On Tuesday 12 May 2009, Jeff Garzik wrote:
> > --- a/drivers/ata/Kconfig
> > +++ b/drivers/ata/Kconfig
> > @@ -4,7 +4,7 @@
> >
> > menuconfig ATA
> > tristate "Serial ATA (prod) and Parallel ATA (experimental) drivers"
> > - depends on HAS_IOMEM
> > + depends on HAS_IOMEM && HAS_DMA
> > depends on BLOCK
> > depends on !(M32R || M68K) || BROKEN
>
> What specifically is breaking?
>
> Ideally we should be able to work with PIO-only...
CONFIG_HAS_DMA is not set on architectures that are missing
asm/dma-mapping.h or fall back to asm-generic/dma-mapping-broken.h.
In the latter case, you get a link error:
drivers/built-in.o: In function `sas_issue_ata_cmd':
/home/arnd/linux/linux-2.6/drivers/scsi/libsas/sas_ata.c(.text+0x33c50): undefined reference to `dma_map_sg'
/home/arnd/linux/linux-2.6/drivers/scsi/libsas/sas_ata.c(.text+0x33ef0): undefined reference to `dma_unmap_sg'
drivers/built-in.o: In function `ata_sg_clean':
/home/arnd/linux/linux-2.6/drivers/ata/libata-core.c(.text+0x37d18): undefined reference to `dma_unmap_sg'
drivers/built-in.o: In function `ata_qc_issue':
/home/arnd/linux/linux-2.6/drivers/ata/libata-core.c(.text+0x38774): undefined reference to `dma_map_sg'
drivers/built-in.o: In function `ata_port_start':
/home/arnd/linux/linux-2.6/drivers/ata/libata-core.c(.text+0x3bf0c): undefined reference to `dmam_alloc_coherent'
A slightly less naive (but still suboptimal) fix would be the patch below.
I could not find an easy way to force all devices to use PIO, this
patch would simply fail if someone tried to set a DMA mode.
Arnd <><
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4629,6 +4629,7 @@ static unsigned int ata_dev_init_params(struct ata_device *dev,
*/
void ata_sg_clean(struct ata_queued_cmd *qc)
{
+#ifdef CONFIG_HAS_DMA
struct ata_port *ap = qc->ap;
struct scatterlist *sg = qc->sg;
int dir = qc->dma_dir;
@@ -4642,6 +4643,7 @@ void ata_sg_clean(struct ata_queued_cmd *qc)
qc->flags &= ~ATA_QCFLAG_DMAMAP;
qc->sg = NULL;
+#endif /* CONFIG_HAS_DMA */
}
/**
@@ -4743,6 +4745,7 @@ void ata_sg_init(struct ata_queued_cmd *qc, struct scatterlist *sg,
*/
static int ata_sg_setup(struct ata_queued_cmd *qc)
{
+#ifdef CONFIG_HAS_DMA
struct ata_port *ap = qc->ap;
unsigned int n_elem;
@@ -4758,6 +4761,10 @@ static int ata_sg_setup(struct ata_queued_cmd *qc)
qc->flags |= ATA_QCFLAG_DMAMAP;
return 0;
+#else
+ DPRINTK("attempted to use DMA on incompatible architecture\n");
+ return -EINVAL;
+#endif /* CONFIG_HAS_DMA */
}
/**
@@ -5450,8 +5457,12 @@ int ata_port_start(struct ata_port *ap)
{
struct device *dev = ap->dev;
+#ifdef CONFIG_HAS_DMA
ap->prd = dmam_alloc_coherent(dev, ATA_PRD_TBL_SZ, &ap->prd_dma,
GFP_KERNEL);
+#else
+ ap->prd = devres_alloc(dev, ATA_PRD_TBL_SZ, GFP_KERNEL);
+#endif /* CONFIG_HAS_DMA */
if (!ap->prd)
return -ENOMEM;
diff --git a/drivers/scsi/libsas/Kconfig b/drivers/scsi/libsas/Kconfig
index 59e00fa..e00271f 100644
--- a/drivers/scsi/libsas/Kconfig
+++ b/drivers/scsi/libsas/Kconfig
@@ -34,6 +34,7 @@ config SCSI_SAS_ATA
bool "ATA support for libsas (requires libata)"
depends on SCSI_SAS_LIBSAS
depends on ATA = y || ATA = SCSI_SAS_LIBSAS
+ depends on HAS_DMA
help
Builds in ATA support into libsas. Will necessitate
the loading of libata along with libsas.
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