linux-kernel - Re: [PATCH v1] drm/bridge: tc358768: Fix DSI command tx

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Message-ID: <20241114095754.GA23530@francesco-nb>
Date: Thu, 14 Nov 2024 10:57:54 +0100
From: Francesco Dolcini <francesco@...cini.it>
To: Neil Armstrong <neil.armstrong@...aro.org>
Cc: Francesco Dolcini <francesco@...cini.it>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Robert Foss <rfoss@...nel.org>,
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
	Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Francesco Dolcini <francesco.dolcini@...adex.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v1] drm/bridge: tc358768: Fix DSI command tx

Hello Neil,

On Wed, Oct 23, 2024 at 10:03:20AM +0200, Neil Armstrong wrote:
> On 26/09/2024 16:12, Francesco Dolcini wrote:
> > From: Francesco Dolcini <francesco.dolcini@...adex.com>
> > 
> > Wait for the command transmission to be completed in the DSI transfer
> > function polling for the dc_start bit to go back to idle state after the
> > transmission is started.
> > 
> > This is documented in the datasheet and failures to do so lead to
> > commands corruption.
> > 
> > Fixes: ff1ca6397b1d ("drm/bridge: Add tc358768 driver")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Francesco Dolcini <francesco.dolcini@...adex.com>
> > ---
> >   drivers/gpu/drm/bridge/tc358768.c | 21 +++++++++++++++++++--
> >   1 file changed, 19 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c
> > index 0e8813278a2f..bb1750a3dab0 100644
> > --- a/drivers/gpu/drm/bridge/tc358768.c
> > +++ b/drivers/gpu/drm/bridge/tc358768.c
> > @@ -125,6 +125,9 @@
> >   #define TC358768_DSI_CONFW_MODE_CLR	(6 << 29)
> >   #define TC358768_DSI_CONFW_ADDR_DSI_CONTROL	(0x3 << 24)
> > +/* TC358768_DSICMD_TX (0x0600) register */
> > +#define TC358768_DSI_CMDTX_DC_START	BIT(0)
> > +
> >   static const char * const tc358768_supplies[] = {
> >   	"vddc", "vddmipi", "vddio"
> >   };
> > @@ -229,6 +232,21 @@ static void tc358768_update_bits(struct tc358768_priv *priv, u32 reg, u32 mask,
> >   		tc358768_write(priv, reg, tmp);
> >   }
> > +static void tc358768_dsicmd_tx(struct tc358768_priv *priv)
> > +{
> > +	u32 val;
> > +
> > +	/* start transfer */
> > +	tc358768_write(priv, TC358768_DSICMD_TX, TC358768_DSI_CMDTX_DC_START);
> > +	if (priv->error)
> > +		return;
> > +
> > +	/* wait transfer completion */
> > +	priv->error = regmap_read_poll_timeout(priv->regmap, TC358768_DSICMD_TX, val,
> > +					       (val & TC358768_DSI_CMDTX_DC_START) == 0,
> > +					       100, 100000);
> > +}
> > +
> >   static int tc358768_sw_reset(struct tc358768_priv *priv)
> >   {
> >   	/* Assert Reset */
> > @@ -516,8 +534,7 @@ static ssize_t tc358768_dsi_host_transfer(struct mipi_dsi_host *host,
> >   		}
> >   	}
> > -	/* start transfer */
> > -	tc358768_write(priv, TC358768_DSICMD_TX, 1);
> > +	tc358768_dsicmd_tx(priv);
> >   	ret = tc358768_clear_error(priv);
> >   	if (ret)
> 
> Look good, I'll leave it here a few days if someone has comments

Just a gently reminder, thanks

> Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>

Francesco