From b6a9e234b11d68c8d80f01ae85ffc850dfe37929 Mon Sep 17 00:00:00 2001 From: Werner Almesberger Date: Fri, 4 Jan 2013 15:41:34 -0300 Subject: [PATCH] ubb-jtag/README: ideas for increasing the speed --- ubb-jtag/README | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/ubb-jtag/README b/ubb-jtag/README index efdb38e..35acb48 100644 --- a/ubb-jtag/README +++ b/ubb-jtag/README @@ -167,6 +167,7 @@ ben# jtag jtag> cable gpio tdi=107 tdo=105 tck=109 tms=108 jtag> detect + For the next step, we need fjmem.bit, e.g., available here: http://milkymist.org/updates/fjmem.bit.bz2 @@ -188,3 +189,21 @@ jtag> detectflash 0 Since the sysfs GPIO interface is rather slow and we make things worse by swapping to compressed RAM, the loading of fjmem.bit takes about four or five minutes. + + +Going faster +------------ + +In many applications, UrJTAG will be able to run without compressed +swap and thus faster. Smaller amounts of data will also make even +slow transfers more bearable. + +To further increase the speed, a Ben-specific GPIO driver could be +written that accesses registers directly without the very long +detour through sysfs. + +Finally, even higher speeds could be reached by using the MMC +controller to send data, similar to UBB-VGA. For this purpose, CMD +and DAT0 have been left unconnected. When connecting them to each +other, they could be used to generate fake start bits, signaling +the MMC controller to begin a transfer. (See ubb-vga for details.)