From: Neil Armstrong <neil.armstrong@linaro.org>
To: Douglas Anderson <dianders@chromium.org>,
dri-devel@lists.freedesktop.org
Cc: Linus Walleij <linus.walleij@linaro.org>,
lvzhaoxiong@huaqin.corp-partner.google.com,
Jani Nikula <jani.nikula@linux.intel.com>,
Hsin-Yi Wang <hsinyi@google.com>,
Javier Martinez Canillas <javierm@redhat.com>,
Joel Selvaraj <jo@jsfamily.in>,
Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
Cong Yang <yangcong5@huaqin.corp-partner.google.com>,
Sam Ravnborg <sam@ravnborg.org>, Daniel Vetter <daniel@ffwll.ch>,
David Airlie <airlied@gmail.com>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 4/8] drm/mipi-dsi: Introduce mipi_dsi_*_write_seq_multi()
Date: Mon, 29 Apr 2024 11:38:01 +0200 [thread overview]
Message-ID: <2af446d3-7834-4a6b-897b-b14c6bccff65@linaro.org> (raw)
In-Reply-To: <20240426165839.v2.4.Ie94246c30fe95101e0e26dd5f96e976dbeb8f242@changeid>
Hello Mister Anderson,
On 27/04/2024 01:58, Douglas Anderson wrote:
> The current mipi_dsi_*_write_seq() macros are non-intutitive because
> they contain a hidden "return" statement that will return out of the
> _caller_ of the macro. Let's mark them as deprecated and instead
> introduce some new macros that are more intuitive.
>
> These new macros are less optimal when an error occurs but should
> behave more optimally when there is no error. Specifically these new
> macros cause smaller code to get generated and the code size savings
> (less to fetch from RAM, less cache space used, less RAM used) are
> important. Since the error case isn't something we need to optimize
> for and these new macros are easier to understand and more flexible,
> they should be used.
>
> After converting to use these new functions, one example shows some
> nice savings while also being easier to understand.
>
> $ scripts/bloat-o-meter \
> ...after/panel-novatek-nt36672e.ko \
> ...ctx/panel-novatek-nt36672e.ko
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-988 (-988)
> Function old new delta
> nt36672e_1080x2408_60hz_init 6236 5248 -988
> Total: Before=10651, After=9663, chg -9.28%
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
> Right now this patch introduces two new functions in
> drm_mipi_dsi.c. Alternatively we could have changed the prototype of
> the "chatty" functions and made the deprecated macros adapt to the new
> prototype. While this sounds nice, it bloated callers of the
> deprecated functioin a bit because it caused the compiler to emit less
> optimal code. It doesn't seem terrible to add two more functions, so I
> went that way.
>
> Changes in v2:
> - New
>
> drivers/gpu/drm/drm_mipi_dsi.c | 56 +++++++++++++++++++++++++++++++++
> include/drm/drm_mipi_dsi.h | 57 ++++++++++++++++++++++++++++++++++
> 2 files changed, 113 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> index 1e062eda3b88..b7c75a4396e6 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -792,6 +792,34 @@ int mipi_dsi_generic_write_chatty(struct mipi_dsi_device *dsi,
> }
> EXPORT_SYMBOL(mipi_dsi_generic_write_chatty);
>
<snip>
> };
>
> +/**
> + * struct mipi_dsi_multi_context - Context to call multiple MIPI DSI funcs in a row
> + * @dsi: Pointer to the MIPI DSI device
> + * @accum_err: Storage for the accumulated error over the multiple calls. Init
> + * to 0. If a function encounters an error then the error code will be
> + * stored here. If you call a function and this points to a non-zero
> + * value then the function will be a noop. This allows calling a function
> + * many times in a row and just checking the error at the end to see if
> + * any of them failed.
> + */
> +
> +struct mipi_dsi_multi_context {
> + struct mipi_dsi_device *dsi;
> + int accum_err;
> +};
I like the design, but having a context struct seems over-engineered while we could pass
a single int over without encapsulating it with mipi_dsi_multi_context.
void mipi_dsi_dcs_write_buffer_multi(struct mipi_dsi_multi_context *ctx,
const void *data, size_t len);
vs
void mipi_dsi_dcs_write_buffer_multi(struct mipi_dsi_device *dsi, int *accum_err,
const void *data, size_t len);
is the same, and it avoids having to declare a mipi_dsi_multi_context and set ctx->dsi,
and I'll find it much easier to migrate, just add a &ret and make sure ret is initialized to 0.
<snip>
next prev parent reply other threads:[~2024-04-29 9:38 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 23:58 [PATCH v2 0/8] drm/mipi-dsi: Reduce bloat and add funcs for cleaner init seqs Douglas Anderson
2024-04-26 23:58 ` [PATCH v2 1/8] drm/mipi-dsi: Fix theoretical int overflow in mipi_dsi_dcs_write_seq() Douglas Anderson
2024-04-27 1:44 ` Dmitry Baryshkov
2024-04-27 6:22 ` Sam Ravnborg
2024-04-29 21:42 ` Doug Anderson
2024-04-26 23:58 ` [PATCH v2 2/8] drm/mipi-dsi: Fix theoretical int overflow in mipi_dsi_generic_write_seq() Douglas Anderson
2024-04-26 23:58 ` [PATCH v2 3/8] drm/mipi-dsi: Reduce driver bloat of mipi_dsi_*_write_seq() Douglas Anderson
2024-04-27 2:05 ` Dmitry Baryshkov
2024-04-26 23:58 ` [PATCH v2 4/8] drm/mipi-dsi: Introduce mipi_dsi_*_write_seq_multi() Douglas Anderson
2024-04-27 6:32 ` Sam Ravnborg
2024-04-29 14:13 ` Doug Anderson
2024-04-29 9:38 ` Neil Armstrong [this message]
2024-04-29 14:26 ` Doug Anderson
2024-04-29 15:39 ` Jani Nikula
2024-05-01 15:49 ` Doug Anderson
2024-05-01 15:57 ` Dmitry Baryshkov
2024-05-06 6:21 ` Linus Walleij
2024-04-26 23:58 ` [PATCH v2 5/8] drm/mipi-dsi: mipi_dsi_*_write functions don't need to ratelimit prints Douglas Anderson
2024-04-26 23:58 ` [PATCH v2 6/8] drm/panel: novatek-nt36672e: Switch to mipi_dsi_dcs_write_seq_multi() Douglas Anderson
2024-04-26 23:58 ` [PATCH v2 7/8] drm/panel: boe-tv101wum-nl6: Don't use a table for initting commands Douglas Anderson
2024-04-26 23:58 ` [PATCH v2 8/8] drm/panel: boe-tv101wum-nl6: Convert hex to lowercase Douglas Anderson
2024-04-27 8:48 ` Dmitry Baryshkov
2024-04-29 9:20 ` [PATCH v2 0/8] drm/mipi-dsi: Reduce bloat and add funcs for cleaner init seqs Jani Nikula
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