Re: [PATCH 3/5] sata_dwc: Add support ATAPI transfer

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Hello.

On 10-05-2012 8:17, Thang Q. Nguyen wrote:

Signed-off-by: Thang Q. Nguyen<tqnguyen@xxxxxxx>
---
  drivers/ata/sata_dwc_460ex.c |   64 ++++++++++++++++++++++++++++++++++++++++--
  1 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c
index 937aeb3..6175e01 100755
--- a/drivers/ata/sata_dwc_460ex.c
+++ b/drivers/ata/sata_dwc_460ex.c
[...]
@@ -1385,6 +1389,58 @@ static void sata_dwc_port_stop(struct ata_port *ap)
  	ap->private_data = NULL;
  }

+/**
+ * sata_dwc_check_atapi_dma - Filter ATAPI cmds which are unsuitable for DMA.
+ * @qc: queued command to check for chipset/DMA compatibility.
+ *
+ * The bmdma engines cannot handle speculative data sizes (bytecount
+ * under/over flow). So only allow DMA for data transfer commands with
+ * known data sizes.
+ */
+static int sata_dwc_check_atapi_dma(struct ata_queued_cmd *qc)
+{
[...]
+
+		/* -45150 (FFFF4FA2) to -1 (FFFFFFFF) shall use PIO mode */

   Sector numbers are unsigned entities.

+		if (scmd->cmnd[0] == WRITE_10) {
+			lba = (scmd->cmnd[2] << 24) |
+				  (scmd->cmnd[3] << 16) |
+				  (scmd->cmnd[4] << 8) |
+				   scmd->cmnd[5];
+			if (lba>= 0xFFFF4FA2)
+				pio = 1;
+		}
+		/*
+		* WORK AROUND: Fix DMA issue when blank CD/DVD disc in the drive
+		* and user use the 'fdisk -l' command. No DMA data returned so
+		* we can not complete the QC.

The user shouldn't use 'fdisk' command on CD/DVD disks. On the other hand, he could use something like 'hdparm -t' od 'dd' with offset in which case I'm not sure this heuristics will work.

+		*/
+		else if (scmd->cmnd[0] == READ_10) {
+			lba = (scmd->cmnd[2] << 24) |
+				  (scmd->cmnd[3] << 16) |
+				  (scmd->cmnd[4] << 8) |
+				   scmd->cmnd[5];
+			if (lba < 0x20)
+				pio = 1;
+		}
+	}
+	return pio;
+}
+
  /*
   * Function : sata_dwc_exec_command_by_tag
   * arguments : ata_port *ap, ata_taskfile *tf, u8 tag, u32 cmd_issued

WBR, Sergei
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