[PATCH] drm/msm/dsi: avoid pinning the command buffer on every transfer

[Michael McAllister]

The command buffer is already pinned by msm_gem_kernel_new() when it is
allocated. Calling msm_gem_get_and_pin_iova() to fetch its DMA address
adds another pin for each transfer, while teardown only drops the
allocation's lifetime pin. This leaves outstanding pins on the buffer.

Use msm_gem_get_iova() to retrieve the address without taking another
pin. The allocation's existing pin keeps the mapping valid until
msm_gem_kernel_put() releases the buffer.

Fixes: 7ad0e8cf6317 ("drm/msm: Count how many times iova memory is pinned")
Signed-off-by: Michael McAllister <me@xxxxxxxxxxxxxxxxxxxxx>
---
Hi,

I ran into this while testing display teardown on the Moto G10. The DSI
command buffer is already pinned for its lifetime, so this avoids taking
another pin every time we fetch its DMA address.

I tested this as part of the G10 display fixes on 7.2.9, including display
power cycling, suspend/resume and teardown with the compositor stopped.

Thanks,
Michael

 drivers/gpu/drm/msm/dsi/dsi_host.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index d92659d80f..64fc54dff4 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -1428,7 +1428,8 @@ int dsi_dma_base_get_6g(struct msm_dsi_host *msm_host, uint64_t *dma_base)
 	if (!dma_base)
 		return -EINVAL;
 
-	return msm_gem_get_and_pin_iova(msm_host->tx_gem_obj,
+	/* The command buffer stays pinned from allocation until teardown. */
+	return msm_gem_get_iova(msm_host->tx_gem_obj,
 				priv->kms->vm, dma_base);
 }
 

base-commit: 1e59855738454b14021b64115f0090eafc7526ae
-- 
2.39.5