[PATCH v6] media: mtk-vpu: Ensure alignment of 8 for DTCM buffer

[Pin-yen Lin]

From: Alexandre Courbot <acourbot at chromium.org>

When running memcpy_toio:
memcpy_toio(send_obj->share_buf, buf, len);
it was found that errors appear if len is not a multiple of 8:

[58.350841] mtk-mdp 14001000.rdma: processing failed: -22

This is because in ARM64, memcpy_toio does byte-size access
when the length is not a multiple of 8 while access to the
vpu iomem must be 4 aligned.

This patch ensures the copy of a multiple of 8 size by calling
round_up(len, 8) when copying.

Fixes: e6599adfad30 ("media: mtk-vpu: avoid unaligned access to DTCM buffer.")
Signed-off-by: Alexandre Courbot <acourbot at chromium.org>
Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld at collabora.com>
Signed-off-by: Pin-yen Lin <treapking at chromium.org>
Reviewed-by: Houlong Wei <houlong.wei at mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>

---
This is a re-send of v5 because it was marked obsolete, but this patch
is required for MT8173 platforms.

Changes in v6:
- Collect review tag

 drivers/media/platform/mediatek/vpu/mtk_vpu.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/mediatek/vpu/mtk_vpu.c b/drivers/media/platform/mediatek/vpu/mtk_vpu.c
index 5e2bc286f168..19ff4afea456 100644
--- a/drivers/media/platform/mediatek/vpu/mtk_vpu.c
+++ b/drivers/media/platform/mediatek/vpu/mtk_vpu.c
@@ -349,7 +349,22 @@ int vpu_ipi_send(struct platform_device *pdev,
 		}
 	} while (vpu_cfg_readl(vpu, HOST_TO_VPU));
 
-	memcpy_toio(send_obj->share_buf, buf, len);
+	/*
+	 * On Arm64, the memcpy_toio does byte-size access as long as address or length are
+	 * not 8 aligned. Access to the vpu iomem must be 4 aligned. Byte-size access is
+	 * not allowed and cause processing to fail. Therefore make sure the length
+	 * sent to memcpy_toio is a multiply of 8.
+	 */
+	if (len % 8 != 0) {
+		unsigned char data[sizeof(send_obj->share_buf)];
+
+		memset(data + len, 0, sizeof(data) - len);
+		memcpy(data, buf, len);
+		memcpy_toio(send_obj->share_buf, data, round_up(len, 8));
+	} else {
+		memcpy_toio(send_obj->share_buf, buf, len);
+	}
+
 	writel(len, &send_obj->len);
 	writel(id, &send_obj->id);
 
-- 
2.41.0.rc0.172.g3f132b7071-goog