Re: [PATCH 1/3] RFC: AHCI: libahci is missing DMA

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On 04-12-13 13:47, Sergei Shtylyov wrote:
Hello.

On 04-12-2013 16:10, oliver@xxxxxxxxxxx wrote:

From: Oliver Schinagl <oliver@xxxxxxxxxxx>

The Allwinner sunxi platforms have patched in the following to enable
DMA. This patch enables DMA controllers for the SUNXI Architecture.

Signed-off-by: Olliver Schinagl <oliver@xxxxxxxxxxx>
---
  drivers/ata/ahci.h    | 6 ++++++
  drivers/ata/libahci.c | 8 ++++++++
  2 files changed, 14 insertions(+)

diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index 2289efdf..2bf2423 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
[...]
@@ -209,6 +210,11 @@ enum {
      PORT_DEVSLP_DSP        = (1 << 1),       /* DevSlp present */
PORT_DEVSLP_ADSE = (1 << 0), /* Aggressive DevSlp enable */

+    /* PORT_DMA bits */
+    PORT_DMA_SETUP_OFFSET    = 8, /* dma setup offset */
+ PORT_DMA_SETUP_MASK = (0xff << PORT_DMA_SETUP_OFFSET),/* dma mask */
+    PORT_DMA_SETUP_INIT    = (0x44 << 0),

Why not shift it right by PORT_DMA_SETUP_OFFSET if you do it in the next file anyway?
Verbosity and clarity I suppose, try to reduce the number of magic values. I don't know what the preferred way is as we know so little about the IP.

[...]
diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index c482f8c..d697a74 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -570,6 +570,14 @@ void ahci_start_engine(struct ata_port *ap)
      void __iomem *port_mmio = ahci_port_base(ap);
      u32 tmp;

+#ifdef CONFIG_ARCH_SUNXI
+    /* Setup DMA before DMA start */
+    tmp = readl(port_mmio + PORT_DMA);
+    tmp &= ~PORT_DMA_SETUP_MASK;
+    tmp |= PORT_DMA_SETUP_INIT << PORT_DMA_SETUP_OFFSET;
+    writel(tmp, port_mmio + PORT_DMA);
+#endif
+

   I don't think #ifdef is appropriate here.
It's not, but I was hoping Smarter devs then me would point me the right way ;)

Oliver

WBR, Sergei


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