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Re: [PATCH] ide: New libata driver for OCTEON SOC Compact Flash interfac

To: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Subject: Re: [PATCH] ide: New libata driver for OCTEON SOC Compact Flash interface.
From: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Date: Sat, 22 Nov 2008 18:13:11 +0300
Cc: David Daney <ddaney@caviumnetworks.com>, linux-ide@vger.kernel.org, linux-mips <linux-mips@linux-mips.org>
In-reply-to: <49280FC5.3040608@ru.mvista.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <49261BE5.2010406@caviumnetworks.com> <49280FC5.3040608@ru.mvista.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Thunderbird 2.0.0.18 (Windows/20081105)
Hello, I wrote:

As part of our efforts to get the Cavium OCTEON processor support
merged (see: http://marc.info/?l=linux-mips&m=122704699515601), we
have this CF driver for your consideration.

Most OCTEON variants have *no* DMA or interrupt support on the CF
interface so for these, only PIO is supported.  Although if DMA is
available, we do take advantage of it.

The register definitions are part of the chip support patch set
mentioned above, and are not included here.

At this point I would like to get feedback on the patch and would
expect that it would merge via the linux-mips tree along with the rest
of the chip support.

Thanks,

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
[...]
diff --git a/drivers/ata/pata_octeon_cf.c b/drivers/ata/pata_octeon_cf.c
new file mode 100644
index 0000000..e8712c0
--- /dev/null
+++ b/drivers/ata/pata_octeon_cf.c
@@ -0,0 +1,942 @@
[...]
+/**
+ * Get the status of the DMA engine. The results of this function
+ * must emulate the BMDMA engine expected by libata.
+ *
+ * @ap:     ATA port to check status on
+ *
+ * Returns BMDMA status bits
+ */
+static uint8_t octeon_cf_bmdma_status(struct ata_port *ap)
+{
+    struct octeon_cf_data *ocd = ap->dev->platform_data;
+    cvmx_mio_boot_dma_intx_t mio_boot_dma_int;
+    cvmx_mio_boot_dma_cfgx_t mio_boot_dma_cfg;
+    uint8_t result = 0;
+
+    mio_boot_dma_int.u64 =
+        cvmx_read_csr(CVMX_MIO_BOOT_DMA_INTX(ocd->dma_engine));
+    if (mio_boot_dma_int.s.done)
+        result |= ATA_DMA_INTR;

But if you're saying that there is only DMA completion inetrrupt, you *cannot* completely emulate SFF-8038i BMDMA since its interrupt status is the (delayed) IDE INTRQ status. I suggest that you move away from the emulation -- Alan has said it's possible.

My suggestion then is not to emulate the ATA_DMA_INTR bit (always returning it as 0) and use:

mio_boot_dma_int.u64 = cvmx_read_csr(CVMX_MIO_BOOT_DMA_INTX(ocd->dma_engine));
   if (mio_boot_dma_int.s.done)

directly in octeon_cf_interrupt().

  Also, this fragment of octeon_cf_bmdma_status() looks doubtful to me:

+    else if (mio_boot_dma_cfg.s.size != 0xfffff)
+ result |= ATA_DMA_ERR;

I suppose this only makes sense when DMA interrupt is active. What does this bitfield mean?

MBR, Sergei



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