On Thu, Oct 6, 2016 at 11:55 AM, Jagan Teki <[email protected]> wrote: > On Thu, Oct 6, 2016 at 9:21 PM, George McCollister > <[email protected]> wrote: >> On Thu, Oct 6, 2016 at 10:27 AM, Jagan Teki <[email protected]> wrote: >>> On Thu, Oct 6, 2016 at 8:32 PM, George McCollister >>> <[email protected]> wrote: >>>> I'm looking into adding a sub-command to sf to protect status >>>> registers on Winbond SPI flash parts via the status register protect >>>> bits SRP0, SRP1. I propose the sub-command be named sr-protect. >>>> >>>> My use case is simple, I want to make the SPI flash read-only when the >>>> /WP pin is low. To do this I must do 'sf protect lock 0 $size' then >>>> set SRP0 to 1 and hold the /WP pin low. Although my use case doesn't >>>> require it, setting SRP1 to 1 allows either Power Supply Lock-Down or >>>> One Time Program (if supported by hardware) and I would probably add >>>> support for these as well. >>>> >>>> All of the current Winbond SPI NOR flash part datasheets that I've >>>> looked at show that the parts support the same locking implemented in >>>> stm_lock() even though SPI_FLASH_CFI_MFR_WINBOND is not in the list of >>>> vendors which use the function. I'll change this to make >>>> SPI_FLASH_CFI_MFR_WINBOND parts use stm_lock(), stm_unlock(), >>>> stm_is_locked(). >>> >>> Does stm_lock can't protect the Winbond? how different is in the >>> process of doing when compared to stm? >> >> stm_lock() does work with the Winbond parts. The issue is that you can >> simply unlock from software (stm_unlock). To make it impossible to >> write to the flash from software you must use stm_lock() then use the >> status register protect bits to prevent an unlock. > > So, you need even if stm_unlock triggered from cmd flash still lock? > then what is the point of using unlock?
stm_lock()/stm_unlock() change the block protect bits in the status register to lock/unlock flash blocks. The status register protect bits allow changes to the status register to be blocked under certain conditions (if /WP pin is low, until re-powered or permanently). > Just describe me what is the diff b/w winbond vs other stm flash in > case of lock and unlocking. I think it may be the same but if you have a part number this code is known to work with I'll get the datasheet and check. The comment above stm_lock() actually mentions a Winbond part! As far as I can tell STMicroelectronics no longer manufactures SPI Flash. > > thanks! > -- > Jagan Teki > Free Software Engineer | www.openedev.com > U-Boot, Linux | Upstream Maintainer > Hyderabad, India. _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
