linux-kernel - Re: [PATCH 7/9] riscv: dts: spacemit: Add PWM14 backlight support for BPI-F3

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Message-ID: <cwbbq6pubksgpbloqdxspn7sr7tanbjdnbdobctayblpkahukp@zxypidw7a6un>
Date: Sat, 12 Apr 2025 06:54:57 +0800
From: Inochi Amaoto <inochiama@...il.com>
To: Guodong Xu <guodong@...cstar.com>, ukleinek@...nel.org, 
	robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu, alex@...ti.fr, 
	dlan@...too.org, p.zabel@...gutronix.de, drew@...7.com, inochiama@...il.com, 
	geert+renesas@...der.be, heylenay@....org, tglx@...utronix.de, hal.feng@...rfivetech.com, 
	unicorn_wang@...look.com, duje.mihanovic@...le.hr
Cc: elder@...cstar.com, linux-pwm@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	spacemit@...ts.linux.dev
Subject: Re: [PATCH 7/9] riscv: dts: spacemit: Add PWM14 backlight support
 for BPI-F3

On Fri, Apr 11, 2025 at 09:14:21PM +0800, Guodong Xu wrote:
> Add a PWM-based backlight node for the Banana Pi BPI-F3 board,
> using PWM14. The backlight is defined as a 'pwm-backlight' device with
> brightness levels and a default brightness setting. PWM14 is assigned
> a period length of 2000 nanoseconds.
> 
> This configuration was used to verify PWM driver changes, with PWM14
> tested and its waveform confirmed as correct.
> 
> The node status is set to "disabled", and should be enabled when the
> display driver is ready.
> 
> Signed-off-by: Guodong Xu <guodong@...cstar.com>
> ---
>  .../boot/dts/spacemit/k1-bananapi-f3.dts      | 32 +++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts b/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts
> index 816ef1bc358e..d04b57ddeb46 100644
> --- a/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts
> +++ b/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts
> @@ -28,6 +28,32 @@ led1 {
>  			default-state = "on";
>  		};
>  	};
> +
> +	pwm_bl: lcd_backlight {
> +		compatible = "pwm-backlight";
> +
> +		pwms = <&pwm14 2000>;

> +		brightness-levels = <
> +			0   40  40  40  40  40  40  40  40  40  40  40  40  40  40  40
> +			40  40  40  40  40  40  40  40  40  40  40  40  40  40  40  40
> +			40  40  40  40  40  40  40  40  40  41  42  43  44  45  46  47
> +			48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63
> +			64  65  66  67  68  69  70  71  72  73  74  75  76  77  78  79
> +			80  81  82  83  84  85  86  87  88  89  90  91  92  93  94  95
> +			96  97  98  99  100 101 102 103 104 105 106 107 108 109 110 111
> +			112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127
> +			128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143
> +			144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159
> +			160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175
> +			176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191
> +			192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207
> +			208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223
> +			224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239
> +			240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255
> +		>;

Can we simplify this level matrix? I see it is continous in most cases.

Regards,
Inochi