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@xxxxxxxxxxxx>
---
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>
