linux-kernel - Re: [PATCH V2 1/5] soc: imx: imx8m-blk-ctrl: Fix imx8mm mipi reset

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Date:   Mon, 22 Nov 2021 00:30:17 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Adam Ford <aford173@...il.com>
Cc:     linux-arm-kernel@...ts.infradead.org, tharvey@...eworks.com,
        frieder.schrempf@...tron.de, linux-media@...r.kernel.org,
        aford@...conembedded.com, cstevens@...conembedded.com,
        jagan@...rulasolutions.com, Rob Herring <robh+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Peng Fan <peng.fan@....com>,
        Lucas Stach <l.stach@...gutronix.de>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/5] soc: imx: imx8m-blk-ctrl: Fix imx8mm mipi reset

Hi Adam,

On Mon, Nov 22, 2021 at 12:25:31AM +0200, Laurent Pinchart wrote:
> On Sat, Nov 06, 2021 at 10:54:23AM -0500, Adam Ford wrote:
> > Most of the blk-ctrl reset bits are found in one register, however
> > there are two bits in offset 8 for pulling the MIPI DPHY out of reset
> > and these need to be set when IMX8MM_DISPBLK_PD_MIPI_CSI is brought
> > out of reset or the MIPI_CSI hangs.
> > 
> > Fixes: 926e57c065df ("soc: imx: imx8m-blk-ctrl: add DISP blk-ctrl")
> > Signed-off-by: Adam Ford <aford173@...il.com>
> > ---
> > 
> > V2:  Make a note that the extra register is only for Mini/Nano DISPLAY_BLK_CTRL
> >      Rename the new register to mipi_phy_rst_mask
> >      Encapsulate the edits to this register with an if-statement
> > 
> >  drivers/soc/imx/imx8m-blk-ctrl.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> > 
> > diff --git a/drivers/soc/imx/imx8m-blk-ctrl.c b/drivers/soc/imx/imx8m-blk-ctrl.c
> > index 519b3651d1d9..581eb4bc7f7d 100644
> > --- a/drivers/soc/imx/imx8m-blk-ctrl.c
> > +++ b/drivers/soc/imx/imx8m-blk-ctrl.c
> > @@ -17,6 +17,7 @@
> >  
> >  #define BLK_SFT_RSTN	0x0
> >  #define BLK_CLK_EN	0x4
> > +#define BLK_MIPI_RESET_DIV	0x8 /* Mini/Nano DISPLAY_BLK_CTRL only */
> >  
> >  struct imx8m_blk_ctrl_domain;
> >  
> > @@ -36,6 +37,15 @@ struct imx8m_blk_ctrl_domain_data {
> >  	const char *gpc_name;
> >  	u32 rst_mask;
> >  	u32 clk_mask;
> > +
> > +	/*
> > +	 * i.MX8M Mini and Nano have a third DISPLAY_BLK_CTRL register
> > +	 * which is used to control the reset for the MIPI Phy.
> > +	 * Since it's only present in certain circumstances,
> > +	 * an if-statement should be used before setting and clearing this
> > +	 * register.
> > +	 */
> > +	u32 mipi_phy_rst_mask;
> >  };
> >  
> >  #define DOMAIN_MAX_CLKS 3
> > @@ -78,6 +88,8 @@ static int imx8m_blk_ctrl_power_on(struct generic_pm_domain *genpd)
> >  
> >  	/* put devices into reset */
> >  	regmap_clear_bits(bc->regmap, BLK_SFT_RSTN, data->rst_mask);
> > +	if (data->mipi_phy_rst_mask)
> > +		regmap_clear_bits(bc->regmap, BLK_MIPI_RESET_DIV, data->mipi_phy_rst_mask);
> >  
> >  	/* enable upstream and blk-ctrl clocks to allow reset to propagate */
> >  	ret = clk_bulk_prepare_enable(data->num_clks, domain->clks);
> > @@ -99,6 +111,8 @@ static int imx8m_blk_ctrl_power_on(struct generic_pm_domain *genpd)
> >  
> >  	/* release reset */
> >  	regmap_set_bits(bc->regmap, BLK_SFT_RSTN, data->rst_mask);
> > +	if (data->mipi_phy_rst_mask)
> > +		regmap_set_bits(bc->regmap, BLK_MIPI_RESET_DIV, data->mipi_phy_rst_mask);
> >  
> >  	/* disable upstream clocks */
> >  	clk_bulk_disable_unprepare(data->num_clks, domain->clks);
> > @@ -120,6 +134,9 @@ static int imx8m_blk_ctrl_power_off(struct generic_pm_domain *genpd)
> >  	struct imx8m_blk_ctrl *bc = domain->bc;
> >  
> >  	/* put devices into reset and disable clocks */
> > +	if (data->mipi_phy_rst_mask)
> > +		regmap_clear_bits(bc->regmap, BLK_MIPI_RESET_DIV, data->mipi_phy_rst_mask);
> > +
> 
> Is it the best option to enable/disable both the master and slave MIPI
> DPHY, regardless of whether they're used or not ? Or would it be better
> to implement a reset controller to expose the two resets independently,
> and acquire them from the corresponding display and camera drivers ?

And I've now seen this has been raised by Jagan. I'll reply to that
e-mail.

> >  	regmap_clear_bits(bc->regmap, BLK_SFT_RSTN, data->rst_mask);
> >  	regmap_clear_bits(bc->regmap, BLK_CLK_EN, data->clk_mask);
> >  
> > @@ -488,6 +505,7 @@ static const struct imx8m_blk_ctrl_domain_data imx8mm_disp_blk_ctl_domain_data[]
> >  		.gpc_name = "mipi-csi",
> >  		.rst_mask = BIT(3) | BIT(4),
> >  		.clk_mask = BIT(10) | BIT(11),
> > +		.mipi_phy_rst_mask = BIT(16) | BIT(17),
> >  	},
> >  };
> >  

-- 
Regards,

Laurent Pinchart