Re: [PATCH v12 16/18] drm: bridge: analogix/dp: expand the wait time for looking AUX CH reply flag

[Yakir Yang]

Hi Jingoo,

Okay, fine, I would drop this patch, until I found the the root cause.

- Yakir

On 12/23/2015 11:10 PM, Jingoo Han wrote:
> On Wednesday, December 23, 2015 9:51 PM, Yakir Yang wrote:
> > On Rockchip platform, sometimes driver would failed at reading EDID
> > message, and it's caused by the AUX reply flag wouldn't received under
> > the 100*10us wait time.
> The problem is specific for Rockchip platform.
> Also, 1 ms is long time.
> The best way is that your hardware engineers find the root cause.
> I cannot understand why your engineers cannot find the root cause. :-(
>
> > But after expand the wait time a little, the AUX reply flag would be
> > set, so maybe the wait time is a little critical. Besides the analogix
> > dp book haven't reminded the standard wait for looking AUX reply flag,
> > so I thought it's okay to expand the wait time.
> >
> > And the external wait time won't hurt Exynos DP too much, cause they
> > wouldn't meet this problem, then driver would received the reply command
> > very soon, so no more additional wait time would bring to Exynos platform.
> Then, when loop time happens on Exynos platform, it will take long time
> to return error.
>
> > Signed-off-by: Yakir Yang <ykk@xxxxxxxxxxxxxx>
> > ---
> > Changes in v12:
> > - Using another way to expand the AUX reply wait time (Jingoo)
> >
> > Changes in v11: None
> > Changes in v10: None
> > Changes in v9: None
> > Changes in v8: None
> > Changes in v7: None
> > Changes in v6: None
> > Changes in v5: None
> > Changes in v4: None
> > Changes in v3: None
> > Changes in v2: None
> >
> >   drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c | 10 ++++------
> >   1 file changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> > b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> > index cba3ffd..8687eea 100644
> > --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> > +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> > @@ -471,7 +471,7 @@ int analogix_dp_start_aux_transaction(struct analogix_dp_device *dp)
> >   {
> >   	int reg;
> >   	int retval = 0;
> > -	int timeout_loop = 0;
> > +	unsigned long timeout;
> >
> >   	/* Enable AUX CH operation */
> >   	reg = readl(dp->reg_base + ANALOGIX_DP_AUX_CH_CTL_2);
> > @@ -479,14 +479,12 @@ int analogix_dp_start_aux_transaction(struct analogix_dp_device *dp)
> >   	writel(reg, dp->reg_base + ANALOGIX_DP_AUX_CH_CTL_2);
> >
> >   	/* Is AUX CH command reply received? */
> > -	reg = readl(dp->reg_base + ANALOGIX_DP_INT_STA);
> > -	while (!(reg & RPLY_RECEIV)) {
> > -		timeout_loop++;
> > -		if (DP_TIMEOUT_LOOP_COUNT < timeout_loop) {
> > +	timeout = jiffies + msecs_to_jiffies(5);
> > +	while ((readl(dp->reg_base + ANALOGIX_DP_INT_STA) & RPLY_RECEIV) == 0) {
> > +		if (time_after(jiffies, timeout)) {
> >   			dev_err(dp->dev, "AUX CH command reply failed!\n");
> >   			return -ETIMEDOUT;
> >   		}
> > -		reg = readl(dp->reg_base + ANALOGIX_DP_INT_STA);
> Sorry, I don't like your patch.
>
> The problem happens because of Rockchip platform.
> So, you need to add workaround for only Rockchip platform.
>
> Just add new DT property and new variable for the value for wait time.
> When, the probe is called, new wait time value is read from Rockchip DT file.
> Then, the new wait time value can be written to the new variable.
>
>      new DT property: wait-time-aux
>      new variable: wait_time_aux
>
>
> If ( ) // New DT
>      wait_time_aux = New DT;
> else
>      wait_time_aux = 10;
>
>
> >   		usleep_range(10, 11);
> If there is NO  new wait time value from DT file, the default value '10' is
> used for sleep.
>
> But, if there is new wait time value from DT file, new wait time value
> can be used for sleep.
>
>                   usleep_range(dp->wait_time_aux, dp->wait_time_aux + 1);
>
> What I want to say is that there should be NO effect on Exynos platform,
> because of the hardware bug of Rockchip platform.
>
> Best regards,
> Jingoo Han
>
> >   	}
> >
> > --
> > 1.9.1


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