Skip to content

Commit

Permalink
drm/vc4: Adjust modes in DSI to work around the integer PLL divider.
Browse files Browse the repository at this point in the history 
BCM2835's PLLD_DSI1 divider doesn't give us many choices for our pixel
clocks, so to support panels on the Raspberry Pi we need to set a
higher pixel clock rate than requested and adjust the mode we program
to extend out the HFP so that the refresh rate matches.

v2: Drop an unfinished comment (caught by Noralf)

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: http://patchwork.freedesktop.org/patch/msgid/20170511235625.22427-2-eric@anholt.net
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
  • Loading branch information
@anholt
anholt committed May 16, 2017
1 parent fdb888d commit 86c1b9e
Showing 1 changed file with 86 additions and 26 deletions.
112 changes: 86 additions & 26 deletions drivers/gpu/drm/vc4/vc4_dsi.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -519,7 +519,8 @@ struct vc4_dsi {
/* DSI channel for the panel we're connected to. */
u32 channel;
u32 lanes;
enum mipi_dsi_pixel_format format;
u32 format;
u32 divider;
u32 mode_flags;

/* Input clock from CPRMAN to the digital PHY, for the DSI
Expand Down Expand Up @@ -906,13 +907,67 @@ static void vc4_dsi_encoder_disable(struct drm_encoder *encoder)
pm_runtime_put(dev);
}

/* Extends the mode's blank intervals to handle BCM2835's integer-only
* DSI PLL divider.
*
* On 2835, PLLD is set to 2Ghz, and may not be changed by the display
* driver since most peripherals are hanging off of the PLLD_PER
* divider. PLLD_DSI1, which drives our DSI bit clock (and therefore
* the pixel clock), only has an integer divider off of DSI.
*
* To get our panel mode to refresh at the expected 60Hz, we need to
* extend the horizontal blank time. This means we drive a
* higher-than-expected clock rate to the panel, but that's what the
* firmware does too.
*/
static bool vc4_dsi_encoder_mode_fixup(struct drm_encoder *encoder,
const struct drm_display_mode *mode,
struct drm_display_mode *adjusted_mode)
{
struct vc4_dsi_encoder *vc4_encoder = to_vc4_dsi_encoder(encoder);
struct vc4_dsi *dsi = vc4_encoder->dsi;
struct clk *phy_parent = clk_get_parent(dsi->pll_phy_clock);
unsigned long parent_rate = clk_get_rate(phy_parent);
unsigned long pixel_clock_hz = mode->clock * 1000;
unsigned long pll_clock = pixel_clock_hz * dsi->divider;
int divider;

/* Find what divider gets us a faster clock than the requested
* pixel clock.
*/
for (divider = 1; divider < 8; divider++) {
if (parent_rate / divider < pll_clock) {
divider--;
break;
}
}

/* Now that we've picked a PLL divider, calculate back to its
* pixel clock.
*/
pll_clock = parent_rate / divider;
pixel_clock_hz = pll_clock / dsi->divider;

/* Round up the clk_set_rate() request slightly, since
* PLLD_DSI1 is an integer divider and its rate selection will
* never round up.
*/
adjusted_mode->clock = pixel_clock_hz / 1000 + 1;

/* Given the new pixel clock, adjust HFP to keep vrefresh the same. */
adjusted_mode->htotal = pixel_clock_hz / (mode->vrefresh * mode->vtotal);
adjusted_mode->hsync_end += adjusted_mode->htotal - mode->htotal;
adjusted_mode->hsync_start += adjusted_mode->htotal - mode->htotal;

return true;
}

static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)
{
struct drm_display_mode *mode = &encoder->crtc->mode;
struct drm_display_mode *mode = &encoder->crtc->state->adjusted_mode;
struct vc4_dsi_encoder *vc4_encoder = to_vc4_dsi_encoder(encoder);
struct vc4_dsi *dsi = vc4_encoder->dsi;
struct device *dev = &dsi->pdev->dev;
u32 format = 0, divider = 0;
bool debug_dump_regs = false;
unsigned long hs_clock;
u32 ui_ns;
Expand Down Expand Up @@ -940,26 +995,7 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)
vc4_dsi_dump_regs(dsi);
}

switch (dsi->format) {
case MIPI_DSI_FMT_RGB888:
format = DSI_PFORMAT_RGB888;
divider = 24 / dsi->lanes;
break;
case MIPI_DSI_FMT_RGB666:
format = DSI_PFORMAT_RGB666;
divider = 24 / dsi->lanes;
break;
case MIPI_DSI_FMT_RGB666_PACKED:
format = DSI_PFORMAT_RGB666_PACKED;
divider = 18 / dsi->lanes;
break;
case MIPI_DSI_FMT_RGB565:
format = DSI_PFORMAT_RGB565;
divider = 16 / dsi->lanes;
break;
}

phy_clock = pixel_clock_hz * divider;
phy_clock = pixel_clock_hz * dsi->divider;
ret = clk_set_rate(dsi->pll_phy_clock, phy_clock);
if (ret) {
dev_err(&dsi->pdev->dev,
Expand Down Expand Up @@ -1134,8 +1170,9 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)

if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO) {
DSI_PORT_WRITE(DISP0_CTRL,
VC4_SET_FIELD(divider, DSI_DISP0_PIX_CLK_DIV) |
VC4_SET_FIELD(format, DSI_DISP0_PFORMAT) |
VC4_SET_FIELD(dsi->divider,
DSI_DISP0_PIX_CLK_DIV) |
VC4_SET_FIELD(dsi->format, DSI_DISP0_PFORMAT) |
VC4_SET_FIELD(DSI_DISP0_LP_STOP_PERFRAME,
DSI_DISP0_LP_STOP_CTRL) |
DSI_DISP0_ST_END |
Expand Down Expand Up @@ -1347,9 +1384,31 @@ static int vc4_dsi_host_attach(struct mipi_dsi_host *host,

dsi->lanes = device->lanes;
dsi->channel = device->channel;
dsi->format = device->format;
dsi->mode_flags = device->mode_flags;

switch (device->format) {
case MIPI_DSI_FMT_RGB888:
dsi->format = DSI_PFORMAT_RGB888;
dsi->divider = 24 / dsi->lanes;
break;
case MIPI_DSI_FMT_RGB666:
dsi->format = DSI_PFORMAT_RGB666;
dsi->divider = 24 / dsi->lanes;
break;
case MIPI_DSI_FMT_RGB666_PACKED:
dsi->format = DSI_PFORMAT_RGB666_PACKED;
dsi->divider = 18 / dsi->lanes;
break;
case MIPI_DSI_FMT_RGB565:
dsi->format = DSI_PFORMAT_RGB565;
dsi->divider = 16 / dsi->lanes;
break;
default:
dev_err(&dsi->pdev->dev, "Unknown DSI format: %d.\n",
dsi->format);
return 0;
}

if (!(dsi->mode_flags & MIPI_DSI_MODE_VIDEO)) {
dev_err(&dsi->pdev->dev,
"Only VIDEO mode panels supported currently.\n");
Expand Down Expand Up @@ -1397,6 +1456,7 @@ static const struct mipi_dsi_host_ops vc4_dsi_host_ops = {
static const struct drm_encoder_helper_funcs vc4_dsi_encoder_helper_funcs = {
.disable = vc4_dsi_encoder_disable,
.enable = vc4_dsi_encoder_enable,
.mode_fixup = vc4_dsi_encoder_mode_fixup,
};

static const struct of_device_id vc4_dsi_dt_match[] = {
Expand Down

0 comments on commit 86c1b9e

Please sign in to comment.