2015-02-03 17:44:42

by Sifan Naeem

Subject: [PATCH] spi: img-spfi: same edge bit set to double spfi speeds

Setting the same edge bit is required for operating at full bitrate
programmed into the SPFI control register. Without this bit set the
max operating bitrate supported would be half the maximum bitrate
supported by the img-spfi block.
It's safe to set this bit for all transactions.

Signed-off-by: Sifan Naeem <[email protected]>
---
drivers/spi/spi-img-spfi.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/spi/spi-img-spfi.c b/drivers/spi/spi-img-spfi.c
index c01567d..e6f77b8 100644
--- a/drivers/spi/spi-img-spfi.c
+++ b/drivers/spi/spi-img-spfi.c
@@ -39,6 +39,7 @@
#define SPFI_CONTROL_SOFT_RESET BIT(11)
#define SPFI_CONTROL_SEND_DMA BIT(10)
#define SPFI_CONTROL_GET_DMA BIT(9)
+#define SPFI_CONTROL_SE BIT(8)
#define SPFI_CONTROL_TMODE_SHIFT 5
#define SPFI_CONTROL_TMODE_MASK 0x7
#define SPFI_CONTROL_TMODE_SINGLE 0
@@ -435,6 +436,9 @@ static void img_spfi_config(struct spi_master *master, struct spi_device *spi,
val |= SPFI_CONTROL_CONTINUE;
spfi_writel(spfi, val, SPFI_CONTROL);

+ /* Double the transfer speed by setting Same Edge. */
+ val |= SPFI_CONTROL_SE;
+
val = spfi_readl(spfi, SPFI_PORT_STATE);
if (spi->mode & SPI_CPHA)
val |= SPFI_PORT_STATE_CK_PHASE(spi->chip_select);
--
1.7.9.5

2015-02-04 06:10:19

by Andrew Bresticker

Subject: Re: [PATCH] spi: img-spfi: same edge bit set to double spfi speeds

Hi Sifan,

On Tue, Feb 3, 2015 at 9:46 AM, Sifan Naeem <[email protected]> wrote:
> Setting the same edge bit is required for operating at full bitrate
> programmed into the SPFI control register. Without this bit set the
> max operating bitrate supported would be half the maximum bitrate
> supported by the img-spfi block.
> It's safe to set this bit for all transactions.
>
> Signed-off-by: Sifan Naeem <[email protected]>

> @@ -435,6 +436,9 @@ static void img_spfi_config(struct spi_master *master, struct spi_device *spi,
> val |= SPFI_CONTROL_CONTINUE;
> spfi_writel(spfi, val, SPFI_CONTROL);
>
> + /* Double the transfer speed by setting Same Edge. */

I'm not sure a comment here is totally necessary, but if you do want
one, I don't think "Double the transfer speed" is the best way to put
this. Something explaining what the SE bit does and that failing to
set it results in us operating at half the specified bitrate would be
more useful.