Re: [PATCH 04/10] drm/i915: Pixel Clock changes for DSI dual link

"Singh, Gaurav K" <gaurav.k.singh@xxxxxxxxx> · Fri, 05 Dec 2014 22:48:51 +0530

On 12/5/2014 10:24 PM, Siluvery, Arun wrote:
On 05/12/2014 16:33, Singh, Gaurav K wrote:

On 12/4/2014 2:57 PM, Jani Nikula wrote:
On Thu, 04 Dec 2014, Gaurav K Singh <gaurav.k.singh@xxxxxxxxx> wrote:
For dual link MIPI Panels, each port needs half of pixel clock. 
Pixel overlap
can be enabled if needed by panel, then in that case, pixel clock 
will be
increased for extra pixels.

just a question, why do we need pixel overlap?
I couldn't find more details from spec other than that when overlap is 
set some extra pixels are sent.

regards
Arun

In Front-Back video mode for MIPI Dual Link the first half of columns of 
pixel is always transmitted by MIPI Port A  and second half in MIPI Port C.
Pixel Overlap Count sets the number of Pixels to be overlapped per half 
of Scanline in Front-Back video mode. In dual link front-back mode,
pixel overlap count needs to be added to HActive to account for the 
additional pixels added due to overlap.


v2 : Address review comments by Jani
       - Removed the bit mask used for ->dual_link
       - Used DSI instead of MIPI for #define variables

Signed-off-by: Gaurav K Singh <gaurav.k.singh@xxxxxxxxx>
---
   drivers/gpu/drm/i915/i915_reg.h            |    4 ++++
   drivers/gpu/drm/i915/intel_bios.h          |    3 ++-
   drivers/gpu/drm/i915/intel_dsi.c           |    8 ++++++++
   drivers/gpu/drm/i915/intel_dsi.h           |    6 ++++++
   drivers/gpu/drm/i915/intel_dsi_panel_vbt.c |   21 
+++++++++++++++++++++
   5 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h 
b/drivers/gpu/drm/i915/i915_reg.h
index c981f5d..87149ba 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6029,6 +6029,10 @@ enum punit_power_well {
   #define GEN8_PMINTR_REDIRECT_TO_NON_DISP    (1<<31)
   #define VLV_PWRDWNUPCTL                0xA294

+#define VLV_CHICKEN_3                0x7040C
+#define  PIXEL_OVERLAP_CNT_MASK            (3 << 30)
+#define  PIXEL_OVERLAP_CNT_SHIFT        30
I didn't find this register, but does it not need + VLV_DISPLAY_BASE?

Given that I can't find the register my review is pretty shallow, but I
don't spot anything obviously wrong either. With these caveats,

Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>

This reg is available in BSpec though the bit definitions have not 
been updated in the BSpec. Also, it was communicated by the BIOS team.
+
   #define GEN6_PMISR                0x44020
   #define GEN6_PMIMR                0x44024 /* rps_lock */
   #define GEN6_PMIIR                0x44028
diff --git a/drivers/gpu/drm/i915/intel_bios.h 
b/drivers/gpu/drm/i915/intel_bios.h
index de01167..a6a8710 100644
--- a/drivers/gpu/drm/i915/intel_bios.h
+++ b/drivers/gpu/drm/i915/intel_bios.h
@@ -818,7 +818,8 @@ struct mipi_config {
   #define DUAL_LINK_PIXEL_ALT    2
       u16 dual_link:2;
       u16 lane_cnt:2;
-    u16 rsvd3:12;
+    u16 pixel_overlap:3;
+    u16 rsvd3:9;

       u16 rsvd4;

diff --git a/drivers/gpu/drm/i915/intel_dsi.c 
b/drivers/gpu/drm/i915/intel_dsi.c
index dbe52e9..4e18abd 100644
--- a/drivers/gpu/drm/i915/intel_dsi.c
+++ b/drivers/gpu/drm/i915/intel_dsi.c
@@ -111,6 +111,14 @@ static void intel_dsi_port_enable(struct 
intel_encoder *encoder)
       enum port port;
       u32 temp;

+    if (intel_dsi->dual_link == DSI_DUAL_LINK_FRONT_BACK) {
+        temp = I915_READ(VLV_CHICKEN_3);
+        temp &= ~PIXEL_OVERLAP_CNT_MASK |
+                    intel_dsi->pixel_overlap <<
+                    PIXEL_OVERLAP_CNT_SHIFT;
+        I915_WRITE(VLV_CHICKEN_3, temp);
+    }
+
       for_each_dsi_port(port, intel_dsi->ports) {
           temp = I915_READ(MIPI_PORT_CTRL(port));

diff --git a/drivers/gpu/drm/i915/intel_dsi.h 
b/drivers/gpu/drm/i915/intel_dsi.h
index f2cc2fc..8fe2064 100644
--- a/drivers/gpu/drm/i915/intel_dsi.h
+++ b/drivers/gpu/drm/i915/intel_dsi.h
@@ -28,6 +28,11 @@
   #include <drm/drm_crtc.h>
   #include "intel_drv.h"

+/* Dual Link support */
+#define DSI_DUAL_LINK_NONE        0
+#define DSI_DUAL_LINK_FRONT_BACK    1
+#define DSI_DUAL_LINK_PIXEL_ALT        2
+
   struct intel_dsi_device {
       unsigned int panel_id;
       const char *name;
@@ -105,6 +110,7 @@ struct intel_dsi {

       u8 escape_clk_div;
       u8 dual_link;
+    u8 pixel_overlap;
       u32 port_bits;
       u32 bw_timer;
       u32 dphy_reg;
diff --git a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c 
b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
index f60146f..f8c2269 100644
--- a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
+++ b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
@@ -288,6 +288,7 @@ static bool generic_init(struct 
intel_dsi_device *dsi)
       intel_dsi->lane_count = mipi_config->lane_cnt + 1;
       intel_dsi->pixel_format = 
mipi_config->videomode_color_format << 7;
       intel_dsi->dual_link = mipi_config->dual_link;
+    intel_dsi->pixel_overlap = mipi_config->pixel_overlap;

       if (intel_dsi->dual_link)
           intel_dsi->ports = ((1 << PORT_A) | (1 << PORT_C));
@@ -310,6 +311,20 @@ static bool generic_init(struct 
intel_dsi_device *dsi)

       pclk = mode->clock;

+    /* In dual link mode each port needs half of pixel clock */
+    if (intel_dsi->dual_link) {
+        pclk = pclk / 2;
+
+        /* we can enable pixel_overlap if needed by panel. In this
+         * case we need to increase the pixelclock for extra pixels
+         */
+        if (intel_dsi->dual_link == DSI_DUAL_LINK_FRONT_BACK) {
+            pclk += DIV_ROUND_UP(mode->vtotal *
+                        intel_dsi->pixel_overlap *
+                        60, 1000);
+        }
+    }
+
       /* Burst Mode Ratio
        * Target ddr frequency from VBT / non burst ddr freq
        * multiply by 100 to preserve remainder
@@ -504,6 +519,12 @@ static bool generic_init(struct 
intel_dsi_device *dsi)
       DRM_DEBUG_KMS("Clockstop %s\n", intel_dsi->clock_stop ?
                           "disabled" : "enabled");
       DRM_DEBUG_KMS("Mode %s\n", intel_dsi->operation_mode ? 
"command" : "video");
+    if (intel_dsi->dual_link == DSI_DUAL_LINK_FRONT_BACK)
+        DRM_DEBUG_KMS("Dual link: DSI_DUAL_LINK_FRONT_BACK\n");
+    else if (intel_dsi->dual_link == DSI_DUAL_LINK_PIXEL_ALT)
+        DRM_DEBUG_KMS("Dual link: DSI_DUAL_LINK_PIXEL_ALT\n");
+    else
+        DRM_DEBUG_KMS("Dual link: NONE\n");
       DRM_DEBUG_KMS("Pixel Format %d\n", intel_dsi->pixel_format);
       DRM_DEBUG_KMS("TLPX %d\n", intel_dsi->escape_clk_div);
       DRM_DEBUG_KMS("LP RX Timeout 0x%x\n", 
intel_dsi->lp_rx_timeout);
--
1.7.9.5

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