Re: [PATCH v2 RESEND 2/3] mfd: atmel-hlcdc: fetch LVDS PLL clock for LVDS display

Hi Lee,

On 06/11/25 6:32 pm, Lee Jones wrote:

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On Wed, 22 Oct 2025, Manikandan Muralidharan wrote:

quoted

The XLCDC IP supports parallel RGB, MIPI DSI and LVDS Display.
The LCD Generic clock (sys_clk) is used for Parallel RGB and MIPI
displays, while the LVDS PLL clock (lvds_pll_clk) is used for LVDS
displays.Since both the clocks cannot co-exist together in the DT
for a given display, this patch first attempts to retrieve sys_clk
If that fails,it then tries to acquire lvds_pll_clk.

Signed-off-by: Manikandan Muralidharan <manikandan.m@microchip.com>
Signed-off-by: Dharma Balasubiramani <dharma.b@microchip.com>
---
changes in v2:
- Rephrase the comments, commit message and err logs
- Replace dev_err wwith dev_warn
- Remove Initializing sys_clk and lvds_pll_clk to NULL post
devm_kzalloc() call

---
  drivers/mfd/atmel-hlcdc.c       | 16 ++++++++++++++--
  include/linux/mfd/atmel-hlcdc.h |  1 +
  2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/atmel-hlcdc.c b/drivers/mfd/atmel-hlcdc.c
index 4c4e35d404f3..f680392b01ba 100644
--- a/drivers/mfd/atmel-hlcdc.c
+++ b/drivers/mfd/atmel-hlcdc.c

@@ -108,10 +108,22 @@ static int atmel_hlcdc_probe(struct platform_device *pdev)
               return PTR_ERR(hlcdc->periph_clk);
       }

+     /*
+      * Retrieve any one of the Main clk required by the LCD to operate:
+      *
+      * LCDC Generic Clock (sys_clk) - Parallel RGB and MIPI displays,
+      * LVDS PLL (lvds_pll_clk)      - LVDS display
+      */
       hlcdc->sys_clk = devm_clk_get(dev, "sys_clk");
       if (IS_ERR(hlcdc->sys_clk)) {
-             dev_err(dev, "failed to get system clock\n");
-             return PTR_ERR(hlcdc->sys_clk);
+             dev_warn(dev,
+                      "failed to get LCDC generic clock, trying for LVDS PLL clock instead\n");

Does the user really care which clock they use?

Can this just happen silently instead?

quoted

+             hlcdc->lvds_pll_clk = devm_clk_get(dev, "lvds_pll_clk");
+             if (IS_ERR(hlcdc->lvds_pll_clk)) {
+                     dev_err(dev, "failed to get LVDS PLL clock\n");

Failed to obtain both the LCDC (generic) and LVDS PLL clocks

Thankyou, I will make sure v3 addresses these comments.

quoted

+                     return PTR_ERR(hlcdc->lvds_pll_clk);
+             }
       }

       hlcdc->slow_clk = devm_clk_get(dev, "slow_clk");

diff --git a/include/linux/mfd/atmel-hlcdc.h b/include/linux/mfd/atmel-hlcdc.h
index 80d675a03b39..07c2081867fd 100644
--- a/include/linux/mfd/atmel-hlcdc.h
+++ b/include/linux/mfd/atmel-hlcdc.h

@@ -75,6 +75,7 @@
   */
  struct atmel_hlcdc {
       struct regmap *regmap;
+     struct clk *lvds_pll_clk;
       struct clk *periph_clk;
       struct clk *sys_clk;
       struct clk *slow_clk;
--

2.25.1

--
Lee Jones [李琼斯]

-- 
Thanks and Regards,
Manikandan M.