Commit 3b724909 authored by Douglas Anderson's avatar Douglas Anderson Committed by Neil Armstrong
Browse files

drm/mipi-dsi: Reduce driver bloat of mipi_dsi_*_write_seq() 



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: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: default avatarNeil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarDouglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20240514102056.v5.4.Id15fae80582bc74a0d4f1338987fa375738f45b9@changeid


Signed-off-by: default avatarNeil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240514102056.v5.4.Id15fae80582bc74a0d4f1338987fa375738f45b9@changeid
parent 7d3f6aca

drivers/gpu/drm/drm_mipi_dsi.c

+56 −0
Original line number Diff line number Diff line
@@ -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()

 * 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()

 * 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

include/drm/drm_mipi_dsi.h

+26 −21
Original line number Diff line number Diff line
@@ -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,
@@ -311,23 +315,28 @@ 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); \

		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
@@ -335,14 +344,10 @@ int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi, 
#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);                                  \

		int ret;                                                       \

		ret = mipi_dsi_dcs_write_buffer_chatty(dsi, d, ARRAY_SIZE(d)); \

		if (ret < 0)                                                   \

			return ret;                                            \

		}                                                           \

	} while (0)



/**