From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jerry Van Baren Date: Thu, 29 Nov 2007 16:00:20 -0500 Subject: [U-Boot-Users] BRGs on ep8248 after updating CLKIN In-Reply-To: References: Message-ID: <474F2864.4060109@ge.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Alan Bennett wrote: > When I originally supported my ep8248-style board, I had > #define CONFIG_8260_CLKIN 66000000 /* in Hz */ > > However, I noticed (after far too much time had passed) that my cpu > speed wasn't matching my expectations. (reported 230 MHz, and > expected 350 MHz). > > This was rather easily fixed by changing the CONFIG_8260_CLKIN to 100 MHz: > #define CONFIG_8260_CLKIN 100000000 /* in Hz */ > > However, my BRGs / SMC1 uart is now broke(baud-rate mismatch). Does > anyone have experience with this section of u-boot that could help me > out? > > My BRG7 is configured by u-boot(1.3+) = 0x00010078 ~ CD = 60 (0x3c). > And there is an apparent baud-rate mismatch and all the output is > garbled now. (with a scope I measured ~ 25.5 / 26 K, when I'm > expecting 38.4k) > > I think I'm missing something in the equation, but I'm not sure where > it is. If I simply update the CD to be 162 (162*38400*16 = 99,532,800 > ~ 100 MHz) the serial port is still dead. > > Any ideas? Hi Alan, I suspect that your clock is really 66MHz (read it off the crystal, that is the definitive authority). Generally BRGs don't lie - if your CONFIG_8260_CLKIN doesn't match the actual crystal, your baud rate is going to be wrong. Your baud rate is right when CONFIG_8260_CLKIN is set to 66MHz and wrong when set to 100MHz - pretty strong evidence. My theory is that your crystal is 66MHz but your CPU multiplier is misconfigured. In the 8260 the CPU multiplier is selected by the HRCW (MODCK_H) _and_ some physical pins on the CPU (MODCK[1-3]) - your 8248 may be different. HTH, gvb