From 31d329a35f519b183a7a8f5a8c4852501b800b29 Mon Sep 17 00:00:00 2001
From: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Date: Fri, 8 Apr 2022 15:51:59 +0300
Subject: drm/i915: Fix skl_pcode_try_request function
Git-commit: 9e0a1c3c3fcbf9d819d1ee584e43c87318772fdc
Patch-mainline: v5.19-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
Currently skl_pcode_try_request function doesn't
properly handle return value it gets from
snb_pcode_rw, but treats status != 0 as success,
returning true, which basically doesn't allow
to use retry/timeout mechanisms if PCode happens
to be busy and returns EGAIN or some other status
code not equal to 0.
We saw this on real hw and also tried simulating this
by always returning -EAGAIN from snb_pcode_rw for 6 times, which
currently will just result in false success, while it should
have tried until timeout is reached:
[ 22.357729] i915 0000:00:02.0: [drm:intel_cdclk_dump_config [i915]] Changing CDCLK to
307200 kHz, VCO 614400 kHz, ref 38400 kHz, bypass 19200 kHz, voltage level 0
[ 22.357831] i915 0000:00:02.0: [drm:__snb_pcode_rw [i915]] Returning EAGAIN retry 1
[ 22.357892] i915 0000:00:02.0: [drm:skl_pcode_request [i915]] Success, exiting
[ 22.357936] i915 0000:00:02.0: [drm] ERROR Failed to inform PCU about cdclk change (err -11, freq 307200)
We see en error because higher level api, still notices that status was wrong,
however we still did try only once.
We fix it by requiring _both_ the status to be 0 and
request/reply match for success(true) and function
should return failure(false) if either status turns
out to be EAGAIN, EBUSY or whatever or reply/request
masks do not match.
So now we see this in the logs:
[ 22.318667] i915 0000:00:02.0: [drm:intel_cdclk_dump_config [i915]] Changing CDCLK to
307200 kHz, VCO 614400 kHz, ref 38400 kHz, bypass 19200 kHz, voltage level 0
[ 22.318782] i915 0000:00:02.0: [drm:__snb_pcode_rw [i915]] Returning EAGAIN retry 1
[ 22.318849] i915 0000:00:02.0: [drm:__snb_pcode_rw [i915]] Returning EAGAIN retry 2
[ 22.319006] i915 0000:00:02.0: [drm:__snb_pcode_rw [i915]] Returning EAGAIN retry 3
[ 22.319091] i915 0000:00:02.0: [drm:__snb_pcode_rw [i915]] Returning EAGAIN retry 4
[ 22.319158] i915 0000:00:02.0: [drm:__snb_pcode_rw [i915]] Returning EAGAIN retry 5
[ 22.319224] i915 0000:00:02.0: [drm:__snb_pcode_rw [i915]] Returning EAGAIN retry 6
Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220408125200.9069-2-stanislav.lisovskiy@intel.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/i915/intel_pcode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/intel_pcode.c b/drivers/gpu/drm/i915/intel_pcode.c
index 391a37492ce5..fb6c43e8a02f 100644
--- a/drivers/gpu/drm/i915/intel_pcode.c
+++ b/drivers/gpu/drm/i915/intel_pcode.c
@@ -136,7 +136,7 @@ static bool skl_pcode_try_request(struct drm_i915_private *i915, u32 mbox,
{
*status = __snb_pcode_rw(i915, mbox, &request, NULL, 500, 0, true);
- return *status || ((request & reply_mask) == reply);
+ return (*status == 0) && ((request & reply_mask) == reply);
}
/**
--
2.38.1