diff mbox

clk: imx: clk-imx6ul: allow lcdif_pre_sel to change parent rate

Message ID 20171012132935.3508-1-p.zabel@pengutronix.de (mailing list archive)
State New, archived
Headers show

Commit Message

Philipp Zabel Oct. 12, 2017, 1:29 p.m. UTC
Allowing the lcdif_pre_sel to propagate rate changes to its parent PLL
allows more fine grained control over the LCDIF pixel clock rate.

For example, the Innovision AT043TN24 LCD panel described in the
imx6ul-14x14-evk device tree requires a 9 MHz pixel clock.
Before this patch, the lcdif_pre_sel clock rate is fixed, and just
setting the lcdif_pred and lcdif_podf dividers only allows to get as
close as about 8.44 MHz:

    pll3                                  1            1   480000000 0 0
       pll3_bypass                        1            1   480000000 0 0
	  pll3_usb_otg                    1            1   480000000 0 0
	     pll3_pfd1_540m               1            1   540000000 0 0
		lcdif_pre_sel             1            1   540000000 0 0
		   lcdif_pred             1            1    67500000 0 0
		      lcdif_podf           1            1     8437500 0 0
			 lcdif_pix           1            1     8437500 0 0

Once lcdif_pre_sel is allowed to propagate rate requests to its parent,
the actual pixel clock matches the requested value:

    pll3                                  1            1   480000000 0 0
       pll3_bypass                        1            1   480000000 0 0
	  pll3_usb_otg                    1            1   480000000 0 0
	     pll3_pfd1_540m               1            1   288000000 0 0
		lcdif_pre_sel             1            1   288000000 0 0
		   lcdif_pred             1            1    36000000 0 0
		      lcdif_podf           1            1     9000000 0 0
                         lcdif_pix           1            1     9000000 0 0

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 drivers/clk/imx/clk-imx6ul.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Fabio Estevam Oct. 12, 2017, 1:39 p.m. UTC | #1
On Thu, Oct 12, 2017 at 10:29 AM, Philipp Zabel <p.zabel@pengutronix.de> wrote:
> Allowing the lcdif_pre_sel to propagate rate changes to its parent PLL
> allows more fine grained control over the LCDIF pixel clock rate.
>
> For example, the Innovision AT043TN24 LCD panel described in the
> imx6ul-14x14-evk device tree requires a 9 MHz pixel clock.
> Before this patch, the lcdif_pre_sel clock rate is fixed, and just
> setting the lcdif_pred and lcdif_podf dividers only allows to get as
> close as about 8.44 MHz:
>
>     pll3                                  1            1   480000000 0 0
>        pll3_bypass                        1            1   480000000 0 0
>           pll3_usb_otg                    1            1   480000000 0 0
>              pll3_pfd1_540m               1            1   540000000 0 0
>                 lcdif_pre_sel             1            1   540000000 0 0
>                    lcdif_pred             1            1    67500000 0 0
>                       lcdif_podf           1            1     8437500 0 0
>                          lcdif_pix           1            1     8437500 0 0
>
> Once lcdif_pre_sel is allowed to propagate rate requests to its parent,
> the actual pixel clock matches the requested value:
>
>     pll3                                  1            1   480000000 0 0
>        pll3_bypass                        1            1   480000000 0 0
>           pll3_usb_otg                    1            1   480000000 0 0
>              pll3_pfd1_540m               1            1   288000000 0 0
>                 lcdif_pre_sel             1            1   288000000 0 0
>                    lcdif_pred             1            1    36000000 0 0
>                       lcdif_podf           1            1     9000000 0 0
>                          lcdif_pix           1            1     9000000 0 0
>
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

Yes, much better precision now, thanks:

Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Stephen Boyd Nov. 2, 2017, 7:25 a.m. UTC | #2
On 10/12, Philipp Zabel wrote:
> Allowing the lcdif_pre_sel to propagate rate changes to its parent PLL
> allows more fine grained control over the LCDIF pixel clock rate.
> 
> For example, the Innovision AT043TN24 LCD panel described in the
> imx6ul-14x14-evk device tree requires a 9 MHz pixel clock.
> Before this patch, the lcdif_pre_sel clock rate is fixed, and just
> setting the lcdif_pred and lcdif_podf dividers only allows to get as
> close as about 8.44 MHz:
> 
>     pll3                                  1            1   480000000 0 0
>        pll3_bypass                        1            1   480000000 0 0
> 	  pll3_usb_otg                    1            1   480000000 0 0
> 	     pll3_pfd1_540m               1            1   540000000 0 0
> 		lcdif_pre_sel             1            1   540000000 0 0
> 		   lcdif_pred             1            1    67500000 0 0
> 		      lcdif_podf           1            1     8437500 0 0
> 			 lcdif_pix           1            1     8437500 0 0
> 
> Once lcdif_pre_sel is allowed to propagate rate requests to its parent,
> the actual pixel clock matches the requested value:
> 
>     pll3                                  1            1   480000000 0 0
>        pll3_bypass                        1            1   480000000 0 0
> 	  pll3_usb_otg                    1            1   480000000 0 0
> 	     pll3_pfd1_540m               1            1   288000000 0 0
> 		lcdif_pre_sel             1            1   288000000 0 0
> 		   lcdif_pred             1            1    36000000 0 0
> 		      lcdif_podf           1            1     9000000 0 0
>                          lcdif_pix           1            1     9000000 0 0
> 
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> ---

Applied to clk-next
diff mbox

Patch

diff --git a/drivers/clk/imx/clk-imx6ul.c b/drivers/clk/imx/clk-imx6ul.c
index 5e8c18afce9ad..85c1181644697 100644
--- a/drivers/clk/imx/clk-imx6ul.c
+++ b/drivers/clk/imx/clk-imx6ul.c
@@ -267,7 +267,7 @@  static void __init imx6ul_clocks_init(struct device_node *ccm_node)
 		clks[IMX6ULL_CLK_EPDC_SEL]	  = imx_clk_mux("epdc_sel",	base + 0x34, 9, 3, epdc_sels, ARRAY_SIZE(epdc_sels));
 	}
 	clks[IMX6UL_CLK_ECSPI_SEL]	  = imx_clk_mux("ecspi_sel",	base + 0x38, 18, 1, ecspi_sels, ARRAY_SIZE(ecspi_sels));
-	clks[IMX6UL_CLK_LCDIF_PRE_SEL]	  = imx_clk_mux("lcdif_pre_sel", base + 0x38, 15, 3, lcdif_pre_sels, ARRAY_SIZE(lcdif_pre_sels));
+	clks[IMX6UL_CLK_LCDIF_PRE_SEL]	  = imx_clk_mux_flags("lcdif_pre_sel", base + 0x38, 15, 3, lcdif_pre_sels, ARRAY_SIZE(lcdif_pre_sels), CLK_SET_RATE_PARENT);
 	clks[IMX6UL_CLK_LCDIF_SEL]	  = imx_clk_mux("lcdif_sel",	base + 0x38, 9, 3, lcdif_sels, ARRAY_SIZE(lcdif_sels));
 
 	clks[IMX6UL_CLK_LDB_DI0_DIV_SEL]  = imx_clk_mux("ldb_di0", base + 0x20, 10, 1, ldb_di0_div_sels, ARRAY_SIZE(ldb_di0_div_sels));