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Message-ID: <CAMty3ZDCCRXLvHaoW=8gqq+3B0j4uQvAk72YjXKr=cxuf7GAkg@mail.gmail.com>
Date: Thu, 25 Nov 2021 11:12:17 +0530
From: Jagan Teki <jagan@...rulasolutions.com>
To: Adam Ford <aford173@...il.com>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>,
arm-soc <linux-arm-kernel@...ts.infradead.org>,
Tim Harvey <tharvey@...eworks.com>,
Schrempf Frieder <frieder.schrempf@...tron.de>,
linux-media <linux-media@...r.kernel.org>,
Adam Ford-BE <aford@...conembedded.com>,
cstevens@...conembedded.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 <devicetree@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 1/5] soc: imx: imx8m-blk-ctrl: Fix imx8mm mipi reset
On Tue, Nov 23, 2021 at 7:29 PM Adam Ford <aford173@...il.com> wrote:
>
> On Sun, Nov 21, 2021 at 4:25 PM Laurent Pinchart
> <laurent.pinchart@...asonboard.com> wrote:
> >
> > Hi Adam,
> >
> > 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 ?
>
> In some early attempts to implement the blk-ctrl driver, there was an
> attempt to enable a reset controller, but it caused some hanging and
> issues with suspend-resume due to chicken-egg issues where some items
> were coming up in the wrong order. I think the decision was made to
> make the resets part of the power domain so it's very clear that the
> order of operations. Lucas might be able to elaborate more on this.
I think supporting via phy driver make sense to me since this resent
is DPHY specific and nothing related to blk-ctrl.
>
> If bits 16 and 17 can act independently and bit 16 only impacts the
> CSI and doesn't require bit 17, it seems reasonable to me to have the
> power-domain part of the CSI, since this would only be enabled when
> the CSI is active. The power domain is idled when the CSI is idled
> which would effectively place the phy in and out of reset only
> depending on the state of the CSI. I am guessing this reset bit
> should be assigned to DISPBLK_PD_MIPI_CSI and not
> DISPBLK_PD_CSI_BRIDGE, but I can run some more tests.
>
> AFAIK, there is no phy driver for the CSI like there is the DSI, so
> adding that would require additional work to the CSI driver to work
> around this quirk. We don't have an acceptable DSI driver yet, so I'd
> like to push a V3 with just the corresponding bit enabled for MIPI_CSI
> after some testing. FWICT, NXP set both bits 16 and 17 in their ATF
> gpc code, and it never gets cleared, so I think having the bit set and
> cleared on demand is an improvement.
How about using the previous one that Marek sent. Add it via CSI
pipeline and i think it would directly.
https://www.spinics.net/lists/devicetree/msg381691.html
Jagan.
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