices[] = {
diff --git a/drivers/net/wireless/ath/ath10k/sdio.h b/drivers/net/wireless/ath/ath10k/sdio.h
index 4ff7b54..718b8b7 100644
--- a/drivers/net/wireless/ath/ath10k/sdio.h
+++ b/drivers/net/wireless/ath/ath10k/sdio.h
@@ -207,6 +207,11 @@ struct ath10k_sdio {
 	struct ath10k *ar;
 	struct ath10k_sdio_irq_data irq_data;
 
+	u8 *dma_buffer;
+
+	/* protects access to dma_buffer */
+	struct mutex dma_buffer_mutex;
+
 	/* temporary buffer for BMI requests */
 	u8 *bmi_buf;
 
-- 
1.9.1