[PATCH] sata_dwc_460ex: fix burst transaction length

[PATCH] sata_dwc_460ex: fix burst transaction length

[Christian Lamparter]

According to DesignWare DW_ahb_dmac Databook page 159,
both SRC_MSIZE and DEST_MSIZE values "are not related to
AHB bus mater HBURST bus".

The hardware uses these values as a unit of TR_WIDTHs.
As both TR_WIDTHs are hardcoded to 4 Bytes, the MSIZEs
should be 16, so the burst transaction length will be:
64 Bytes.

Cc: stable@vger.kernel.org
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
---
 drivers/ata/sata_dwc_460ex.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c
index 2fc1516..52f0614 100644
--- a/drivers/ata/sata_dwc_460ex.c
+++ b/drivers/ata/sata_dwc_460ex.c
@@ -58,7 +58,8 @@
 #define NO_IRQ		0
 #endif
 
-#define AHB_DMA_BRST_DFLT	64	/* 16 data items burst length*/
+#define AHB_DMA_BRST_DFLT	64
+#define BRST_TRANS_LEN_DFLT	16
 
 enum {
 	SATA_DWC_MAX_PORTS = 1,
@@ -381,8 +382,8 @@ static struct dma_async_tx_descriptor *dma_dwc_xfer_setup(struct ata_queued_cmd
 	}
 
 	sconf.direction = qc->dma_dir;
-	sconf.src_maxburst = AHB_DMA_BRST_DFLT;
-	sconf.dst_maxburst = AHB_DMA_BRST_DFLT;
+	sconf.src_maxburst = BRST_TRANS_LEN_DFLT;
+	sconf.dst_maxburst = BRST_TRANS_LEN_DFLT;
 	sconf.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
 	sconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
 
-- 
2.8.0.rc3

Re: [PATCH] sata_dwc_460ex: fix burst transaction length

[Andy Shevchenko]

On Thu, Apr 7, 2016 at 1:44 AM, Christian Lamparter
<chunkeey@googlemail.com> wrote:
> According to DesignWare DW_ahb_dmac Databook page 159,
> both SRC_MSIZE and DEST_MSIZE values "are not related to
> AHB bus mater HBURST bus".
>
> The hardware uses these values as a unit of TR_WIDTHs.
> As both TR_WIDTHs are hardcoded to 4 Bytes, the MSIZEs
> should be 16, so the burst transaction length will be:
> 64 Bytes.

Thanks for the patch.

Yes, Måns and I have a branch [1] to bring this driver working back.
This change is there already.
I would appreciate if you can test this on bare metal.

[1] https://bitbucket.org/andy-shev/linux/branch/topic%2Fdw%2Fsata

>
> Cc: stable@vger.kernel.org
> Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
> ---
>  drivers/ata/sata_dwc_460ex.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c
> index 2fc1516..52f0614 100644
> --- a/drivers/ata/sata_dwc_460ex.c
> +++ b/drivers/ata/sata_dwc_460ex.c
> @@ -58,7 +58,8 @@
>  #define NO_IRQ         0
>  #endif
>
> -#define AHB_DMA_BRST_DFLT      64      /* 16 data items burst length*/
> +#define AHB_DMA_BRST_DFLT      64
> +#define BRST_TRANS_LEN_DFLT    16
>
>  enum {
>         SATA_DWC_MAX_PORTS = 1,
> @@ -381,8 +382,8 @@ static struct dma_async_tx_descriptor *dma_dwc_xfer_setup(struct ata_queued_cmd
>         }
>
>         sconf.direction = qc->dma_dir;
> -       sconf.src_maxburst = AHB_DMA_BRST_DFLT;
> -       sconf.dst_maxburst = AHB_DMA_BRST_DFLT;
> +       sconf.src_maxburst = BRST_TRANS_LEN_DFLT;
> +       sconf.dst_maxburst = BRST_TRANS_LEN_DFLT;
>         sconf.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
>         sconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
>
> --
> 2.8.0.rc3
>



-- 
With Best Regards,
Andy Shevchenko