Re: [PATCH v2 2/5] Documentation: mtd: add a DT property to set the number of dummy cycles
From: Marek Vasut <hidden>
Date: 2015-07-22 13:53:15
Also in:
linux-arm-kernel, linux-spi, lkml
On Wednesday, July 22, 2015 at 03:17:07 PM, Cyrille Pitchen wrote:
quoted hunk ↗ jump to hunk
Depending on the SPI clock frequency, the Fast Read op code and the Single/Dual Data Rate mode, the number of dummy cycles can be tuned to improve transfer speed. The actual number of dummy cycles is specific for each memory model and is provided by the manufacturer thanks to the memory datasheet. Signed-off-by: Cyrille Pitchen <redacted> --- Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt | 6 ++++++ 1 file changed, 6 insertions(+)diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txtb/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt index 2bee68103b01..4387567d8024 100644--- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt@@ -19,6 +19,11 @@ Optional properties: all chips and support for it can not be detected atruntime. Refer to your chips' datasheet to check if this is supported by your chip. +- m25p,num-dummy-cycles : Set the number of dummy cycles for Fast Read commands. + Depending on the manufacturer additional dedicated + commands are sent to the flash memory so the + controller and the memory can agree on the number of + dummy cycles to use.
Can't you just try negotiating this value at probe time, starting with some high value and see how low you can get with the negotiations ? This way, you'd be able to effectively auto-detect this value at probe-time. I might be wrong though :) Best regards, Marek Vasut -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html