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. Specifically
the macro was inlined and thus the error report call was inlined into
every call to mipi_dsi_dcs_write_seq() and
mipi_dsi_generic_write_seq(). By using a call to a "chatty" function,
the usage is reduced to one call in the chatty function and a function
call at the invoking site.
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@linaro.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
Changes in v4:
- Update wording as per Linus W.
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)
/**
--
2.45.0.rc1.225.g2a3ae87e7f-googHi,
On Wed, May 08, 2024 at 01:51:46PM -0700, 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. Specifically
> the macro was inlined and thus the error report call was inlined into
> every call to mipi_dsi_dcs_write_seq() and
> mipi_dsi_generic_write_seq(). By using a call to a "chatty" function,
> the usage is reduced to one call in the chatty function and a function
> call at the invoking site.
>
> 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@linaro.org>
> Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
> Changes in v4:
> - Update wording as per Linus W.
>
> 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()
You mention in both functions that it's calling 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);
... but it doesn't.
Maxime
Hi,
On Mon, May 13, 2024 at 2:30 AM Maxime Ripard <mripard@kernel.org> wrote:
>
> Hi,
>
> On Wed, May 08, 2024 at 01:51:46PM -0700, 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. Specifically
> > the macro was inlined and thus the error report call was inlined into
> > every call to mipi_dsi_dcs_write_seq() and
> > mipi_dsi_generic_write_seq(). By using a call to a "chatty" function,
> > the usage is reduced to one call in the chatty function and a function
> > call at the invoking site.
> >
> > 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@linaro.org>
> > Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
> > Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> > Signed-off-by: Douglas Anderson <dianders@chromium.org>
> > ---
> >
> > Changes in v4:
> > - Update wording as per Linus W.
> >
> > 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()
>
> You mention in both functions that it's calling 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);
>
> ... but it doesn't.
Whoops, thanks for catching this! I'll plan to send a v5 tomorrow to
fix this and then I'll still plan to land the series on Thursday
unless anything major comes up.
-Doug
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