>Вторник, 19 июля 2016, 20:18 +03:00 от Alexander Kurz <akurz@xxxxxxxx>: > >Hi, >I just ran into a problem resulting from patch 6e18b3a48ee4 >("mc13xxx: Define maximum SPI clock frequency global to driver"). > >On a kindle2 board the SPI communication between an iMX31 and a MC13783 >won't work at 20MHz. Unfortunately both ICs are BGA mounted blocking any >access with scope probes. Attempts to tweak the pad properties to >PAD_CTL_DRV_HIGH | PAD_CTL_SRE_FAST | PAD_CTL_100K_PU >did not solve the problem - anyway this is a battery powered device where >the original implementers took great care on long battery life, >e.g. PAD_CTL_DRV_HIGH should not be nessesary for PMIC control. > >I do not see any way to override the 20MHz bitrate from board code, and >since the PMIC access is not time critical on an ebook-reader my choice >would be rather 200kHz. > >Is there any way to override the driver supplied default max_speed_hz? >If not, my proposal is to either >* revert this patch and let the board code choose frequency >or >* reduce the speed to some common acceptable rate, e.g. 6MHz are fine > >How was this solved with other SPI devices? For me, the MC13783 with i.MX27 works fine with 20MHz. Anyway, you can change line in mc13xxx driver to: mc_dev->spi->max_speed_hz = mc_dev->spi->max_speed_hz ? : 20000000; So you can use struct spi_board_info field for specify exact frequency. --- _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox