On Mon 04 Nov 2024 at 06:18, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > On 11/4/24 00:43, Jerome Brunet wrote: > >>>> +/* >>>> + * PMBus write protect forced mode: >>>> + * PMBus may come up with a variety of write protection configuration. >>>> + * 'pmbus_wp' may be used if a particular write protection is necessary. >>>> + * The ability to actually alter the protection may also depend on the chip >>>> + * so the actual runtime write protection configuration may differ from >>>> + * the requested one. pmbus_core currently support the following value: >>>> + * - 0: write protection removed >>>> + * - 1: write protection fully enabled, including OPERATION and VOUT_COMMAND >>>> + * registers. Chips essentially become read-only with this. >>> >>> Would it be desirable to also suppport the ability to set the output voltage >>> but not limits (PB_WP_VOUT) ? >> I was starting simple, it is doable sure. >> It is not something I will be able to test on actual since does not >> support that. >> Do you want me to add "2: write protection enable execpt for >> VOUT_COMMAND." ? >> > > Please add it. I have a number of PMBus test boards and will be able to test it. > > Thee are three options, though. Per specification: Any preference for the value mapped to each mode ? Using the one from the spec does not seem practical (32768, 16384, 8192). The bit number, maybe (7, 6, 5) ? or just by order strongest locking ? > > 1000 0000 Disable all writes except to the WRITE_PROTECT command 3 > 0100 0000 Disable all writes except to the WRITE_PROTECT, OPERATION and > PAGE commands 2 > 0010 0000 Disable all writes except to the WRITE_PROTECT, OPERATION, > PAGE, ON_OFF_CONFIG and VOUT_COMMAND commands 1 ? > > The driver uses OPERATION and VOUT_COMMAND, so we should have options > to disable them separately. It may be desirable, for example, to be able > to turn on a regulator but not to change the voltages. Also, since > full write protection also disables writes to the page register, > the impact of full write protection on multi-page chips needs to be > documented. Noted. I'll update the documentation. > > Thanks, > Guenter -- Jerome
