Hi Kishon, Vinod,

Any follow-up comments/suggestions based on my previous reply?
Or, perhaps, just keep the patch as-is to support the generic lvds phy
configuration structure?

Thanks,
Liu Ying

On Thu, 2021-04-01 at 16:36 +0800, Liu Ying wrote:

Hi Kishon,

First of all, thanks for your review.

On Wed, 2021-03-31 at 19:02 +0530, Kishon Vijay Abraham I wrote:

quoted

Hi,

On 25/03/21 2:30 pm, Liu Ying wrote:

quoted

This patch allows LVDS PHYs to be configured through
the generic functions and through a custom structure
added to the generic union.

The parameters added here are based on common LVDS PHY
implementation practices.  The set of parameters
should cover all potential users.

Cc: Kishon Vijay Abraham I <redacted>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: NXP Linux Team <redacted>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
---
v4->v5:
* Align kernel-doc style to include/linux/phy/phy.h. (Vinod)
* Trivial tweaks.
* Drop Robert's R-b tag.

v3->v4:
* Add Robert's R-b tag.

v2->v3:
* No change.

v1->v2:
* No change.

 include/linux/phy/phy-lvds.h | 32 ++++++++++++++++++++++++++++++++
 include/linux/phy/phy.h      |  4 ++++
 2 files changed, 36 insertions(+)
 create mode 100644 include/linux/phy/phy-lvds.h

diff --git a/include/linux/phy/phy-lvds.h b/include/linux/phy/phy-lvds.h
new file mode 100644
index 00000000..7a2f474
--- /dev/null
+++ b/include/linux/phy/phy-lvds.h

@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2020 NXP
+ */
+
+#ifndef __PHY_LVDS_H_
+#define __PHY_LVDS_H_
+
+/**
+ * struct phy_configure_opts_lvds - LVDS configuration set
+ * @bits_per_lane_and_dclk_cycle:	Number of bits per data lane and
+ *					differential clock cycle.

phy_set_bus_width() instead?

This member aims to configure the number of bits transmitted during a
period of time(a clock cycle). It doesn't sound like a concept of 'bus
width'?

quoted

quoted

+ * @differential_clk_rate:		Clock rate, in Hertz, of the LVDS
+ *					differential clock.

Please use clk API's to get rate.

I like your idea. But, this rate is likely runtime-configurable, e.g.,
a LVDS to HDMI chip is connected. It seems that there is no appropriate
driver to set the rate by calling clk_set_rate() then?

quoted

quoted

+ * @lanes:				Number of active, consecutive,
+ *					data lanes, starting from lane 0,
+ *					used for the transmissions.
+ * @is_slave:				Boolean, true if the phy is a slave
+ *					which works together with a master
+ *					phy to support dual link transmission,
+ *					otherwise a regular phy or a master phy.

For parameters that are known at design time, it doesn't have to be
passed from consumer driver. So all these parameters do they really have
to be passed at runtime?

Yes for all, perhaps. Details below:

1) bits_per_lane_and_dclk_cycle
i.MX8qxp LVDS phy can only do 7, while i.MX8qm LVDS phy(a different IP)
can do either 7 or 10(configurable by setting a phy register).

2) differential_clk_rate
It's likely runtime-configurable, as I mentioned above.

3) lanes
The higher color depth is, the more lanes are used:
RGB666 - 3 lanes
RGB888 - 4 lanes
RGB101010 - 5 lanes

That means a phy with 5 lanes(like i.MX8qm LVDS phy) support up to the
3 types of RGB pixels.

Though the i.MX LVDS phys don't have any register to configure the
lanes to be used, it would be good to define it for phy_validate() or
other potential phys?

4) is_slave
Any i.MX8qxp LVDS phy instance can act as a regular phy or a master phy
or a slave phy. Changing mode at runtime is probably unneeded. But,
it's difficult for the phy driver to get the mode from device tree(see
drm_of_lvds_get_port_pixels_type()), I think. Export an i.MX8qxp LVDS
phy specific function to set this instead?

Regards,
Liu Ying

quoted

Thanks
Kishon

quoted

+ *
+ * This structure is used to represent the configuration state of a LVDS phy.
+ */
+struct phy_configure_opts_lvds {
+	unsigned int	bits_per_lane_and_dclk_cycle;
+	unsigned long	differential_clk_rate;
+	unsigned int	lanes;
+	bool		is_slave;
+};
+
+#endif /* __PHY_LVDS_H_ */

diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h
index e435bdb..d450b44 100644
--- a/include/linux/phy/phy.h
+++ b/include/linux/phy/phy.h

@@ -17,6 +17,7 @@
 #include <linux/regulator/consumer.h>
 
 #include <linux/phy/phy-dp.h>
+#include <linux/phy/phy-lvds.h>
 #include <linux/phy/phy-mipi-dphy.h>
 
 struct phy;

@@ -51,10 +52,13 @@ enum phy_mode {
  *		the MIPI_DPHY phy mode.
  * @dp:		Configuration set applicable for phys supporting
  *		the DisplayPort protocol.
+ * @lvds:	Configuration set applicable for phys supporting
+ *		the LVDS phy mode.
  */
 union phy_configure_opts {
 	struct phy_configure_opts_mipi_dphy	mipi_dphy;
 	struct phy_configure_opts_dp		dp;
+	struct phy_configure_opts_lvds		lvds;
 };
 
 /**