On 9/16/18 4:55 AM, r yang wrote:
On Fri, Sep 14, 2018 at 01:58:57PM +0300, Dmitry Osipenko wrote:
On 9/9/18 6:22 AM, r yang wrote:
On Fri, Sep 07, 2018 at 09:01:14PM +0300, Dmitry Osipenko wrote:
On 9/5/18 12:37 PM, Peter De Schrijver wrote:
Sorry, I had it wrong. It is 76Mhz. Not 72Mhz.
I have spent a great deal of time trying to find alternate clock
configuration for the display panel that can work. The only ways are:
- Run disp1 on pll_d
- Dedicate pll_c to disp1. Move all gpu clocks and sclk/hclk/ahbdma to pll_m.
PLL_M is kinda reserved for the memory, hence its rate can't be changed.
I think the best solution here would be to make use of the
'Assigned clock parents and rates' and rates feature to allow selecting the
display clock sources on a per board basis.
Looks like it works, here the device-tree that I used:
host1x@50000000 {
dc@54200000 {
clocks = <&tegra_car TEGRA20_CLK_DISP1>,
<&tegra_car TEGRA20_CLK_PLL_C>;
/* Re-parent SCLK to P_OUT4 and set PLL_C to 586MHz */
assigned-clocks = <&tegra_car TEGRA20_CLK_SCLK>,
<&tegra_car TEGRA20_CLK_HCLK>,
<&tegra_car TEGRA20_CLK_PCLK>,
<&tegra_car TEGRA20_CLK_PLL_C>;
assigned-clock-rates = <216000000>, /* SCLK */
<216000000>, /* HCLK */
<54000000>, /* PCLK */
<586000000>; /* PLL_C */
assigned-clock-parents = <&tegra_car TEGRA20_CLK_PLL_P_OUT4>;
rgb {
status = "okay";
nvidia,panel = <&panel>;
};
};
hdmi@54280000 {
status = "okay";
vdd-supply = <&hdmi_vdd_reg>;
pll-supply = <&hdmi_pll_reg>;
nvidia,ddc-i2c-bus = <&hdmi_ddc>;
nvidia,hpd-gpio = <&gpio TEGRA_GPIO(N, 7)
GPIO_ACTIVE_HIGH>;
};
};
This configuration works. Using this feature doesn't require any
change to the display driver.
Thanks.
Nice! Though the pclk=0 still need to be fixed in the DRM driver. Peter
suggested earlier (on IRC) that rather than error'ing out on freq=0 in the
clk driver, the freq shall round up to the lowest possible value.
Makes sense since the round_rate documentation says it should return the
closest rate actually supported by the clock. Has anyone taken to making
this change?
I may take a closer look at it later this / next week.
I think the minimum rate can be derived based on the same pll constraints
used in the _calc_rate() function. I've tested it on pll_c and pll_d but
I'm not 100% certain about my method yet.
Feel free to send out RFC patch, it's always better to look at the actual code.
