[PATCH v1 1/1] mmc: mmc_spi: remove custom DMA mapped buffers

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

There is no need to duplicate what SPI core or individual controller
drivers already do, i.e. mapping the buffers for DMA capable transfers.

Note, that the code, besides its redundancy, was buggy: strictly speaking
there is no guarantee, while it's true for those which can use this code
(see below), that the SPI host controller _is_ the device which does DMA.

Also see the Link tags below.

Additional notes. Currently only two SPI host controller drivers may use
premapped (by the user) DMA buffers:

  - drivers/spi/spi-au1550.c

  - drivers/spi/spi-fsl-spi.c

Both of them have DMA mapping support code. I don't expect that SPI host
controller code is worse than what has been done in mmc_spi. Hence I do
not expect any regressions here. Otherwise, I'm pretty much sure these
regressions have to be fixed in the respective drivers, and not here.

That said, remove all related pieces of DMA mapping code from mmc_spi.

Link: https://lore.kernel.org/linux-mmc/c73b9ba9-1699-2aff-e2fd-b4b4f292a3ca@raspberrypi.org/
Link: https://stackoverflow.com/questions/67620728/mmc-spi-issue-not-able-to-setup-mmc-sd-card-in-linux
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/mmc/host/mmc_spi.c | 186 +------------------------------------
 1 file changed, 5 insertions(+), 181 deletions(-)

diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c
index cc333ad67cac..2a99ffb61f8c 100644
--- a/drivers/mmc/host/mmc_spi.c
+++ b/drivers/mmc/host/mmc_spi.c
@@ -15,7 +15,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/bio.h>
-#include <linux/dma-mapping.h>
+#include <linux/dma-direction.h>
 #include <linux/crc7.h>
 #include <linux/crc-itu-t.h>
 #include <linux/scatterlist.h>
@@ -119,19 +119,14 @@ struct mmc_spi_host {
 	struct spi_transfer	status;
 	struct spi_message	readback;
 
-	/* underlying DMA-aware controller, or null */
-	struct device		*dma_dev;
-
 	/* buffer used for commands and for message "overhead" */
 	struct scratch		*data;
-	dma_addr_t		data_dma;
 
 	/* Specs say to write ones most of the time, even when the card
 	 * has no need to read its input data; and many cards won't care.
 	 * This is our source of those ones.
 	 */
 	void			*ones;
-	dma_addr_t		ones_dma;
 };
 
 
@@ -147,11 +142,8 @@ static inline int mmc_cs_off(struct mmc_spi_host *host)
 	return spi_setup(host->spi);
 }
 
-static int
-mmc_spi_readbytes(struct mmc_spi_host *host, unsigned len)
+static int mmc_spi_readbytes(struct mmc_spi_host *host, unsigned int len)
 {
-	int status;
-
 	if (len > sizeof(*host->data)) {
 		WARN_ON(1);
 		return -EIO;
@@ -159,19 +151,7 @@ mmc_spi_readbytes(struct mmc_spi_host *host, unsigned len)
 
 	host->status.len = len;
 
-	if (host->dma_dev)
-		dma_sync_single_for_device(host->dma_dev,
-				host->data_dma, sizeof(*host->data),
-				DMA_FROM_DEVICE);
-
-	status = spi_sync_locked(host->spi, &host->readback);
-
-	if (host->dma_dev)
-		dma_sync_single_for_cpu(host->dma_dev,
-				host->data_dma, sizeof(*host->data),
-				DMA_FROM_DEVICE);
-
-	return status;
+	return spi_sync_locked(host->spi, &host->readback);
 }
 
 static int mmc_spi_skip(struct mmc_spi_host *host, unsigned long timeout,
@@ -506,23 +486,11 @@ mmc_spi_command_send(struct mmc_spi_host *host,
 	t = &host->t;
 	memset(t, 0, sizeof(*t));
 	t->tx_buf = t->rx_buf = data->status;
-	t->tx_dma = t->rx_dma = host->data_dma;
 	t->len = cp - data->status;
 	t->cs_change = 1;
 	spi_message_add_tail(t, &host->m);
 
-	if (host->dma_dev) {
-		host->m.is_dma_mapped = 1;
-		dma_sync_single_for_device(host->dma_dev,
-				host->data_dma, sizeof(*host->data),
-				DMA_BIDIRECTIONAL);
-	}
 	status = spi_sync_locked(host->spi, &host->m);
-
-	if (host->dma_dev)
-		dma_sync_single_for_cpu(host->dma_dev,
-				host->data_dma, sizeof(*host->data),
-				DMA_BIDIRECTIONAL);
 	if (status < 0) {
 		dev_dbg(&host->spi->dev, "  ... write returned %d\n", status);
 		cmd->error = status;
@@ -540,9 +508,6 @@ mmc_spi_command_send(struct mmc_spi_host *host,
  * We always provide TX data for data and CRC.  The MMC/SD protocol
  * requires us to write ones; but Linux defaults to writing zeroes;
  * so we explicitly initialize it to all ones on RX paths.
- *
- * We also handle DMA mapping, so the underlying SPI controller does
- * not need to (re)do it for each message.
  */
 static void
 mmc_spi_setup_data_message(
@@ -552,11 +517,8 @@ mmc_spi_setup_data_message(
 {
 	struct spi_transfer	*t;
 	struct scratch		*scratch = host->data;
-	dma_addr_t		dma = host->data_dma;
 
 	spi_message_init(&host->m);
-	if (dma)
-		host->m.is_dma_mapped = 1;
 
 	/* for reads, readblock() skips 0xff bytes before finding
 	 * the token; for writes, this transfer issues that token.
@@ -570,8 +532,6 @@ mmc_spi_setup_data_message(
 		else
 			scratch->data_token = SPI_TOKEN_SINGLE;
 		t->tx_buf = &scratch->data_token;
-		if (dma)
-			t->tx_dma = dma + offsetof(struct scratch, data_token);
 		spi_message_add_tail(t, &host->m);
 	}
 
@@ -581,7 +541,6 @@ mmc_spi_setup_data_message(
 	t = &host->t;
 	memset(t, 0, sizeof(*t));
 	t->tx_buf = host->ones;
-	t->tx_dma = host->ones_dma;
 	/* length and actual buffer info are written later */
 	spi_message_add_tail(t, &host->m);
 
@@ -591,14 +550,9 @@ mmc_spi_setup_data_message(
 	if (direction == DMA_TO_DEVICE) {
 		/* the actual CRC may get written later */
 		t->tx_buf = &scratch->crc_val;
-		if (dma)
-			t->tx_dma = dma + offsetof(struct scratch, crc_val);
 	} else {
 		t->tx_buf = host->ones;
-		t->tx_dma = host->ones_dma;
 		t->rx_buf = &scratch->crc_val;
-		if (dma)
-			t->rx_dma = dma + offsetof(struct scratch, crc_val);
 	}
 	spi_message_add_tail(t, &host->m);
 
@@ -621,10 +575,7 @@ mmc_spi_setup_data_message(
 		memset(t, 0, sizeof(*t));
 		t->len = (direction == DMA_TO_DEVICE) ? sizeof(scratch->status) : 1;
 		t->tx_buf = host->ones;
-		t->tx_dma = host->ones_dma;
 		t->rx_buf = scratch->status;
-		if (dma)
-			t->rx_dma = dma + offsetof(struct scratch, status);
 		t->cs_change = 1;
 		spi_message_add_tail(t, &host->m);
 	}
@@ -653,23 +604,13 @@ mmc_spi_writeblock(struct mmc_spi_host *host, struct spi_transfer *t,
 
 	if (host->mmc->use_spi_crc)
 		scratch->crc_val = cpu_to_be16(crc_itu_t(0, t->tx_buf, t->len));
-	if (host->dma_dev)
-		dma_sync_single_for_device(host->dma_dev,
-				host->data_dma, sizeof(*scratch),
-				DMA_BIDIRECTIONAL);
 
 	status = spi_sync_locked(spi, &host->m);
-
 	if (status != 0) {
 		dev_dbg(&spi->dev, "write error (%d)\n", status);
 		return status;
 	}
 
-	if (host->dma_dev)
-		dma_sync_single_for_cpu(host->dma_dev,
-				host->data_dma, sizeof(*scratch),
-				DMA_BIDIRECTIONAL);
-
 	/*
 	 * Get the transmission data-response reply.  It must follow
 	 * immediately after the data block we transferred.  This reply
@@ -718,8 +659,6 @@ mmc_spi_writeblock(struct mmc_spi_host *host, struct spi_transfer *t,
 	}
 
 	t->tx_buf += t->len;
-	if (host->dma_dev)
-		t->tx_dma += t->len;
 
 	/* Return when not busy.  If we didn't collect that status yet,
 	 * we'll need some more I/O.
@@ -783,30 +722,12 @@ mmc_spi_readblock(struct mmc_spi_host *host, struct spi_transfer *t,
 	}
 	leftover = status << 1;
 
-	if (host->dma_dev) {
-		dma_sync_single_for_device(host->dma_dev,
-				host->data_dma, sizeof(*scratch),
-				DMA_BIDIRECTIONAL);
-		dma_sync_single_for_device(host->dma_dev,
-				t->rx_dma, t->len,
-				DMA_FROM_DEVICE);
-	}
-
 	status = spi_sync_locked(spi, &host->m);
 	if (status < 0) {
 		dev_dbg(&spi->dev, "read error %d\n", status);
 		return status;
 	}
 
-	if (host->dma_dev) {
-		dma_sync_single_for_cpu(host->dma_dev,
-				host->data_dma, sizeof(*scratch),
-				DMA_BIDIRECTIONAL);
-		dma_sync_single_for_cpu(host->dma_dev,
-				t->rx_dma, t->len,
-				DMA_FROM_DEVICE);
-	}
-
 	if (bitshift) {
 		/* Walk through the data and the crc and do
 		 * all the magic to get byte-aligned data.
@@ -841,8 +762,6 @@ mmc_spi_readblock(struct mmc_spi_host *host, struct spi_transfer *t,
 	}
 
 	t->rx_buf += t->len;
-	if (host->dma_dev)
-		t->rx_dma += t->len;
 
 	return 0;
 }
@@ -857,7 +776,6 @@ mmc_spi_data_do(struct mmc_spi_host *host, struct mmc_command *cmd,
 		struct mmc_data *data, u32 blk_size)
 {
 	struct spi_device	*spi = host->spi;
-	struct device		*dma_dev = host->dma_dev;
 	struct spi_transfer	*t;
 	enum dma_data_direction	direction = mmc_get_dma_dir(data);
 	struct scatterlist	*sg;
@@ -884,31 +802,8 @@ mmc_spi_data_do(struct mmc_spi_host *host, struct mmc_command *cmd,
 	 */
 	for_each_sg(data->sg, sg, data->sg_len, n_sg) {
 		int			status = 0;
-		dma_addr_t		dma_addr = 0;
 		void			*kmap_addr;
 		unsigned		length = sg->length;
-		enum dma_data_direction	dir = direction;
-
-		/* set up dma mapping for controller drivers that might
-		 * use DMA ... though they may fall back to PIO
-		 */
-		if (dma_dev) {
-			/* never invalidate whole *shared* pages ... */
-			if ((sg->offset != 0 || length != PAGE_SIZE)
-					&& dir == DMA_FROM_DEVICE)
-				dir = DMA_BIDIRECTIONAL;
-
-			dma_addr = dma_map_page(dma_dev, sg_page(sg), 0,
-						PAGE_SIZE, dir);
-			if (dma_mapping_error(dma_dev, dma_addr)) {
-				data->error = -EFAULT;
-				break;
-			}
-			if (direction == DMA_TO_DEVICE)
-				t->tx_dma = dma_addr + sg->offset;
-			else
-				t->rx_dma = dma_addr + sg->offset;
-		}
 
 		/* allow pio too; we don't allow highmem */
 		kmap_addr = kmap(sg_page(sg));
@@ -941,8 +836,6 @@ mmc_spi_data_do(struct mmc_spi_host *host, struct mmc_command *cmd,
 		if (direction == DMA_FROM_DEVICE)
 			flush_dcache_page(sg_page(sg));
 		kunmap(sg_page(sg));
-		if (dma_dev)
-			dma_unmap_page(dma_dev, dma_addr, PAGE_SIZE, dir);
 
 		if (status < 0) {
 			data->error = status;
@@ -977,21 +870,9 @@ mmc_spi_data_do(struct mmc_spi_host *host, struct mmc_command *cmd,
 		scratch->status[0] = SPI_TOKEN_STOP_TRAN;
 
 		host->early_status.tx_buf = host->early_status.rx_buf;
-		host->early_status.tx_dma = host->early_status.rx_dma;
 		host->early_status.len = statlen;
 
-		if (host->dma_dev)
-			dma_sync_single_for_device(host->dma_dev,
-					host->data_dma, sizeof(*scratch),
-					DMA_BIDIRECTIONAL);
-
 		tmp = spi_sync_locked(spi, &host->m);
-
-		if (host->dma_dev)
-			dma_sync_single_for_cpu(host->dma_dev,
-					host->data_dma, sizeof(*scratch),
-					DMA_BIDIRECTIONAL);
-
 		if (tmp < 0) {
 			if (!data->error)
 				data->error = tmp;
@@ -1265,52 +1146,6 @@ mmc_spi_detect_irq(int irq, void *mmc)
 	return IRQ_HANDLED;
 }
 
-#ifdef CONFIG_HAS_DMA
-static int mmc_spi_dma_alloc(struct mmc_spi_host *host)
-{
-	struct spi_device *spi = host->spi;
-	struct device *dev;
-
-	if (!spi->master->dev.parent->dma_mask)
-		return 0;
-
-	dev = spi->master->dev.parent;
-
-	host->ones_dma = dma_map_single(dev, host->ones, MMC_SPI_BLOCKSIZE,
-					DMA_TO_DEVICE);
-	if (dma_mapping_error(dev, host->ones_dma))
-		return -ENOMEM;
-
-	host->data_dma = dma_map_single(dev, host->data, sizeof(*host->data),
-					DMA_BIDIRECTIONAL);
-	if (dma_mapping_error(dev, host->data_dma)) {
-		dma_unmap_single(dev, host->ones_dma, MMC_SPI_BLOCKSIZE,
-				 DMA_TO_DEVICE);
-		return -ENOMEM;
-	}
-
-	dma_sync_single_for_cpu(dev, host->data_dma, sizeof(*host->data),
-				DMA_BIDIRECTIONAL);
-
-	host->dma_dev = dev;
-	return 0;
-}
-
-static void mmc_spi_dma_free(struct mmc_spi_host *host)
-{
-	if (!host->dma_dev)
-		return;
-
-	dma_unmap_single(host->dma_dev, host->ones_dma, MMC_SPI_BLOCKSIZE,
-			 DMA_TO_DEVICE);
-	dma_unmap_single(host->dma_dev, host->data_dma,	sizeof(*host->data),
-			 DMA_BIDIRECTIONAL);
-}
-#else
-static inline int mmc_spi_dma_alloc(struct mmc_spi_host *host) { return 0; }
-static inline void mmc_spi_dma_free(struct mmc_spi_host *host) {}
-#endif
-
 static int mmc_spi_probe(struct spi_device *spi)
 {
 	void			*ones;
@@ -1402,24 +1237,17 @@ static int mmc_spi_probe(struct spi_device *spi)
 			host->powerup_msecs = 250;
 	}
 
-	/* preallocate dma buffers */
+	/* Preallocate buffers */
 	host->data = kmalloc(sizeof(*host->data), GFP_KERNEL);
 	if (!host->data)
 		goto fail_nobuf1;
 
-	status = mmc_spi_dma_alloc(host);
-	if (status)
-		goto fail_dma;
-
 	/* setup message for status/busy readback */
 	spi_message_init(&host->readback);
-	host->readback.is_dma_mapped = (host->dma_dev != NULL);
 
 	spi_message_add_tail(&host->status, &host->readback);
 	host->status.tx_buf = host->ones;
-	host->status.tx_dma = host->ones_dma;
 	host->status.rx_buf = &host->data->status;
-	host->status.rx_dma = host->data_dma + offsetof(struct scratch, status);
 	host->status.cs_change = 1;
 
 	/* register card detect irq */
@@ -1464,9 +1292,8 @@ static int mmc_spi_probe(struct spi_device *spi)
 	if (!status)
 		has_ro = true;
 
-	dev_info(&spi->dev, "SD/MMC host %s%s%s%s%s\n",
+	dev_info(&spi->dev, "SD/MMC host %s%s%s%s\n",
 			dev_name(&mmc->class_dev),
-			host->dma_dev ? "" : ", no DMA",
 			has_ro ? "" : ", no WP",
 			(host->pdata && host->pdata->setpower)
 				? "" : ", no poweroff",
@@ -1477,8 +1304,6 @@ static int mmc_spi_probe(struct spi_device *spi)
 fail_gpiod_request:
 	mmc_remove_host(mmc);
 fail_glue_init:
-	mmc_spi_dma_free(host);
-fail_dma:
 	kfree(host->data);
 fail_nobuf1:
 	mmc_spi_put_pdata(spi);
@@ -1500,7 +1325,6 @@ static void mmc_spi_remove(struct spi_device *spi)
 
 	mmc_remove_host(mmc);
 
-	mmc_spi_dma_free(host);
 	kfree(host->data);
 	kfree(host->ones);
 
-- 
2.43.0.rc1.1.gbec44491f096