Re: [PATCH v2 03/23] ata: sata_dwc_460ex: set dma_boundary to 0x1fff

Tejun Heo [off-list ref] writes:

On Tue, Apr 26, 2016 at 12:03:04PM +0300, Andy Shevchenko wrote:

quoted

diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c
index 7f95389..aee8873 100644
--- a/drivers/ata/sata_dwc_460ex.c
+++ b/drivers/ata/sata_dwc_460ex.c

@@ -1151,7 +1151,13 @@ static struct scsi_host_template sata_dwc_sht =3D=

 {

quoted

 	 */
 	.sg_tablesize		=3D LIBATA_MAX_PRD,
 	/* .can_queue		=3D ATA_MAX_QUEUE, */
-	.dma_boundary		=3D ATA_DMA_BOUNDARY,
+	/*
+	 * Make sure a LLI block is not created that will span 8K max FIS
+	 * boundary. If the block spans such a FIS boundary, there is a chance
+	 * that a DMA burst will cross that boundary -- this results in an
+	 * error in the host controller.
+	 */
+	.dma_boundary		=3D 0x1fff /* ATA_DMA_BOUNDARY */,

The host controller can't cross 8k boundary?  Is this for real?

From the manual:

  DMA block and burst transaction sizes are critical for DMA operation.
  (Also see the definition of "DMA transfer".)  These sizes should be
  selected properly to ensure error-free bus transfers. It is required
  that the DMA write burst transfer does not cross the 8192-byte Data
  FIS boundary, because the Transport Layer maintains the DMA state for
  the duration of the Data FIS transmission.

--=20
M=E5ns Rullg=E5rd