drm/msm/dsi/phy: Do not overwite PHY_CMN_CLK_CFG1 when choosing bitclk source

PHY_CMN_CLK_CFG1 register has four fields being used in the driver: DSI
clock divider, source of bitclk and two for enabling the DSI PHY PLL
clocks.

dsi_7nm_set_usecase() sets only the source of bitclk, so should leave
all other bits untouched.  Use newly introduced
dsi_pll_cmn_clk_cfg1_update() to update respective bits without
overwriting the rest.

While shuffling the code, define and use PHY_CMN_CLK_CFG1 bitfields to
make the code more readable and obvious.

Fixes: 1ef7c99 ("drm/msm/dsi: add support for 7nm DSI PHY/PLL")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/637380/
Link: https://lore.kernel.org/r/20250214-drm-msm-phy-pll-cfg-reg-v3-3-0943b850722c@linaro.org
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

Author: krzk

drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c

@@ -617,7 +617,6 @@ static int dsi_7nm_pll_restore_state(struct msm_dsi_phy *phy)
 static int dsi_7nm_set_usecase(struct msm_dsi_phy *phy)
 {
 	struct dsi_pll_7nm *pll_7nm = to_pll_7nm(phy->vco_hw);
-	void __iomem *base = phy->base;
 	u32 data = 0x0;	/* internal PLL */
 
 	DBG("DSI PLL%d", pll_7nm->phy->id);
@@ -636,7 +635,8 @@ static int dsi_7nm_set_usecase(struct msm_dsi_phy *phy)
 	}
 
 	/* set PLL src */
-	writel(data << 2, base + REG_DSI_7nm_PHY_CMN_CLK_CFG1);
+	dsi_pll_cmn_clk_cfg1_update(pll_7nm, DSI_7nm_PHY_CMN_CLK_CFG1_BITCLK_SEL__MASK,
+				    DSI_7nm_PHY_CMN_CLK_CFG1_BITCLK_SEL(data));
 
 	return 0;
 }

drivers/gpu/drm/msm/registers/display/dsi_phy_7nm.xml

@@ -16,6 +16,7 @@ xsi:schemaLocation="https://gitlab.freedesktop.org/freedreno/ rules-fd.xsd">
 	<reg32 offset="0x00014" name="CLK_CFG1">
 		<bitfield name="CLK_EN" pos="5" type="boolean"/>
 		<bitfield name="CLK_EN_SEL" pos="4" type="boolean"/>
+		<bitfield name="BITCLK_SEL" low="2" high="3" type="uint"/>
 	</reg32>
 	<reg32 offset="0x00018" name="GLBL_CTRL"/>
 	<reg32 offset="0x0001c" name="RBUF_CTRL"/>