Messages in this thread | | | Subject | Re: [PATCH 3/3] mailbox: sunxi-msgbox: Add a new mailbox driver | From | Samuel Holland <> | Date | Wed, 28 Feb 2018 11:19:11 -0600 |
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Hi,
On 02/28/18 02:32, Maxime Ripard wrote: > On Tue, Feb 27, 2018 at 08:27:14PM -0600, Samuel Holland wrote: >> + /* >> + * The failure path should not disable the clock or assert the reset, >> + * because the PSCI implementation in firmware relies on this device >> + * being functional. Claiming the clock in this driver is required to >> + * prevent Linux from turning it off. >> + */ >> + ret = clk_prepare_enable(clk); >> + if (ret) { >> + dev_err(dev, "Failed to enable bus clock: %d\n", ret); >> + return ret; >> + } > > You don't need it to be always on though. You only need it to be > enabled when you access the registers (on both sides I guess?). So you > could very well enable the clock in your registers accessors in Linux, > and do the same in the ARISC firmware. That should work.
It does need to always be on because the *PSCI* implementation (ATF) also uses SCPI concurrently with Linux (on a separate channel). Turning off the clock anywhere in Linux could turn it off in the middle of a PSCI SCPI call on a different CPU, causing ATF to hang in EL3 (which would be very bad).
> Maxime
Regards, Samuel
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