Jason McMullan <[EMAIL PROTECTED]> wrote: > This commit adds MTD support for the M25P80 (1Mx8) and the M25P40 (512kx8) > SPI Flash components from ST Microelectronics. > > Tested with the M25P40, but should work for the M25P80 according > to the spec sheet. > ---
Nice. I have a few minor comments below. Could you add some information on how to obtain data sheets for these things? I had some difficulty finding it. FWIW, I think it's here: http://www.numonyx.com/en-US/MemoryProducts/NOR/Pages/M25PTechnicalDocuments.aspx > +struct stmicro_spi_flash_params { > + uint8_t esig; > + /* Log2 of page size in power-of-two mode */ Do these chips support anything but power-of-two page sizes? I always thought that was an AT45 DataFlash peculiarity... I can't find anything in the M25P80 indicating that the page size can be different from 256... > + uint8_t l2_page_size; > +/* > + * Assemble the address part of a command for STMicro devices in > + * non-power-of-two page size mode. > + */ This comment is misleading. The below code only works for power-of-two page sizes. > +static void stmicro_build_address(struct stmicro_spi_flash *stm, u8 *cmd, > u32 offset) > +{ > + unsigned long page_addr; > + unsigned long byte_addr; > + unsigned long page_size; > + unsigned int page_shift; > + > + /* > + * The "extra" space per page is the power-of-two page size > + * divided by 32. > + */ This comment is misleading too. There's no "extra" space in the calculations below... > + page_shift = stm->params->l2_page_size; > + page_size = (1 << page_shift); > + page_addr = offset / page_size; > + byte_addr = offset % page_size; ...which means that you can make these operations cheaper by using shift and mask instead of divide and modulo. Though I suppose a clever compiler might figure that out on its own... > +static int stmicro_write(struct spi_flash *flash, > + u32 offset, size_t len, const void *buf) > +{ > + struct stmicro_spi_flash *stm = to_stmicro_spi_flash(flash); > + unsigned long page_addr; > + unsigned long byte_addr; > + unsigned long page_size; > + unsigned int page_shift; > + size_t chunk_len; > + size_t actual; > + int ret; > + u8 cmd[4]; > + > + page_shift = stm->params->l2_page_size; > + page_size = (1 << page_shift); > + page_addr = offset / page_size; > + byte_addr = offset % page_size; Same thing here. Could you have a look at the disassembly to see if the compiler _is_ clever enough to optimize away the divide/modulo? Haavard ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ U-Boot-Users mailing list U-Boot-Users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/u-boot-users
