From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0D122C433EF for ; Mon, 25 Apr 2022 18:20:50 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id D9D3210E06E; Mon, 25 Apr 2022 18:20:48 +0000 (UTC) Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0B22410E06E; Mon, 25 Apr 2022 18:20:48 +0000 (UTC) Received: from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi [62.78.145.57]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 50128496; Mon, 25 Apr 2022 20:20:46 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1650910846; bh=40BJ2ulQyTcKJv6ZrNDl5oAAImwopfC+JsH7W6yD3QU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=f8NYudD1sb6B9xSfeECWuRRMkDdWhd8BGSdGfwow9oHJzt7IaHAF+hTcL6duduBW7 CV3zZs+7jU8j9H5uoKBlEgFl3ttfoJKg48FzKbsDlR8KeHRSplq26Tt8l8HF8mO5e9 SBLKfv4wRVl/L2PNxU/NLrxubFLg08ax0FdR0ilQ= Date: Mon, 25 Apr 2022 21:20:46 +0300 From: Laurent Pinchart To: Abhinav Kumar Subject: Re: [Freedreno] [PATCH v4 03/20] drm: allow real encoder to be passed for drm_writeback_connector Message-ID: References: <1650668815-7048-1-git-send-email-quic_abhinavk@quicinc.com> <1650668815-7048-4-git-send-email-quic_abhinavk@quicinc.com> <36c5e99b-3df6-88b3-a567-f24ca249d028@quicinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <36c5e99b-3df6-88b3-a567-f24ca249d028@quicinc.com> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: markyacoub@chromium.org, liviu.dudau@arm.com, dri-devel@lists.freedesktop.org, swboyd@chromium.org, seanpaul@chromium.org, Dmitry Baryshkov , quic_jesszhan@quicinc.com, quic_aravindh@quicinc.com, freedreno@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Mon, Apr 25, 2022 at 10:48:07AM -0700, Abhinav Kumar wrote: > On 4/25/2022 10:32 AM, Laurent Pinchart wrote: > > On Mon, Apr 25, 2022 at 01:50:43PM +0300, Dmitry Baryshkov wrote: > >> On Sun, 24 Apr 2022 at 22:59, Laurent Pinchart wrote: > >>> On Sun, Apr 24, 2022 at 11:23:20AM -0700, Abhinav Kumar wrote: > >>>> On 4/24/2022 11:12 AM, Abhinav Kumar wrote: > >>>>> On 4/24/2022 7:50 AM, Laurent Pinchart wrote: > >>>>>> On Fri, Apr 22, 2022 at 04:06:38PM -0700, Abhinav Kumar wrote: > >>>>>>> For some vendor driver implementations, display hardware can > >>>>>>> be shared between the encoder used for writeback and the physical > >>>>>>> display. > >>>>>>> > >>>>>>> In addition resources such as clocks and interrupts can > >>>>>>> also be shared between writeback and the real encoder. > >>>>>>> > >>>>>>> To accommodate such vendor drivers and hardware, allow > >>>>>>> real encoder to be passed for drm_writeback_connector. > >>>>>>> > >>>>>>> For existing clients, drm_writeback_connector_init() will use > >>>>>>> an internal_encoder under the hood and hence no changes will > >>>>>>> be needed. > >>>>>>> > >>>>>>> changes in v7: > >>>>>>> - move this change before the vc4 change in the series > >>>>>>> to minimize the changes to vendor drivers in drm core > >>>>>>> changes > >>>>>> > >>>>>> Why is this needed ? The drm_writeback_connector functions don't need > >>>>>> the drm_encoder after drm_writeback_connector_init() (or > >>>>>> drm_writeback_connector_init_with_encoder()) returns. > >>>>>> > >>>>> > >>>>> Sorry I didnt follow this comment. This change log is incorrect, so > >>>>> after changing the previous change in the series and modifying this, no > >>>>> further changes are needed to vc4, so I decided to drop the next change. > >>>>> So this change log is incorrect. I can remove this. > >>>>> > >>>>> Is that what you meant? > >>>> > >>>> So till the previous change, the only user of > >>>> drm_writeback_connector_init_with_encoder() was > >>>> drm_writeback_connector_init() which was still passing its own > >>>> internal_encoder. > >>>> > >>>> Only if the wb_connector->encoder is changed to a pointer, other vendor > >>>> drivers can pass their own encoder to > >>>> drm_writeback_connector_init_with_encoder(). > >>>> > >>>> Hence you are right that drm_writeback_connector functions do not need > >>>> drm_encoder after init() returns, but till this change is done, other > >>>> vendor drivers cannot directly call > >>>> drm_writeback_connector_init_with_encoder() because the encoder will not > >>>> be valid till then. > >>> > >>> Users of drm_writeback_connector_init_with_encoder() handle the encoder > >>> themselves, they can simply ignore drm_writeback_connector.encoder. The > >>> documentation of the encoder field needs to be updated though (I'd do so > >>> in the previous patch), to clearly mention that the field is valid only > >>> when using drm_writeback_connector_init(), not when calling > >>> drm_writeback_connector_init_with_encoder(). > >> > >> If we allow it to be unitialized, it might end with hard-to-trace > >> bugs, additional conditions, etc. > >> In my opnion we should: > >> - either make drm_writeback_connector.encoder a valid pointer > >> - or drop the field completely. > >> > >> And up to some point I'd vote for the second option. The code using > >> internal_encoder can continue using it directly. The code using > >> drm_writeback_connector_init_with_encoder() will manage encoder on > >> their own. We will loose a single entry point for wb's encoder, but do > >> we really need it? (Frankly speaking I didn't check.) > > > > As far as I understand, we went for the second option as Abhinav dropped > > this patch for the next version. > > I dropped the patch as there was no agreement yet and I didnt want to > block the series as its not really needed now but thats not option 2 > because wb_conn->encoder field remains there, just that its unused for > users using drm_writeback_connector_init_with_encoder(). > > I guess what Dmitry is suggesting is just drop that > wb_connector->encoder field completely. I don't think we can do that, as that field is used for the internal encoder :-) It could be renamed to internal_encoder if desired, but not dropped. I don't mind much either way, as long as we make it clear that drivers must never reference it directly. > >>>> Hope this clarifies it. > >>>> > >>>>>>> Signed-off-by: Abhinav Kumar > >>>>>>> Reviewed-by: Dmitry Baryshkov > >>>>>>> --- > >>>>>>> drivers/gpu/drm/drm_writeback.c | 18 ++++++++++++------ > >>>>>>> drivers/gpu/drm/vc4/vc4_txp.c | 4 ++-- > >>>>>>> include/drm/drm_writeback.h | 22 ++++++++++++++++++++-- > >>>>>>> 3 files changed, 34 insertions(+), 10 deletions(-) > >>>>>>> > >>>>>>> diff --git a/drivers/gpu/drm/drm_writeback.c > >>>>>>> b/drivers/gpu/drm/drm_writeback.c > >>>>>>> index 92658ad..0538674 100644 > >>>>>>> --- a/drivers/gpu/drm/drm_writeback.c > >>>>>>> +++ b/drivers/gpu/drm/drm_writeback.c > >>>>>>> @@ -180,21 +180,21 @@ int drm_writeback_connector_init(struct > >>>>>>> drm_device *dev, > >>>>>>> { > >>>>>>> int ret = 0; > >>>>>>> - drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs); > >>>>>>> + drm_encoder_helper_add(&wb_connector->internal_encoder, enc_helper_funcs); > >>>>>>> - wb_connector->encoder.possible_crtcs = possible_crtcs; > >>>>>>> + wb_connector->internal_encoder.possible_crtcs = possible_crtcs; > >>>>>>> - ret = drm_encoder_init(dev, &wb_connector->encoder, > >>>>>>> + ret = drm_encoder_init(dev, &wb_connector->internal_encoder, > >>>>>>> &drm_writeback_encoder_funcs, > >>>>>>> DRM_MODE_ENCODER_VIRTUAL, NULL); > >>>>>>> if (ret) > >>>>>>> return ret; > >>>>>>> - ret = drm_writeback_connector_init_with_encoder(dev, wb_connector, &wb_connector->encoder, > >>>>>>> - con_funcs, formats, n_formats); > >>>>>>> + ret = drm_writeback_connector_init_with_encoder(dev, wb_connector, > >>>>>>> + &wb_connector->internal_encoder, con_funcs, formats, n_formats); > >>>>>>> if (ret) > >>>>>>> - drm_encoder_cleanup(&wb_connector->encoder); > >>>>>>> + drm_encoder_cleanup(&wb_connector->internal_encoder); > >>>>>>> return ret; > >>>>>>> } > >>>>>>> @@ -239,6 +239,12 @@ int drm_writeback_connector_init_with_encoder(struct drm_device *dev, > >>>>>>> struct drm_mode_config *config = &dev->mode_config; > >>>>>>> int ret = create_writeback_properties(dev); > >>>>>>> + /* > >>>>>>> + * Assign the encoder passed to this API to the wb_connector's encoder. > >>>>>>> + * For drm_writeback_connector_init(), this shall be the internal_encoder > >>>>>>> + */ > >>>>>>> + wb_connector->encoder = enc; > >>>>>>> + > >>>>>>> if (ret != 0) > >>>>>>> return ret; > >>>>>>> diff --git a/drivers/gpu/drm/vc4/vc4_txp.c b/drivers/gpu/drm/vc4/vc4_txp.c > >>>>>>> index 3447eb6..7e063a9 100644 > >>>>>>> --- a/drivers/gpu/drm/vc4/vc4_txp.c > >>>>>>> +++ b/drivers/gpu/drm/vc4/vc4_txp.c > >>>>>>> @@ -159,7 +159,7 @@ struct vc4_txp { > >>>>>>> static inline struct vc4_txp *encoder_to_vc4_txp(struct drm_encoder *encoder) > >>>>>>> { > >>>>>>> - return container_of(encoder, struct vc4_txp, connector.encoder); > >>>>>>> + return container_of(encoder, struct vc4_txp, connector.internal_encoder); > >>>>>>> } > >>>>>>> static inline struct vc4_txp *connector_to_vc4_txp(struct drm_connector *conn) > >>>>>>> @@ -507,7 +507,7 @@ static int vc4_txp_bind(struct device *dev, struct device *master, void *data) > >>>>>>> if (ret) > >>>>>>> return ret; > >>>>>>> - encoder = &txp->connector.encoder; > >>>>>>> + encoder = txp->connector.encoder; > >>>>>>> encoder->possible_crtcs = drm_crtc_mask(crtc); > >>>>>>> ret = devm_request_irq(dev, irq, vc4_txp_interrupt, 0, > >>>>>>> diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h > >>>>>>> index bb306fa..3fbae9d 100644 > >>>>>>> --- a/include/drm/drm_writeback.h > >>>>>>> +++ b/include/drm/drm_writeback.h > >>>>>>> @@ -25,13 +25,31 @@ struct drm_writeback_connector { > >>>>>>> struct drm_connector base; > >>>>>>> /** > >>>>>>> - * @encoder: Internal encoder used by the connector to fulfill > >>>>>>> + * @encoder: handle to drm_encoder used by the connector to fulfill > >>>>>>> * the DRM framework requirements. The users of the > >>>>>>> * @drm_writeback_connector control the behaviour of the @encoder > >>>>>>> * by passing the @enc_funcs parameter to drm_writeback_connector_init() > >>>>>>> * function. > >>>>>>> + * > >>>>>>> + * For some vendor drivers, the hardware resources are shared between > >>>>>>> + * writeback encoder and rest of the display pipeline. > >>>>>>> + * To accommodate such cases, encoder is a handle to the real encoder > >>>>>>> + * hardware. > >>>>>>> + * > >>>>>>> + * For current existing writeback users, this shall continue to be the > >>>>>>> + * embedded encoder for the writeback connector. > >>>>>>> + */ > >>>>>>> + struct drm_encoder *encoder; > >>>>>>> + > >>>>>>> + /** > >>>>>>> + * @internal_encoder: internal encoder used by writeback when > >>>>>>> + * drm_writeback_connector_init() is used. > >>>>>>> + * @encoder will be assigned to this for those cases > >>>>>>> + * > >>>>>>> + * This will be unused when drm_writeback_connector_init_with_encoder() > >>>>>>> + * is used. > >>>>>>> */ > >>>>>>> - struct drm_encoder encoder; > >>>>>>> + struct drm_encoder internal_encoder; > >>>>>>> /** > >>>>>>> * @pixel_formats_blob_ptr: -- Regards, Laurent Pinchart