drm/i915/gmbus: use generic poll_timeout*() instead of wait_for*()

Prefer generic poll helpers over i915 custom helpers.

The "two tier" wait_for_us() + wait_for() combination appeared without
much explanation in commit 4e6c2d58ba86 ("drm/i915: Take forcewake once
for the entire GMBUS transaction"). Try to mimic roughly the same with
the generic helpers.

wait_for_us() with 10 us or shorter timeouts ends up in
_wait_for_atomic(). Thus use poll_timeout_us_atomic() for the first try,
with the same 2 us timeout and no sleep.

For the fallback, the functional change is losing the exponentially
growing sleep of wait_for(), which used to be 10, 20, 40, ..., 640, and
1280 us. Use an arbitrary constant 500 us sleep instead. The timeout
remains at 50 ms.

Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://lore.kernel.org/r/564b397352c53a1116519fb2d53050c0426bc0dc.1756383233.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_gmbus.c b/drivers/gpu/drm/i915/display/intel_gmbus.c
index 063335053d13487a9f7004615f76cac6c0434e6b..358210adb8f847cfd8f3082ae0617e02f3c7225e 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_gmbus.c
+++ b/drivers/gpu/drm/i915/display/intel_gmbus.c
@@ -30,13 +30,13 @@
 #include <linux/export.h>
 #include <linux/i2c-algo-bit.h>
 #include <linux/i2c.h>
+#include <linux/iopoll.h>
 
 #include <drm/display/drm_hdcp_helper.h>
 
 #include "i915_drv.h"
 #include "i915_irq.h"
 #include "i915_reg.h"
-#include "i915_utils.h"
 #include "intel_de.h"
 #include "intel_display_regs.h"
 #include "intel_display_types.h"
@@ -415,11 +415,14 @@ static int gmbus_wait(struct intel_display *display, u32 status, u32 irq_en)
        intel_de_write_fw(display, GMBUS4(display), irq_en);
 
        status |= GMBUS_SATOER;
-       ret = wait_for_us((gmbus2 = intel_de_read_fw(display, GMBUS2(display))) & status,
-                         2);
+
+       ret = poll_timeout_us_atomic(gmbus2 = intel_de_read_fw(display, GMBUS2(display)),
+                                    gmbus2 & status,
+                                    0, 2, false);
        if (ret)
-               ret = wait_for((gmbus2 = intel_de_read_fw(display, GMBUS2(display))) & status,
-                              50);
+               ret = poll_timeout_us(gmbus2 = intel_de_read_fw(display, GMBUS2(display)),
+                                     gmbus2 & status,
+                                     500, 50 * 1000, false);
 
        intel_de_write_fw(display, GMBUS4(display), 0);
        remove_wait_queue(&display->gmbus.wait_queue, &wait);