SPI RES is the most unreliable way to identify chips because it only returns a 1-byte ID for most chips. For every given ID out there, probably a dozen incompatible flash chips match it. We already refuse to identify a chip with RES if that chip responds to RDID (3 bytes, good match), and with this patch we additionally refuse RES if the chip responds to REMS (2 bytes, still a good match). This increases matching accuracy a lot.
Besides that, the RDID/REMS response checking has been cleaned up for better readability.
Signed-off-by: Carl-Daniel Hailfinger c-d.hailfinger.devel.2006@gmx.net
Index: flashrom-spi_res_avoidance/spi.c =================================================================== --- flashrom-spi_res_avoidance/spi.c (Revision 896) +++ flashrom-spi_res_avoidance/spi.c (Arbeitskopie) @@ -385,17 +385,30 @@ { unsigned char readarr[3]; uint32_t id2; + const unsigned char allff[] = {0xff, 0xff, 0xff}; + const unsigned char all00[] = {0x00, 0x00, 0x00};
- /* Check if RDID was successful and did not return 0xff 0xff 0xff. - * In that case, RES is pointless. + /* Check if RDID is usable and does not return 0xff 0xff 0xff or + * 0x00 0x00 0x00. In that case, RES is pointless. */ - if (!spi_rdid(readarr, 3) && ((readarr[0] != 0xff) || - (readarr[1] != 0xff) || (readarr[2] != 0xff))) + if (!spi_rdid(readarr, 3) && memcmp(readarr, allff, 3) && + memcmp(readarr, all00, 3)) { + msg_cdbg("Ignoring RES in favour of RDID.\n"); return 0; + } + /* Check if REMS is usable and does not return 0xff 0xff or + * 0x00 0x00. In that case, RES is pointless. + */ + if (!spi_rems(readarr) && memcmp(readarr, allff, JEDEC_REMS_INSIZE) && + memcmp(readarr, all00, JEDEC_REMS_INSIZE)) { + msg_cdbg("Ignoring RES in favour of REMS.\n"); + return 0; + }
if (spi_res(readarr)) return 0;
+ /* FIXME: Handle the case where RES gives a 2-byte response. */ id2 = readarr[0]; printf_debug("%s: id 0x%x\n", __func__, id2); if (id2 != flash->model_id)