linux-kernel - Re: [PATCH 5/9] drm/meson: dw-hdmi: split resets out of hw init.

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Message-ID: <1ja5hozqkd.fsf@starbuckisacylon.baylibre.com>
Date: Wed, 07 Aug 2024 10:26:42 +0200
From: Jerome Brunet <jbrunet@...libre.com>
To: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>,  Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>,  Maxime Ripard <mripard@...nel.org>,
  Thomas Zimmermann <tzimmermann@...e.de>,  David Airlie
 <airlied@...il.com>,  Daniel Vetter <daniel@...ll.ch>,  Kevin Hilman
 <khilman@...libre.com>,  dri-devel@...ts.freedesktop.org,
  linux-amlogic@...ts.infradead.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/9] drm/meson: dw-hdmi: split resets out of hw init.

On Tue 06 Aug 2024 at 22:49, Martin Blumenstingl <martin.blumenstingl@...glemail.com> wrote:

> Hi Jerome,
>
> On Tue, Jul 30, 2024 at 2:50 PM Jerome Brunet <jbrunet@...libre.com> wrote:
>>
>> This prepares the migration to regmap usage.
>>
>> To properly setup regmap, the APB needs to be in working order.
>> This is easier handled if the resets are not mixed with hw init.
>>
>> More checks are required to determine if the resets are needed
>> on resume or not. Add a note for this.
>>
>> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
>> ---
>>  drivers/gpu/drm/meson/meson_dw_hdmi.c | 14 +++++++++-----
>>  1 file changed, 9 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
>> index 5cd3264ab874..47aa3e184e98 100644
>> --- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
>> +++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
>> @@ -581,11 +581,6 @@ static void meson_dw_hdmi_init(struct meson_dw_hdmi *meson_dw_hdmi)
>>         /* Bring HDMITX MEM output of power down */
>>         regmap_update_bits(priv->hhi, HHI_MEM_PD_REG0, 0xff << 8, 0);
>>
>> -       /* Reset HDMITX APB & TX & PHY */
>> -       reset_control_reset(meson_dw_hdmi->hdmitx_apb);
>> -       reset_control_reset(meson_dw_hdmi->hdmitx_ctrl);
>> -       reset_control_reset(meson_dw_hdmi->hdmitx_phy);
>> -
>>         /* Enable APB3 fail on error */
>>         if (!meson_vpu_is_compatible(priv, VPU_COMPATIBLE_G12A)) {
>>                 writel_bits_relaxed(BIT(15), BIT(15),
>> @@ -675,6 +670,10 @@ static int meson_dw_hdmi_bind(struct device *dev, struct device *master,
>>                 return PTR_ERR(meson_dw_hdmi->hdmitx_phy);
>>         }
>>
>> +       reset_control_reset(meson_dw_hdmi->hdmitx_apb);
>> +       reset_control_reset(meson_dw_hdmi->hdmitx_ctrl);
>> +       reset_control_reset(meson_dw_hdmi->hdmitx_phy);
> The old out of tree vendor driver [0] enables the "isfr" and "iahb"
> (in P_HHI_HDMI_CLK_CNTL and P_HHI_GCLK_MPEG2) clocks before triggering
> the resets.
> Previously meson_dw_hdmi's behavior was identical as it enabled the
> clocks in meson_dw_hdmi_bind() and only later triggered the resets.
>
> I'm totally fine with moving the resets to meson_dw_hdmi_bind() but I
> think it should happen after devm_clk_bulk_get_all_enable() has been
> called (to keep the order and thus avoid side-effects that we don't
> know about yet).

Good point.

I was also thinking about squashing this with the regmap patch.
I've split it apart for v1 to make things a bit more clear but it only
really makes sense with the regmap conversion. 

>
> Also out of curiosity: are you planning to convert the driver to use
> devm_reset_control_bulk_get_exclusive()?
>

It's been a while this I've done that. I remember I thought about it.
I think it was a bit more difficult to use that clocks. I was looking at
making the driver a bit more clean and simple. It was not really helping
to move it in that direction IIRC.

>
> Best regards,
> Martin
>
>
> [0] https://github.com/endlessm/linux-s905x/blob/master/drivers/amlogic/hdmi/hdmi_tx_20/hw/hdmi_tx_hw.c#L470

-- 
Jerome