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Date: Thu, 2 May 2024 09:27:46 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Douglas Anderson <dianders@...omium.org>, dri-devel@...ts.freedesktop.org
Cc: Linus Walleij <linus.walleij@...aro.org>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
Cong Yang <yangcong5@...qin.corp-partner.google.com>,
Hsin-Yi Wang <hsinyi@...gle.com>, Brian Norris <briannorris@...omium.org>,
Sam Ravnborg <sam@...nborg.org>,
Javier Martinez Canillas <javierm@...hat.com>, Joel Selvaraj
<jo@...amily.in>, lvzhaoxiong@...qin.corp-partner.google.com,
Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...il.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/9] drm/mipi-dsi: Reduce driver bloat of
mipi_dsi_*_write_seq()
On 01/05/2024 17:41, Douglas Anderson wrote:
> Through a cooperative effort between Hsin-Yi Wang and Dmitry
> Baryshkov, we have realized the dev_err() in the
> mipi_dsi_*_write_seq() macros was causing quite a bit of bloat to the
> kernel. Let's hoist this call into drm_mipi_dsi.c by adding a "chatty"
> version of the functions that includes the print. While doing this,
> add a bit more comments to these macros making it clear that they
> print errors and also that they return out of _the caller's_ function.
>
> Without any changes to clients this gives a nice savings. Building
> with my build system shows one example:
>
> $ scripts/bloat-o-meter \
> .../before/panel-novatek-nt36672e.ko \
> .../after/panel-novatek-nt36672e.ko
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-4404 (-4404)
> Function old new delta
> nt36672e_1080x2408_60hz_init 10640 6236 -4404
> Total: Before=15055, After=10651, chg -29.25%
>
> Note that given the change in location of the print it's harder to
> include the "cmd" in the printout for mipi_dsi_dcs_write_seq() since,
> theoretically, someone could call the new chatty function with a
> zero-size array and it would be illegal to dereference data[0].
> There's a printk format to print the whole buffer and this is probably
> more useful for debugging anyway. Given that we're doing this for
> mipi_dsi_dcs_write_seq(), let's also print the buffer for
> mipi_dsi_generic_write_seq() in the error case.
>
> It should be noted that the current consensus of DRM folks is that the
> mipi_dsi_*_write_seq() should be deprecated due to the non-intuitive
> return behavior. A future patch will formally mark them as deprecated
> and provide an alternative.
>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>
> Changes in v3:
> - Rebased upon patch to remove ratelimit of prints.
>
> Changes in v2:
> - Add some comments to the macros about printing and returning.
> - Change the way err value is handled in prep for next patch.
> - Modify commit message now that this is part of a series.
> - Rebased upon patches to avoid theoretical int overflow.
>
> drivers/gpu/drm/drm_mipi_dsi.c | 56 ++++++++++++++++++++++++++++++++++
> include/drm/drm_mipi_dsi.h | 47 +++++++++++++++-------------
> 2 files changed, 82 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> index 795001bb7ff1..8593d9ed5891 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -764,6 +764,34 @@ ssize_t mipi_dsi_generic_write(struct mipi_dsi_device *dsi, const void *payload,
> }
> EXPORT_SYMBOL(mipi_dsi_generic_write);
>
> +/**
> + * mipi_dsi_generic_write_chatty() - mipi_dsi_generic_write() w/ an error log
> + * @dsi: DSI peripheral device
> + * @payload: buffer containing the payload
> + * @size: size of payload buffer
> + *
> + * Like mipi_dsi_generic_write() but includes a dev_err_ratelimited()
> + * call for you and returns 0 upon success, not the number of bytes sent.
> + *
> + * Return: 0 on success or a negative error code on failure.
> + */
> +int mipi_dsi_generic_write_chatty(struct mipi_dsi_device *dsi,
> + const void *payload, size_t size)
> +{
> + struct device *dev = &dsi->dev;
> + ssize_t ret;
> +
> + ret = mipi_dsi_generic_write(dsi, payload, size);
> + if (ret < 0) {
> + dev_err(dev, "sending generic data %*ph failed: %zd\n",
> + (int)size, payload, ret);
> + return ret;
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(mipi_dsi_generic_write_chatty);
> +
> /**
> * mipi_dsi_generic_read() - receive data using a generic read packet
> * @dsi: DSI peripheral device
> @@ -852,6 +880,34 @@ ssize_t mipi_dsi_dcs_write_buffer(struct mipi_dsi_device *dsi,
> }
> EXPORT_SYMBOL(mipi_dsi_dcs_write_buffer);
>
> +/**
> + * mipi_dsi_dcs_write_buffer_chatty - mipi_dsi_dcs_write_buffer() w/ an error log
> + * @dsi: DSI peripheral device
> + * @data: buffer containing data to be transmitted
> + * @len: size of transmission buffer
> + *
> + * Like mipi_dsi_dcs_write_buffer() but includes a dev_err_ratelimited()
> + * call for you and returns 0 upon success, not the number of bytes sent.
> + *
> + * Return: 0 on success or a negative error code on failure.
> + */
> +int mipi_dsi_dcs_write_buffer_chatty(struct mipi_dsi_device *dsi,
> + const void *data, size_t len)
> +{
> + struct device *dev = &dsi->dev;
> + ssize_t ret;
> +
> + ret = mipi_dsi_dcs_write_buffer(dsi, data, len);
> + if (ret < 0) {
> + dev_err(dev, "sending dcs data %*ph failed: %zd\n",
> + (int)len, data, ret);
> + return ret;
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(mipi_dsi_dcs_write_buffer_chatty);
> +
> /**
> * mipi_dsi_dcs_write() - send DCS write command
> * @dsi: DSI peripheral device
> diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
> index 67967be48dbd..6d68d9927f46 100644
> --- a/include/drm/drm_mipi_dsi.h
> +++ b/include/drm/drm_mipi_dsi.h
> @@ -256,6 +256,8 @@ int mipi_dsi_picture_parameter_set(struct mipi_dsi_device *dsi,
>
> ssize_t mipi_dsi_generic_write(struct mipi_dsi_device *dsi, const void *payload,
> size_t size);
> +int mipi_dsi_generic_write_chatty(struct mipi_dsi_device *dsi,
> + const void *payload, size_t size);
> ssize_t mipi_dsi_generic_read(struct mipi_dsi_device *dsi, const void *params,
> size_t num_params, void *data, size_t size);
>
> @@ -279,6 +281,8 @@ enum mipi_dsi_dcs_tear_mode {
>
> ssize_t mipi_dsi_dcs_write_buffer(struct mipi_dsi_device *dsi,
> const void *data, size_t len);
> +int mipi_dsi_dcs_write_buffer_chatty(struct mipi_dsi_device *dsi,
> + const void *data, size_t len);
> ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, u8 cmd,
> const void *data, size_t len);
> ssize_t mipi_dsi_dcs_read(struct mipi_dsi_device *dsi, u8 cmd, void *data,
> @@ -311,38 +315,39 @@ int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
>
> /**
> * mipi_dsi_generic_write_seq - transmit data using a generic write packet
> + *
> + * This macro will print errors for you and will RETURN FROM THE CALLING
> + * FUNCTION (yes this is non-intuitive) upon error.
> + *
> * @dsi: DSI peripheral device
> * @seq: buffer containing the payload
> */
> -#define mipi_dsi_generic_write_seq(dsi, seq...) \
> - do { \
> - static const u8 d[] = { seq }; \
> - struct device *dev = &dsi->dev; \
> - ssize_t ret; \
> - ret = mipi_dsi_generic_write(dsi, d, ARRAY_SIZE(d)); \
> - if (ret < 0) { \
> - dev_err(dev, "transmit data failed: %zd\n", ret); \
> - return ret; \
> - } \
> +#define mipi_dsi_generic_write_seq(dsi, seq...) \
> + do { \
> + static const u8 d[] = { seq }; \
> + int ret; \
> + ret = mipi_dsi_generic_write_chatty(dsi, d, ARRAY_SIZE(d)); \
> + if (ret < 0) \
> + return ret; \
> } while (0)
>
> /**
> * mipi_dsi_dcs_write_seq - transmit a DCS command with payload
> + *
> + * This macro will print errors for you and will RETURN FROM THE CALLING
> + * FUNCTION (yes this is non-intuitive) upon error.
> + *
> * @dsi: DSI peripheral device
> * @cmd: Command
> * @seq: buffer containing data to be transmitted
> */
> -#define mipi_dsi_dcs_write_seq(dsi, cmd, seq...) \
> - do { \
> - static const u8 d[] = { cmd, seq }; \
> - struct device *dev = &dsi->dev; \
> - ssize_t ret; \
> - ret = mipi_dsi_dcs_write_buffer(dsi, d, ARRAY_SIZE(d)); \
> - if (ret < 0) { \
> - dev_err(dev, "sending command %#02x failed: %zd\n", \
> - cmd, ret); \
> - return ret; \
> - } \
> +#define mipi_dsi_dcs_write_seq(dsi, cmd, seq...) \
> + do { \
> + static const u8 d[] = { cmd, seq }; \
> + int ret; \
> + ret = mipi_dsi_dcs_write_buffer_chatty(dsi, d, ARRAY_SIZE(d)); \
> + if (ret < 0) \
> + return ret; \
> } while (0)
>
> /**
Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>
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