Re: [PATCH 2/2] drm/i915/gmbus: Add Wa_16025573575 for PTL for bit-bashing

[Nautiyal, Ankit K]

On 7/2/2025 6:41 PM, Gustavo Sousa wrote:
Quoting Ankit Nautiyal (2025-07-02 05:46:19-03:00)
As per Wa_16025573575 for PTL, set the GPIO masks bit before starting
bit-bashing and maintain value through the bit-bashing sequence.
After bit-bashing sequence is done, clear the GPIO masks bits.

v2:
-Use new helper for display workarounds. (Jani)
-Use a separate if-block for the workaround. (Gustavo)

Signed-off-by: Ankit Nautiyal <ankit.k.nauti...@intel.com>
---
.../gpu/drm/i915/display/intel_display_wa.c   |  7 ++++
.../gpu/drm/i915/display/intel_display_wa.h   |  1 +
drivers/gpu/drm/i915/display/intel_gmbus.c    | 34 +++++++++++++++++--
3 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_wa.c 
b/drivers/gpu/drm/i915/display/intel_display_wa.c
index f5e8d58d9a68..12d1df5981f7 100644
--- a/drivers/gpu/drm/i915/display/intel_display_wa.c
+++ b/drivers/gpu/drm/i915/display/intel_display_wa.c
@@ -42,11 +42,18 @@ void intel_display_wa_apply(struct intel_display *display)
                 gen11_display_wa_apply(display);
}

+static bool intel_display_needs_wa_16025573575(struct intel_display *display)
+{
+        return DISPLAY_VER(display) == 30;
We should also check for 30.02.

I was thinking to add a separate patch for this, but yeah can include in 
this patch as well.



+}
+
bool __intel_display_wa(struct intel_display *display, enum intel_display_wa wa)
{
         switch (wa) {
         case INTEL_DISPLAY_WA_16023588340:
                 return intel_display_needs_wa_16023588340(display);
+        case INTEL_DISPLAY_WA_16025573575:
+                return intel_display_needs_wa_16025573575(display);
While it makes sense to have function
intel_display_needs_wa_16023588340() (at least for now), I wonder if the
same could be said about intel_display_needs_wa_16025573575()...

Maybe it would be simpler to just inline the conditions with a single
line here instead of adding 5 extra lines to the file.


IMHO, it's better to keep __intel_display_wa() simple and uniform. In 
the future,

some workarounds might involve complex conditions (such as checks for 
steppings,
applicability to multiple platforms or variants)
which could make the switch-case harder to read if inlined.

Having dedicated functions like intel_display_needs_wa_xxxx() helps 
encapsulate that logic cleanly.

Mixing inlined conditions with function calls would reduce consistency 
and readability.


Thanks & Regards,

Ankit



--
Gustavo Sousa

         default:
                 drm_WARN(display->drm, 1, "Missing Wa number: %d\n", wa);
                 break;
diff --git a/drivers/gpu/drm/i915/display/intel_display_wa.h 
b/drivers/gpu/drm/i915/display/intel_display_wa.h
index 146ee70d66f7..d3d241992e55 100644
--- a/drivers/gpu/drm/i915/display/intel_display_wa.h
+++ b/drivers/gpu/drm/i915/display/intel_display_wa.h
@@ -23,6 +23,7 @@ bool intel_display_needs_wa_16023588340(struct intel_display 
*display);

enum intel_display_wa {
         INTEL_DISPLAY_WA_16023588340,
+        INTEL_DISPLAY_WA_16025573575,
};

bool __intel_display_wa(struct intel_display *display, enum intel_display_wa 
wa);
diff --git a/drivers/gpu/drm/i915/display/intel_gmbus.c 
b/drivers/gpu/drm/i915/display/intel_gmbus.c
index 0d73f32fe7f1..95cab11c9cde 100644
--- a/drivers/gpu/drm/i915/display/intel_gmbus.c
+++ b/drivers/gpu/drm/i915/display/intel_gmbus.c
@@ -39,6 +39,7 @@
#include "intel_de.h"
#include "intel_display_regs.h"
#include "intel_display_types.h"
+#include "intel_display_wa.h"
#include "intel_gmbus.h"
#include "intel_gmbus_regs.h"

@@ -241,11 +242,18 @@ static u32 get_reserved(struct intel_gmbus *bus)
{
         struct intel_display *display = bus->display;
         u32 reserved = 0;
+        u32 preserve_bits = 0;

         /* On most chips, these bits must be preserved in software. */
         if (!display->platform.i830 && !display->platform.i845g)
-                reserved = intel_de_read_notrace(display, bus->gpio_reg) &
-                        (GPIO_DATA_PULLUP_DISABLE | GPIO_CLOCK_PULLUP_DISABLE);
+                preserve_bits |= GPIO_DATA_PULLUP_DISABLE | 
GPIO_CLOCK_PULLUP_DISABLE;
+
+        /* PTL: Wa_16025573575: the masks bits need to be preserved through 
out */
+        if (intel_display_wa(display, 16025573575))
+                preserve_bits |= GPIO_CLOCK_DIR_MASK | GPIO_CLOCK_VAL_MASK |
+                                 GPIO_DATA_DIR_MASK | GPIO_DATA_VAL_MASK;
+
+        reserved = intel_de_read_notrace(display, bus->gpio_reg) & 
preserve_bits;

         return reserved;
}
@@ -308,6 +316,22 @@ static void set_data(void *data, int state_high)
         intel_de_posting_read(display, bus->gpio_reg);
}

+static void
+ptl_handle_mask_bits(struct intel_gmbus *bus, bool set)
+{
+        struct intel_display *display = bus->display;
+        u32 reg_val = intel_de_read_notrace(display, bus->gpio_reg);
+        u32 mask_bits = GPIO_CLOCK_DIR_MASK | GPIO_CLOCK_VAL_MASK |
+                        GPIO_DATA_DIR_MASK | GPIO_DATA_VAL_MASK;
+        if (set)
+                reg_val |= mask_bits;
+        else
+                reg_val &= ~mask_bits;
+
+        intel_de_write_notrace(display, bus->gpio_reg, reg_val);
+        intel_de_posting_read(display, bus->gpio_reg);
+}
+
static int
intel_gpio_pre_xfer(struct i2c_adapter *adapter)
{
@@ -319,6 +343,9 @@ intel_gpio_pre_xfer(struct i2c_adapter *adapter)
         if (display->platform.pineview)
                 pnv_gmbus_clock_gating(display, false);

+        if (intel_display_wa(display, 16025573575))
+                ptl_handle_mask_bits(bus, true);
+
         set_data(bus, 1);
         set_clock(bus, 1);
         udelay(I2C_RISEFALL_TIME);
@@ -336,6 +363,9 @@ intel_gpio_post_xfer(struct i2c_adapter *adapter)

         if (display->platform.pineview)
                 pnv_gmbus_clock_gating(display, true);
+
+        if (intel_display_wa(display, 16025573575))
+                ptl_handle_mask_bits(bus, false);
}

static void
--
2.45.2