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gma skl: Prevent race by late timeout check 

We initialize the timeout variable before the first event on the other
side (i.e. us sending a request to PCODE). With very slow debug output
sending the request itself might take longer than the timeout period.

Reorder the code to check the timeout condition only after the first
try and thereby make sure that we always try at least twice. Also issue
a debug message in case we timed out.

Change-Id: I8cdeb3e36d7eafbef8a1a8e13670f3f9838a2f38
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/20647
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
This commit is contained in:
Nico Huber 2017-07-19 14:14:34 +02:00 committed by Nico Huber
parent 234e772f42
commit 8540805c29
1 changed files with 7 additions and 4 deletions
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11
common/skylake/hw-gfx-gma-power_and_clocks_skylake.adb
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@ -283,20 +283,23 @@ package body HW.GFX.GMA.Power_And_Clocks_Skylake is
Mask => LCPLL1_CTL_PLL_LOCK);
CDClk_Change_Timeout := Time.MS_From_Now (3);
Timed_Out := False;
loop
GT_Mailbox_Write
(MBox => SKL_PCODE_CDCLK_CONTROL,
Value => SKL_CDCLK_PREPARE_FOR_CHANGE);
Timed_Out := Time.Timed_Out (CDClk_Change_Timeout);
Registers.Read (Registers.GT_MAILBOX_DATA, MBox_Data0);
if (MBox_Data0 and SKL_CDCLK_READY_FOR_CHANGE) =
SKL_CDCLK_READY_FOR_CHANGE
then
if (MBox_Data0 and SKL_CDCLK_READY_FOR_CHANGE) /= 0 then
-- Ignore timeout if we succeeded anyway.
Timed_Out := False;
exit;
end if;
exit when Timed_Out;
Timed_Out := Time.Timed_Out (CDClk_Change_Timeout);
end loop;
pragma Debug (Timed_Out, Debug.Put_Line
("ERROR: PCODE not ready for frequency change after 3ms."));
if not Timed_Out then
GT_Mailbox_Write