drm/msm: select REGULATOR

Fixes a potential error, spotted by Felipe with randconfig:

-----
drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c: In function ‘mdp4_kms_init’:
drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c:384:2: error: implicit declaration \
        of function ‘devm_regulator_get_exclusive’ [-Werror=implicit-function-declaration]
  mdp4_kms->vdd = devm_regulator_get_exclusive(&pdev->dev, "vdd");
  ^
drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c:384:16: error: assignment makes \
        pointer from integer without a cast [-Werror]
  mdp4_kms->vdd = devm_regulator_get_exclusive(&pdev->dev, "vdd");
                ^
-----

Also add a brief comment explaining the use of _get_exclusive()

Reported-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Rob Clark <robdclark@gmail.com>

2 files changed, 5 insertions, 0 deletions

diff --git a/drivers/gpu/drm/msm/Kconfig b/drivers/gpu/drm/msm/Kconfig
index 9d907c526c94..5b2a1ff95d3d 100644
--- a/drivers/gpu/drm/msm/Kconfig
+++ b/drivers/gpu/drm/msm/Kconfig
@@ -3,6 +3,7 @@ config DRM_MSM
         tristate "MSM DRM"
         depends on DRM
         depends on ARCH_QCOM || (ARM && COMPILE_TEST)
+        select REGULATOR
         select DRM_KMS_HELPER
         select DRM_PANEL
         select SHMEM
diff --git a/drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c b/drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c
index 79d804e61cc4..ac204720429e 100644
--- a/drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c
+++ b/drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c
@@ -381,6 +381,10 @@ struct msm_kms *mdp4_kms_init(struct drm_device *dev)
         if (IS_ERR(mdp4_kms->dsi_pll_vddio))
                 mdp4_kms->dsi_pll_vddio = NULL;
 
+        /* NOTE: driver for this regulator still missing upstream.. use
+         * _get_exclusive() and ignore the error if it does not exist
+         * (and hope that the bootloader left it on for us)
+         */
         mdp4_kms->vdd = devm_regulator_get_exclusive(&pdev->dev, "vdd");
         if (IS_ERR(mdp4_kms->vdd))
                 mdp4_kms->vdd = NULL;