Author: stefanct
Date: Sat Feb 20 21:53:46 2016
New Revision: 1933
URL: http://flashrom.org/trac/flashrom/changeset/1933
Log:
dediprog: tremendously improve performance on SF600 by ignoring the spec.
The solution was discovered in a collaborative bug hunt with testing done by
David Hendricks. The actual culprit was found by Urja Rannikko by comparing
vanilla flashrom with David's version in chromiumos.
Signed-off-by: Stefan Tauner <stefan.tau...@alumni.tuwien.ac.at>
Tested-by: David Hendricks <dhend...@chromium.org>
Acked-by: Stefan Tauner <stefan.tau...@alumni.tuwien.ac.at>
Modified:
trunk/dediprog.c
Modified: trunk/dediprog.c
==============================================================================
--- trunk/dediprog.c Sat Feb 20 21:21:58 2016 (r1932)
+++ trunk/dediprog.c Sat Feb 20 21:53:46 2016 (r1933)
@@ -694,6 +694,14 @@
if (readcnt == 0) // If we don't require a response, we are done here
return 0;
+ /* The specifications do state the possibility to set a timeout for
transceive transactions.
+ * Apparently the "timeout" is a delay, and you can use long delays to
accelerate writing - in case you
+ * can predict the time needed by the previous command or so
(untested). In any case, using this
+ * "feature" to set sane-looking timouts for the read below will
completely trash performance with
+ * SF600 and/or firmwares >= 6.0 while they seem to be benign on SF100
with firmwares <= 5.5.2. *shrug*
+ *
+ * The specification also uses only 0 in its examples, so the lesson to
learn here:
+ * "Never trust the description of an interface in the documentation
but use the example code and pray."
const uint8_t read_timeout = 10 + readcnt/512;
if (is_new_prot()) {
idx = 0;
@@ -703,6 +711,8 @@
value = min(read_timeout, 0xFF); // Possibly two bytes but we
play safe here
}
ret = dediprog_read(CMD_TRANSCEIVE, value, idx, readarr, readcnt);
+ */
+ ret = dediprog_read(CMD_TRANSCEIVE, 0, 0, readarr, readcnt);
if (ret != readcnt) {
msg_perr("Receive SPI failed, expected %i, got %i %s!\n",
readcnt, ret, libusb_error_name(ret));
return 1;
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