drm/amd/display: DSC Bit target rate debugfs write entry

[Why]
We need to be able to specify bits per pixel for DSC on any
connector.

[How]
Overwrite computed DSC target rate in dsc_cfg, with requested value.
Overwrites for both SST and MST connectors, but in different places, but the process is identical. Overwrites only if DSC is decided to be enabled on that connector.

Signed-off-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Reviewed-by: Mikita Lipski <Mikita.Lipski@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 86 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
index b4c470c75cbe..9260b27659e4 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
@@ -1423,6 +1423,18 @@ done:
 	return size;
 }
 
+/* function: read DSC target rate on the connector in bits per pixel
+ *
+ * The read function: dp_dsc_bits_per_pixel_read
+ * returns target rate of compression in bits per pixel
+ * The return is an integer: 0 or other positive integer
+ *
+ * Access it with the following command:
+ *
+ *	cat /sys/kernel/debug/dri/0/DP-X/dsc_bits_per_pixel
+ *
+ *  0 - means that DSC is disabled
+ */
 static ssize_t dp_dsc_bits_per_pixel_read(struct file *f, char __user *buf,
 				    size_t size, loff_t *pos)
 {
@@ -1480,6 +1492,79 @@ static ssize_t dp_dsc_bits_per_pixel_read(struct file *f, char __user *buf,
 	return result;
 }
 
+/* function: write DSC target rate in bits per pixel
+ *
+ * The write function: dp_dsc_bits_per_pixel_write
+ * overwrites automatically generated DSC configuration
+ * of DSC target bit rate.
+ *
+ * Also the user has to write bpp in hexidecimal
+ * rather than in decimal.
+ *
+ * Writing DSC settings is done with the following command:
+ * - To force overwrite rate (example sets to 256 bpp x 1/16):
+ *
+ *	echo 0x100 > /sys/kernel/debug/dri/0/DP-X/dsc_bits_per_pixel
+ *
+ *  - To stop overwriting and let driver find the optimal rate,
+ * set the rate to zero:
+ *
+ *	echo 0x0 > /sys/kernel/debug/dri/0/DP-X/dsc_bits_per_pixel
+ *
+ */
+static ssize_t dp_dsc_bits_per_pixel_write(struct file *f, const char __user *buf,
+				     size_t size, loff_t *pos)
+{
+	struct amdgpu_dm_connector *aconnector = file_inode(f)->i_private;
+	struct pipe_ctx *pipe_ctx;
+	int i;
+	char *wr_buf = NULL;
+	uint32_t wr_buf_size = 42;
+	int max_param_num = 1;
+	uint8_t param_nums = 0;
+	long param[1] = {0};
+
+	if (size == 0)
+		return -EINVAL;
+
+	wr_buf = kcalloc(wr_buf_size, sizeof(char), GFP_KERNEL);
+
+	if (!wr_buf) {
+		DRM_DEBUG_DRIVER("no memory to allocate write buffer\n");
+		return -ENOSPC;
+	}
+
+	if (parse_write_buffer_into_params(wr_buf, wr_buf_size,
+					    (long *)param, buf,
+					    max_param_num,
+					    &param_nums)) {
+		kfree(wr_buf);
+		return -EINVAL;
+	}
+
+	if (param_nums <= 0) {
+		DRM_DEBUG_DRIVER("user data not be read\n");
+		kfree(wr_buf);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < MAX_PIPES; i++) {
+		pipe_ctx = &aconnector->dc_link->dc->current_state->res_ctx.pipe_ctx[i];
+			if (pipe_ctx && pipe_ctx->stream &&
+			    pipe_ctx->stream->link == aconnector->dc_link)
+				break;
+	}
+
+	if (!pipe_ctx || !pipe_ctx->stream)
+		goto done;
+
+	aconnector->dsc_settings.dsc_bits_per_pixel = param[0];
+
+done:
+	kfree(wr_buf);
+	return size;
+}
+
 static ssize_t dp_dsc_pic_width_read(struct file *f, char __user *buf,
 				    size_t size, loff_t *pos)
 {
@@ -1739,6 +1824,7 @@ static const struct file_operations dp_dsc_slice_height_debugfs_fops = {
 static const struct file_operations dp_dsc_bits_per_pixel_debugfs_fops = {
 	.owner = THIS_MODULE,
 	.read = dp_dsc_bits_per_pixel_read,
+	.write = dp_dsc_bits_per_pixel_write,
 	.llseek = default_llseek
 };