linux-kernel - [PATCH 5.1 395/405] drm/amd/display: Fix exception from AUX acquire failure

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Date:   Wed, 29 May 2019 20:06:33 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Anthony Koo <Anthony.Koo@....com>,
        Aric Cyr <Aric.Cyr@....com>, Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.1 395/405] drm/amd/display: Fix exception from AUX acquire failure

[ Upstream commit dcf1a988678e2e39ce2b4115b8ce14d208c8c481 ]

[Why]
AUX arbitration occurs between SW and FW components.
When AUX acquire fails, it causes engine->ddc to be NULL,
which leads to an exception when we try to release the AUX
engine.

[How]
When AUX engine acquire fails, it should return from the
function without trying to continue the operation.
The upper level will determine if it wants to retry.
i.e. dce_aux_transfer_with_retries will be used and retry.

Signed-off-by: Anthony Koo <Anthony.Koo@....com>
Reviewed-by: Aric Cyr <Aric.Cyr@....com>
Acked-by: Leo Li <sunpeng.li@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/dce/dce_aux.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
index 4fe3664fb4950..5ecfcb9ee8a0c 100644
--- a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
@@ -377,7 +377,6 @@ static bool acquire(
 	struct dce_aux *engine,
 	struct ddc *ddc)
 {
-
 	enum gpio_result result;
 
 	if (!is_engine_available(engine))
@@ -458,7 +457,8 @@ int dce_aux_transfer(struct ddc_service *ddc,
 	memset(&aux_rep, 0, sizeof(aux_rep));
 
 	aux_engine = ddc->ctx->dc->res_pool->engines[ddc_pin->pin_data->en];
-	acquire(aux_engine, ddc_pin);
+	if (!acquire(aux_engine, ddc_pin))
+		return -1;
 
 	if (payload->i2c_over_aux)
 		aux_req.type = AUX_TRANSACTION_TYPE_I2C;
-- 
2.20.1