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Subject[PATCH] drm/bridge/synopsys: dsi: Add read feature
Date
This patch adds the DCS/GENERIC DSI read feature.

Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
---
Extra notes:
DSI read tests have been performed with DCS & GENERIC, short & long
commands, on two different panels.
The maximum fifo size (32*32-bit = 128 bytes on stm32) has been
verified too.

drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 58 +++++++++++++++++++++------
1 file changed, 45 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
index e9422d05e897..65aeb3f78b48 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
@@ -397,18 +397,46 @@ static int dw_mipi_dsi_write(struct dw_mipi_dsi *dsi,
return dw_mipi_dsi_gen_pkt_hdr_write(dsi, le32_to_cpu(word));
}

+static int dw_mipi_dsi_read(struct dw_mipi_dsi *dsi,
+ const struct mipi_dsi_msg *msg)
+{
+ int i, j, ret, len = msg->rx_len;
+ u8 *buf = msg->rx_buf;
+ u32 val;
+
+ /* Wait end of the read operation */
+ ret = readl_poll_timeout(dsi->base + DSI_CMD_PKT_STATUS,
+ val, !(val & GEN_RD_CMD_BUSY),
+ 1000, CMD_PKT_STATUS_TIMEOUT_US);
+ if (ret) {
+ dev_err(dsi->dev, "Timeout during read operation\n");
+ return ret;
+ }
+
+ for (i = 0; i < len; i += 4) {
+ /* Read fifo must not be empty before all bytes are read */
+ ret = readl_poll_timeout(dsi->base + DSI_CMD_PKT_STATUS,
+ val, !(val & GEN_PLD_R_EMPTY),
+ 1000, CMD_PKT_STATUS_TIMEOUT_US);
+ if (ret) {
+ dev_err(dsi->dev, "Read payload FIFO is empty\n");
+ return ret;
+ }
+
+ val = dsi_read(dsi, DSI_GEN_PLD_DATA);
+ for (j = 0; j < 4 && j + i < len; j++)
+ buf[i + j] = val >> (8 * j);
+ }
+
+ return ret;
+}
+
static ssize_t dw_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
const struct mipi_dsi_msg *msg)
{
struct dw_mipi_dsi *dsi = host_to_dsi(host);
struct mipi_dsi_packet packet;
- int ret;
-
- if (msg->rx_buf || msg->rx_len) {
- /* TODO dw drv improvements: implement read feature */
- dev_warn(dsi->dev, "read operations not yet implemented\n");
- return -EINVAL;
- }
+ int ret, nb_bytes;

ret = mipi_dsi_create_packet(&packet, msg);
if (ret) {
@@ -422,12 +450,16 @@ static ssize_t dw_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
if (ret)
return ret;

- /*
- * TODO Only transmitted size is returned as actual driver does
- * not support dcs/generic reads. Please update return value when
- * delivering the read feature.
- */
- return packet.size;
+ if (msg->rx_buf && msg->rx_len) {
+ ret = dw_mipi_dsi_read(dsi, msg);
+ if (ret)
+ return ret;
+ nb_bytes = msg->rx_len;
+ } else {
+ nb_bytes = packet.size;
+ }
+
+ return nb_bytes;
}

static const struct mipi_dsi_host_ops dw_mipi_dsi_host_ops = {
--
2.15.1
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