Technical reminder about this patch: usually, for electronic stability, you'll have to raise the voltage BEFORE increasing the clock speed; on the other, you'll have to lower the voltage AFTER lowering the clock speed. You may encounter stability problem if you don't follow this order.
The patch fixes the first case, but you may end up creating the opposite problem by only moving ci_apply_disp_minimum_voltage_request(rdev) earlier in the process. But it may actually be covered by ci_send_msg_to_smc_with_parameter() or it may not be actually what ci_upload_dpm_level_enable_mask() is about.
Is this patch linked to a specific bug?
Alexandre Demers
On Wed, Nov 19, 2014 at 4:59 PM, Alexandre Demers alexandre.f.demers@gmail.com wrote:
Technical reminder about this patch: usually, for electronic stability, you'll have to raise the voltage BEFORE increasing the clock speed; on the other, you'll have to lower the voltage AFTER lowering the clock speed. You may encounter stability problem if you don't follow this order.
The patch fixes the first case, but you may end up creating the opposite problem by only moving ci_apply_disp_minimum_voltage_request(rdev) earlier in the process. But it may actually be covered by ci_send_msg_to_smc_with_parameter() or it may not be actually what ci_upload_dpm_level_enable_mask() is about.
Is this patch linked to a specific bug?
There's no specific bug and the smc actually changes the voltages and clocks internally in firmware so the driver doesn't really have to worry about that. This specific function just tells the smc to set a new voltage floor based on potentially new requirements from the display hw. I don't know of any specific problems, it's just the current recommended order from the power teams.
Alex
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