[PATCH v2 2/3] scsi - a2091.c: convert m68k WD33C93 drivers to DMA API

Michael Schmitz
2022-06-30T03:33:29Z

Use dma_map_single() for a2091 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:

Arnd Bergmann:
- reorder mapping and bounce buffer copy
---
drivers/scsi/a2091.c | 63 +++++++++++++++++++++++++++++++++-----------
1 file changed, 48 insertions(+), 15 deletions(-)

diff --git a/drivers/scsi/a2091.c b/drivers/scsi/a2091.c
index cf703a1ecdda..74312400468b 100644
--- a/drivers/scsi/a2091.c
+++ b/drivers/scsi/a2091.c
@@ -24,8 +24,11 @@
struct a2091_hostdata {
struct WD33C93_hostdata wh;
struct a2091_scsiregs *regs;
+ struct device *dev;
};

+#define DMA_DIR(d) ((d == DATA_OUT_DIR) ? DMA_TO_DEVICE : DMA_FROM_DEVICE)
+
static irqreturn_t a2091_intr(int irq, void *data)
{
struct Scsi_Host *instance = data;
@@ -45,15 +48,31 @@ static irqreturn_t a2091_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 a2091_hostdata *hdata = shost_priv(instance);
struct WD33C93_hostdata *wh = &hdata->wh;
struct a2091_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;

/* don't allow DMA if the physical address is bad */
if (addr & A2091_XFER_MASK) {
+ /* drop useless mapping */
+ dma_unmap_single(hdata->dev, scsi_pointer->dma_handle,
+ scsi_pointer->this_residual,
+ DMA_DIR(dir_in));
+ scsi_pointer->dma_handle = (dma_addr_t) NULL;
+
wh->dma_bounce_len = (scsi_pointer->this_residual + 511) & ~0x1ff;
wh->dma_bounce_buffer = kmalloc(wh->dma_bounce_len,
GFP_KERNEL);
@@ -64,8 +83,21 @@ static int dma_setup(struct scsi_cmnd *cmd, int dir_in)
return 1;
}

- /* get the physical address of the bounce buffer */
- addr = virt_to_bus(wh->dma_bounce_buffer);
+ if (!dir_in) {
+ /* copy to bounce buffer for a write */
+ memcpy(wh->dma_bounce_buffer, scsi_pointer->ptr,
+ scsi_pointer->this_residual);
+ }
+
+ /* will flush/invalidate cache for us */
+ addr = dma_map_single(hdata->dev, wh->dma_bounce_buffer,
+ wh->dma_bounce_len, DMA_DIR(dir_in));
+ /* can't map buffer; use PIO */
+ if (dma_mapping_error(hdata->dev, addr)) {
+ dev_warn(hdata->dev, "cannot map bounce buffer %p\n",
+ wh->dma_bounce_buffer);
+ return 1;
+ }

/* the bounce buffer may not be in the first 16M of physmem */
if (addr & A2091_XFER_MASK) {
@@ -76,11 +108,7 @@ static int dma_setup(struct scsi_cmnd *cmd, int dir_in)
return 1;
}

- if (!dir_in) {
- /* copy to bounce buffer for a write */
- memcpy(wh->dma_bounce_buffer, scsi_pointer->ptr,
- scsi_pointer->this_residual);
- }
+ scsi_pointer->dma_handle = addr;
}

/* setup dma direction */
@@ -95,13 +123,8 @@ 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 */
regs->ST_DMA = 1;

@@ -142,6 +165,10 @@ static void dma_stop(struct Scsi_Host *instance, struct scsi_cmnd *SCpnt,
/* restore the CONTROL bits (minus the direction flag) */
regs->CNTR = CNTR_PDMD | CNTR_INTEN;

+ 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 (wh->dma_dir)
@@ -178,6 +205,11 @@ static int a2091_probe(struct zorro_dev *z, const struct zorro_device_id *ent)
wd33c93_regs wdregs;
struct a2091_hostdata *hdata;

+ if (dma_set_mask_and_coherent(&z->dev, DMA_BIT_MASK(24))) {
+ dev_warn(&z->dev, "cannot use 24 bit DMA\n");
+ return -ENODEV;
+ }
+
if (!request_mem_region(z->resource.start, 256, "wd33c93"))
return -EBUSY;

@@ -198,6 +230,7 @@ static int a2091_probe(struct zorro_dev *z, const struct zorro_device_id *ent)
wdregs.SCMD = &regs->SCMD;

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