{"id":4951,"date":"2014-03-30T17:11:58","date_gmt":"2014-03-30T17:11:58","guid":{"rendered":"https:\/\/unknownerror.org\/index.php\/2014\/03\/30\/problem-about-cortex-a8-collection-of-common-programming-errors\/"},"modified":"2014-03-30T17:11:58","modified_gmt":"2014-03-30T17:11:58","slug":"problem-about-cortex-a8-collection-of-common-programming-errors","status":"publish","type":"post","link":"https:\/\/unknownerror.org\/index.php\/2014\/03\/30\/problem-about-cortex-a8-collection-of-common-programming-errors\/","title":{"rendered":"problem about cortex-a8-Collection of common programming errors"},"content":{"rendered":"<ul>\n<li><img decoding=\"async\" src=\"http:\/\/www.gravatar.com\/avatar\/368fb99f86e2264ceec0539a3746b9d3?s=32&amp;d=identicon&amp;r=PG\" \/><br \/>\nJules<br \/>\nlinux arm cross-compiling cortex-a8 directfb<br \/>\nTrying to get a working directfb for use in an embedded system based on an i.MX53 processor (which is an ARM Cortex-A8 core) running Linux 2.6.35.3 (as supplied by Freescale).I have installed a cross compiler on my i686 debian host system. The cross compiler came from the embedian.org archive, and is the gcc-4.3-arm-linux-gnueabi package (arm-linux-gnueabi-gcc (Debian 4.3.2-1.1) 4.3.2). This is supplied with glibc 2.7. This is a different version from the version on my target system, which is<\/li>\n<li><img decoding=\"async\" src=\"http:\/\/www.gravatar.com\/avatar\/09f0bc3763af4713e9b040db21618953?s=32&amp;d=identicon&amp;r=PG\" \/><br \/>\nCinar<br \/>\nlinux-kernel arm android-ndk cortex-a8 lockdown<br \/>\nI&#8217;m doing some experiments with a ARM Cortex A-8 device running Linux kernel.I can access and read the value of the L2 cache lockdown register without any problems:asm volatile (&#8220;mrc p15, 1, %0, c9, c0, 0&#8221; : &#8220;=r&#8221; (i));When I try to write the value back, the device immediately crashes:asm volatile (&#8220;mcr p15, 1, %0, c9, c0, 0&#8221; : : &#8220;r&#8221; (i));The code is running as a kernel module so there are no permission issues.I wonder if I&#8217;m missing anything special before writing that register value?<\/li>\n<li><img decoding=\"async\" src=\"http:\/\/www.gravatar.com\/avatar\/07123541fba3343f9ddb5876595b99a7?s=32&amp;d=identicon&amp;r=PG\" \/><br \/>\nAlex<br \/>\nc++ c neon cortex-a8 arm7<br \/>\nThere is a big (~100 000) array of floating point variables, and there is a threshold (also floating point).The problem is that I have to compare each one variable from the array with a threshold, but NEON flags transfer takes a really long time (~20 cycles in accordance to a profiler).Is there any efficient way to compare these values?NOTE: As rounding error doesn&#8217;t matter, I tried the following:float arr[10000]; float threshold; &#8230;.int a = arr[20]; \/\/ e.g. int t = threshold; if (t &gt; a) {.<\/li>\n<\/ul>\n<p>Web site is in building<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Jules linux arm cross-compiling cortex-a8 directfb Trying to get a working directfb for use in an embedded system based on an i.MX53 processor (which is an ARM Cortex-A8 core) running Linux 2.6.35.3 (as supplied by Freescale).I have installed a cross compiler on my i686 debian host system. The cross compiler came from the embedian.org archive, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-4951","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/posts\/4951","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/comments?post=4951"}],"version-history":[{"count":0,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/posts\/4951\/revisions"}],"wp:attachment":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/media?parent=4951"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/categories?post=4951"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/tags?post=4951"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}