[PATCH v2 1/3] scsi - a3000.c: convert m68k WD33C93 drivers to DMA API

Michael Schmitz
2022-06-30T03:33:24Z

Use dma_map_single() for a3000 driver (leave bounce buffer
logic unchanged).

Use dma_set_mask_and_coherent() to avoid explicit cache
flushes.

Compile-tested only.

CC: linux-scsi@vger.kernel.org
Link: https://lore.kernel.org/r/6d1d88ee-1cf6-c735-1e6d-bafd2096e322@gmail.com
Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

--

Changes from v1:

- restore bounce buffer allocation (dropped in v1)

Arnd Bergmann:
- reorder dma mapping and bounce buffer copy
---
drivers/scsi/a3000.c | 53 ++++++++++++++++++++++++++++++++++++--------
1 file changed, 44 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/a3000.c b/drivers/scsi/a3000.c
index dd161885eed1..2c5cb1a02e86 100644
--- a/drivers/scsi/a3000.c
+++ b/drivers/scsi/a3000.c
@@ -7,6 +7,7 @@
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
+#include <linux/dma-mapping.h>
#include <linux/module.h>

#include <asm/page.h>
@@ -25,8 +26,11 @@
struct a3000_hostdata {
struct WD33C93_hostdata wh;
struct a3000_scsiregs *regs;
+ struct device *dev;
};

+#define DMA_DIR(d) ((d == DATA_OUT_DIR) ? DMA_TO_DEVICE : DMA_FROM_DEVICE)
+
static irqreturn_t a3000_intr(int irq, void *data)
{
struct Scsi_Host *instance = data;
@@ -49,20 +53,38 @@ static irqreturn_t a3000_intr(int irq, void *data)
static int dma_setup(struct scsi_cmnd *cmd, int dir_in)
{
struct scsi_pointer *scsi_pointer = WD33C93_scsi_pointer(cmd);
+ unsigned long len = scsi_pointer->this_residual;
struct Scsi_Host *instance = cmd->device->host;
struct a3000_hostdata *hdata = shost_priv(instance);
struct WD33C93_hostdata *wh = &hdata->wh;
struct a3000_scsiregs *regs = hdata->regs;
unsigned short cntr = CNTR_PDMD | CNTR_INTEN;
- unsigned long addr = virt_to_bus(scsi_pointer->ptr);
+ dma_addr_t addr;
+
+ addr = dma_map_single(hdata->dev, scsi_pointer->ptr,
+ len, DMA_DIR(dir_in));
+ if (dma_mapping_error(hdata->dev, addr)) {
+ dev_warn(hdata->dev, "cannot map SCSI data block %p\n",
+ scsi_pointer->ptr);
+ return 1;
+ }
+ scsi_pointer->dma_handle = addr;

/*
* if the physical address has the wrong alignment, or if
* physical address is bad, or if it is a write and at the
* end of a physical memory chunk, then allocate a bounce
* buffer
+ * MSch 20220629 - only wrong alignment tested - bounce
+ * buffer returned by kmalloc is guaranteed to be aligned
*/
if (addr & A3000_XFER_MASK) {
+ WARN_ONCE(1, "Invalid alignment for DMA!");
+ /* drop useless mapping */
+ dma_unmap_single(hdata->dev, scsi_pointer->dma_handle,
+ scsi_pointer->this_residual,
+ DMA_DIR(dir_in));
+
wh->dma_bounce_len = (scsi_pointer->this_residual + 511) & ~0x1ff;
wh->dma_bounce_buffer = kmalloc(wh->dma_bounce_len,
GFP_KERNEL);
@@ -70,6 +92,7 @@ static int dma_setup(struct scsi_cmnd *cmd, int dir_in)
/* can't allocate memory; use PIO */
if (!wh->dma_bounce_buffer) {
wh->dma_bounce_len = 0;
+ scsi_pointer->dma_handle = (dma_addr_t) NULL;
return 1;
}

@@ -79,7 +102,15 @@ static int dma_setup(struct scsi_cmnd *cmd, int dir_in)
scsi_pointer->this_residual);
}

- addr = virt_to_bus(wh->dma_bounce_buffer);
+ addr = dma_map_single(hdata->dev, scsi_pointer->ptr,
+ len, DMA_DIR(dir_in));
+ if (dma_mapping_error(hdata->dev, addr)) {
+ dev_warn(hdata->dev,
+ "cannot map SCSI data block %p\n",
+ scsi_pointer->ptr);
+ return 1;
+ }
+ scsi_pointer->dma_handle = addr;
}

/* setup dma direction */
@@ -94,13 +125,7 @@ static int dma_setup(struct scsi_cmnd *cmd, int dir_in)
/* setup DMA *physical* address */
regs->ACR = addr;

- if (dir_in) {
- /* invalidate any cache */
- cache_clear(addr, scsi_pointer->this_residual);
- } else {
- /* push any dirty cache */
- cache_push(addr, scsi_pointer->this_residual);
- }
+ /* no more cache flush here - dma_map_single() takes care */

/* start DMA */
mb(); /* make sure setup is completed */
@@ -151,6 +176,10 @@ static void dma_stop(struct Scsi_Host *instance, struct scsi_cmnd *SCpnt,
regs->CNTR = CNTR_PDMD | CNTR_INTEN;
mb(); /* make sure CNTR is updated before next IO */

+ dma_unmap_single(hdata->dev, scsi_pointer->dma_handle,
+ scsi_pointer->this_residual,
+ DMA_DIR(wh->dma_dir));
+
/* copy from a bounce buffer, if necessary */
if (status && wh->dma_bounce_buffer) {
if (SCpnt) {
@@ -193,6 +222,11 @@ static int __init amiga_a3000_scsi_probe(struct platform_device *pdev)
wd33c93_regs wdregs;
struct a3000_hostdata *hdata;

+ if (dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32))) {
+ dev_warn(&pdev->dev, "cannot use 32 bit DMA\n");
+ return -ENODEV;
+ }
+
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res)
return -ENODEV;
@@ -216,6 +250,7 @@ static int __init amiga_a3000_scsi_probe(struct platform_device *pdev)
wdregs.SCMD = &regs->SCMD;

hdata = shost_priv(instance);
+ hdata->dev = &pdev->dev;
hdata->wh.no_sync = 0xff;
hdata->wh.fast = 0;
hdata->wh.dma_mode = CTRL_DMA;
--
2.17.1