| Message ID | 20161116093732.12828-2-wens@csie.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Nov 16, 2016 at 05:37:32PM +0800, Chen-Yu Tsai wrote: > If we attempt to read/write the TCON registers before the bus clock > is enabled, those accesses get ignored. > > In practice this almost never occurs because U-boot had already enabled > the bus clock as part of its firmware provided framebuffer (simplefb). > > Fixes: 9026e0d122ac ("drm: Add Allwinner A10 Display Engine support") > Signed-off-by: Chen-Yu Tsai <wens@csie.org> > --- > > I was looking around the DRM driver and noticed this sequence was off. > > --- > drivers/gpu/drm/sun4i/sun4i_tcon.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c > index c6afb2448655..8c2db65ea229 100644 > --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c > +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c > @@ -506,16 +506,16 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master, > return ret; > } > > - ret = sun4i_tcon_init_regmap(dev, tcon); > + ret = sun4i_tcon_init_clocks(dev, tcon); > if (ret) { > - dev_err(dev, "Couldn't init our TCON regmap\n"); > + dev_err(dev, "Couldn't init our TCON clocks\n"); > goto err_assert_reset; > } > > - ret = sun4i_tcon_init_clocks(dev, tcon); > + ret = sun4i_tcon_init_regmap(dev, tcon); > if (ret) { > - dev_err(dev, "Couldn't init our TCON clocks\n"); > - goto err_assert_reset; > + dev_err(dev, "Couldn't init our TCON regmap\n"); > + goto err_free_clocks; > } That won't work either. sun4i_tcon_init_clocks requires the regmap to be enabled before it calls sun4i_dclk_create. Maybe we should just move that call outside of sun4i_tcon_init_clocks and put it directly into the bind then. Maxime
On Fri, Nov 18, 2016 at 3:05 AM, Maxime Ripard <maxime.ripard@free-electrons.com> wrote: > On Wed, Nov 16, 2016 at 05:37:32PM +0800, Chen-Yu Tsai wrote: >> If we attempt to read/write the TCON registers before the bus clock >> is enabled, those accesses get ignored. >> >> In practice this almost never occurs because U-boot had already enabled >> the bus clock as part of its firmware provided framebuffer (simplefb). >> >> Fixes: 9026e0d122ac ("drm: Add Allwinner A10 Display Engine support") >> Signed-off-by: Chen-Yu Tsai <wens@csie.org> >> --- >> >> I was looking around the DRM driver and noticed this sequence was off. >> >> --- >> drivers/gpu/drm/sun4i/sun4i_tcon.c | 10 +++++----- >> 1 file changed, 5 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c >> index c6afb2448655..8c2db65ea229 100644 >> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c >> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c >> @@ -506,16 +506,16 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master, >> return ret; >> } >> >> - ret = sun4i_tcon_init_regmap(dev, tcon); >> + ret = sun4i_tcon_init_clocks(dev, tcon); >> if (ret) { >> - dev_err(dev, "Couldn't init our TCON regmap\n"); >> + dev_err(dev, "Couldn't init our TCON clocks\n"); >> goto err_assert_reset; >> } >> >> - ret = sun4i_tcon_init_clocks(dev, tcon); >> + ret = sun4i_tcon_init_regmap(dev, tcon); >> if (ret) { >> - dev_err(dev, "Couldn't init our TCON clocks\n"); >> - goto err_assert_reset; >> + dev_err(dev, "Couldn't init our TCON regmap\n"); >> + goto err_free_clocks; >> } > > That won't work either. sun4i_tcon_init_clocks requires the regmap to > be enabled before it calls sun4i_dclk_create. > > Maybe we should just move that call outside of sun4i_tcon_init_clocks > and put it directly into the bind then. That makes sense. I'll send a v2. ChenYu
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c index c6afb2448655..8c2db65ea229 100644 --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c @@ -506,16 +506,16 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master, return ret; } - ret = sun4i_tcon_init_regmap(dev, tcon); + ret = sun4i_tcon_init_clocks(dev, tcon); if (ret) { - dev_err(dev, "Couldn't init our TCON regmap\n"); + dev_err(dev, "Couldn't init our TCON clocks\n"); goto err_assert_reset; } - ret = sun4i_tcon_init_clocks(dev, tcon); + ret = sun4i_tcon_init_regmap(dev, tcon); if (ret) { - dev_err(dev, "Couldn't init our TCON clocks\n"); - goto err_assert_reset; + dev_err(dev, "Couldn't init our TCON regmap\n"); + goto err_free_clocks; } ret = sun4i_tcon_init_irq(dev, tcon);
If we attempt to read/write the TCON registers before the bus clock is enabled, those accesses get ignored. In practice this almost never occurs because U-boot had already enabled the bus clock as part of its firmware provided framebuffer (simplefb). Fixes: 9026e0d122ac ("drm: Add Allwinner A10 Display Engine support") Signed-off-by: Chen-Yu Tsai <wens@csie.org> --- I was looking around the DRM driver and noticed this sequence was off. --- drivers/gpu/drm/sun4i/sun4i_tcon.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)