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Mon, 14 Sep 2026 17:42:53 +0000 (UTC) From: David Heidelberg via B4 Relay Date: Mon, 14 Sep 2026 19:42:47 +0200 Subject: [PATCH v2 1/3] backlight: qcom-wled: Fix WLED3 brightness register stride Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260914-qcom-wled-backlight-v2-1-a908d9233e93@ixit.cz> References: <20260914-qcom-wled-backlight-v2-0-a908d9233e93@ixit.cz> In-Reply-To: <20260914-qcom-wled-backlight-v2-0-a908d9233e93@ixit.cz> To: Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller , Kiran Gunda , Marco Mattiolo , =?utf-8?q?Barnab=C3=A1s_Cz=C3=A9m=C3=A1n?= Cc: linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, phone-devel@vger.kernel.org, Konrad Dybcio , Joel Selvaraj , David Heidelberg , stable@vger.kernel.org X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; 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a=openpgp; fpr=D77A09CFEEDC2BBD53A7047460023FC4D3492072 X-Endpoint-Received: by B4 Relay for david@ixit.cz/default with auth_id=355 X-Original-From: David Heidelberg Reply-To: david@ixit.cz From: David Heidelberg WLED3 has a 16-bit brightness register pair per string, at 0x40 + 2*n, which is what the pm8941-wled driver wrote to: rc =3D regmap_bulk_write(wled->regmap, wled->addr + WLED3_CTRL_REG_VAL_BASE + 2 * i, v, 2); The restructuring for WLED3 turned that into WLED3_SINK_REG_BRIGHT(n), defined as 0x40 + n, so the two byte writes for consecutive strings overlap: string 1 overwrites the MSB of string 0 with its own LSB, and with the default three strings only string 1 ends up with the requested value. Use the 2 byte stride. Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED= 3") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: David Heidelberg --- drivers/video/backlight/qcom-wled.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/= qcom-wled.c index 650dd95f06ef5..22c35da72dce3 100644 --- a/drivers/video/backlight/qcom-wled.c +++ b/drivers/video/backlight/qcom-wled.c @@ -54,17 +54,17 @@ #define WLED3_SINK_REG_SYNC 0x47 #define WLED3_SINK_REG_SYNC_CLEAR 0x00 =20 #define WLED3_SINK_REG_CURR_SINK 0x4f #define WLED3_SINK_REG_CURR_SINK_MASK GENMASK(7, 5) #define WLED3_SINK_REG_CURR_SINK_SHFT 5 =20 /* WLED3 specific per-'string' registers below */ -#define WLED3_SINK_REG_BRIGHT(n) (0x40 + n) +#define WLED3_SINK_REG_BRIGHT(n) (0x40 + (n * 0x10)) =20 #define WLED3_SINK_REG_STR_MOD_EN(n) (0x60 + (n * 0x10)) #define WLED3_SINK_REG_STR_MOD_MASK BIT(7) =20 #define WLED3_SINK_REG_STR_FULL_SCALE_CURR(n) (0x62 + (n * 0x10)) #define WLED3_SINK_REG_STR_FULL_SCALE_CURR_MASK GENMASK(4, 0) =20 #define WLED3_SINK_REG_STR_MOD_SRC(n) (0x63 + (n * 0x10)) --=20 2.55.0 From nobody Fri Sep 25 09:22:26 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6BDEB49B1E0; 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charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260914-qcom-wled-backlight-v2-2-a908d9233e93@ixit.cz> References: <20260914-qcom-wled-backlight-v2-0-a908d9233e93@ixit.cz> In-Reply-To: <20260914-qcom-wled-backlight-v2-0-a908d9233e93@ixit.cz> To: Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller , Kiran Gunda , Marco Mattiolo , =?utf-8?q?Barnab=C3=A1s_Cz=C3=A9m=C3=A1n?= Cc: linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, phone-devel@vger.kernel.org, Konrad Dybcio , Joel Selvaraj , David Heidelberg , stable@vger.kernel.org X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=6057; i=david@ixit.cz; h=from:subject:message-id; bh=Vqrnik48gtJA54Q6xt1CXnDnTO5laYfiKv3N097zbZ8=; b=owEBbQKS/ZANAwAIAWACP8TTSSByAcsmYgBqqDIcuHb4gRqOsnQFZt+W7MWg/FqVvU5X1hw79 BUBt2/0t66JAjMEAAEIAB0WIQTXegnP7twrvVOnBHRgAj/E00kgcgUCaqgyHAAKCRBgAj/E00kg cpsdD/9tuwjChsSit3ed4inDEzY/yslaV+l/fbUe6Ra0gSEyatJBDtMHDlm8Sw2X/SbmJmYJjS3 RXxfrqq0ZGZRlNLsVShvJlADJqth7IJUyxttoMv5HWeC3I2Qyy2lfn0LDY3JgDsP/+W09J/lZWD uqtalvvR+rmv1AX6aDppjScl+J5ebb3c24jTlyMCjcQ2ypyWKgts2K0R6M5cgiTAQ36/vDOrg3h c/1rWfua9/iXVI1qNVY2/6Oyb5qtODEy0DaORNf0BX0NzvbZCoQbzlUZLFFIqNBOVc6P4NXkRbl SY5/97F6apcfqM2HpO9RjEX0s+IS6C+J6g/NwD1KiWdKa2Rwg+9+TKkxtyVdNPMkWh7lWu1kGOC gV00WnM5sa5T2GTVc2wIFpYzXfXOMV06s4yn0nSl7ZmeUA5OW06Jx6SaBVr6SeJLsSugPEAYsDB 9UoNx0UiLnUY/EhcehydIW7k6pa7luaQaqW8ozWtjmppbT/llVv6tCEpfWIPI+xiWz6/m7Yf2bY D4+Ma1g2dD1A3ZuXGkxttakpsxX7LQ8Bpatk3MwhpdK3bF777vndHRvjMLUsKVWrNTbPhM9MimI 3LHiN3+wAjfdBNoIzB86MPIerSmJ3kPnQRYn0uioYUYiEPlppJhSgcTVDlZLgV9jUAuy423NYiy dbVapvSeBK5o3pA== X-Developer-Key: i=david@ixit.cz; a=openpgp; fpr=D77A09CFEEDC2BBD53A7047460023FC4D3492072 X-Endpoint-Received: by B4 Relay for david@ixit.cz/default with auth_id=355 X-Original-From: David Heidelberg Reply-To: david@ixit.cz From: David Heidelberg wled_configure_ovp_irq() derives the initial state of the OVP interrupt from the hardware: /* Keep OVP irq disabled until module is enabled */ if (!(val & WLED3_CTRL_REG_MOD_EN_MASK)) disable_irq(wled->ovp_irq); but wled->brightness, which is what the rest of the driver uses to tell whether the module is on, is left at zero. On boards where the bootloader hands the kernel a lit backlight the two disagree. MOD_EN is already set, so the interrupt is left enabled, while wled_update_status() still believes the backlight is off and takes if (!!brightness !=3D !!wled->brightness) rc =3D wled_module_enable(wled, !!brightness); on the first backlight update. wled_module_enable() then schedules wled_ovp_work(), which calls enable_irq() on the already enabled interrupt: Unbalanced enable for IRQ 176 WARNING: CPU: 0 PID: 160 at kernel/irq/manage.c:774 __enable_irq+0x50/0x80 Hardware name: Xiaomi Pocophone F1 (DT) Workqueue: events wled_ovp_work Call trace: __enable_irq+0x50/0x80 enable_irq+0x48/0xa0 wled_ovp_work+0x18/0x24 process_one_work+0x1d0/0x350 worker_thread+0x13c/0x460 kthread+0x110/0x114 ret_from_fork+0x10/0x20 The bootloader is not the only way to get there. The readback runs after wledN_setup(), and wled4_setup() sets MOD_EN itself on the path where the sink configuration does not already match, as does the tail of wled_auto_string_detection(), which all three setup paths can reach through wled_auto_detection_at_init(). A cold-booted board with a dark panel can therefore reach the same disagreement. Move the MOD_EN readback into wled_probe() and use it to seed wled->brightness, so the driver starts out agreeing with the hardware, and key the OVP interrupt off wled->brightness instead. The first backlight update then only reprograms the brightness registers and leaves both the module and the interrupt alone. The OVP interrupt also stays armed from probe whenever the module is already enabled, rather than being disabled at probe and only enabled once something writes brightness. Note that a backlight update requesting brightness 0 before any non-zero one now really does turn the module off wherever MOD_EN was already set, where before it was silently ignored. wled->brightness is seeded with default-brightness rather than the level the bootloader actually programmed, so the first update can still step the brightness. Reading that level back is version specific and is done in a follow-up, to keep this fix small enough to backport. Assisted-by: LLM Fixes: 8663c188beea ("backlight: qcom-wled: Add auto string detection logic= ") Cc: stable@vger.kernel.org Signed-off-by: David Heidelberg --- drivers/video/backlight/qcom-wled.c | 32 +++++++++++++++++++++----------- 1 file changed, 21 insertions(+), 11 deletions(-) diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/= qcom-wled.c index 22c35da72dce3..43e9f6f755582 100644 --- a/drivers/video/backlight/qcom-wled.c +++ b/drivers/video/backlight/qcom-wled.c @@ -1622,54 +1622,49 @@ static int wled_configure_short_irq(struct wled *wl= ed, =20 return rc; } =20 static int wled_configure_ovp_irq(struct wled *wled, struct platform_device *pdev) { int rc; - u32 val; =20 wled->ovp_irq =3D platform_get_irq_byname(pdev, "ovp"); if (wled->ovp_irq < 0) { dev_dbg(&pdev->dev, "OVP IRQ not found - disabling automatic string dete= ction\n"); return 0; } =20 rc =3D devm_request_threaded_irq(wled->dev, wled->ovp_irq, NULL, wled_ovp_irq_handler, IRQF_ONESHOT, "wled_ovp_irq", wled); if (rc < 0) { wled->ovp_irq =3D 0; return 0; } =20 - rc =3D regmap_read(wled->regmap, wled->ctrl_addr + - WLED3_CTRL_REG_MOD_EN, &val); - if (rc < 0) - return rc; - - /* Keep OVP irq disabled until module is enabled */ - if (!(val & WLED3_CTRL_REG_MOD_EN_MASK)) + /* Keep the OVP irq disabled until the module is enabled */ + if (!wled->brightness) disable_irq(wled->ovp_irq); =20 return 0; } =20 static const struct backlight_ops wled_ops =3D { .update_status =3D wled_update_status, }; =20 static int wled_probe(struct platform_device *pdev) { struct backlight_properties props; struct backlight_device *bl; struct wled *wled; struct regmap *regmap; + u32 mod_en; u32 val; int rc; =20 regmap =3D dev_get_regmap(pdev->dev.parent, NULL); if (!regmap) { dev_err(&pdev->dev, "Unable to get regmap\n"); return -EINVAL; } @@ -1729,27 +1724,42 @@ static int wled_probe(struct platform_device *pdev) =20 default: dev_err(wled->dev, "Invalid WLED version\n"); break; } =20 INIT_DELAYED_WORK(&wled->ovp_work, wled_ovp_work); =20 + val =3D WLED_DEFAULT_BRIGHTNESS; + of_property_read_u32(pdev->dev.of_node, "default-brightness", &val); + + /* + * The module may already be enabled, either by a bootloader that left + * the backlight lit or by the setup above. Record that, so that the + * first brightness update does not enable an already enabled module, + * and so that the OVP irq is armed from probe rather than from that + * first update. + */ + rc =3D regmap_read(wled->regmap, wled->ctrl_addr + WLED3_CTRL_REG_MOD_EN, + &mod_en); + if (rc < 0) + return rc; + + if (mod_en & WLED3_CTRL_REG_MOD_EN_MASK) + wled->brightness =3D val; + rc =3D wled_configure_short_irq(wled, pdev); if (rc < 0) return rc; =20 rc =3D wled_configure_ovp_irq(wled, pdev); if (rc < 0) return rc; =20 - val =3D WLED_DEFAULT_BRIGHTNESS; - of_property_read_u32(pdev->dev.of_node, "default-brightness", &val); - memset(&props, 0, sizeof(struct backlight_properties)); props.type =3D BACKLIGHT_RAW; props.brightness =3D val; props.max_brightness =3D wled->max_brightness; bl =3D devm_backlight_device_register(&pdev->dev, wled->name, &pdev->dev, wled, &wled_ops, &props); return PTR_ERR_OR_ZERO(bl); --=20 2.55.0 From nobody Fri Sep 25 09:22:26 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6BFD949B1E2; 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charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260914-qcom-wled-backlight-v2-3-a908d9233e93@ixit.cz> References: <20260914-qcom-wled-backlight-v2-0-a908d9233e93@ixit.cz> In-Reply-To: <20260914-qcom-wled-backlight-v2-0-a908d9233e93@ixit.cz> To: Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller , Kiran Gunda , Marco Mattiolo , =?utf-8?q?Barnab=C3=A1s_Cz=C3=A9m=C3=A1n?= Cc: linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, phone-devel@vger.kernel.org, Konrad Dybcio , Joel Selvaraj , David Heidelberg X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=6134; i=david@ixit.cz; h=from:subject:message-id; bh=69u6B8ssKSJBzJa/pOZvYchs0e6Ck19EMGhL/GRYftg=; b=owEBbQKS/ZANAwAIAWACP8TTSSByAcsmYgBqqDIcPYFb+ZX7Hi/an/rgVuWiGCmNQKNVIJIEE DiyE+yKBdSJAjMEAAEIAB0WIQTXegnP7twrvVOnBHRgAj/E00kgcgUCaqgyHAAKCRBgAj/E00kg cj8GEACDEp91oc+HGXB1DFZiXfHp/MxUIjMEyapFvq4bpJHypMEZBxkdVPYJ688U803VmyAOZKs XuN74P00jdvhi/UAaw+n3WFAq+HAZAjlEjJNYcZKIBRdxkgT58JzeNwHfjRemLCIhdUiuw8i365 daPfQz8TH+/veiT3NYjosTEdob+3oXo9vg2YanXZ5aMPOWpUwBh17/1eEA+w1fP6Wc2hDnbUGaj 4p1Wve0eM5tLGVm2xvy4s2wgTvBFxPzMwGXXhNTSXl3Pm0u4mOPTgnu904/RHtPiU4rQOVV0t8N VGTpqAqNbYSk5rfzmzuW04fCUUd4BHbA6kOiayzW7O7qiMuuyyi2yAvqlhmNowZz7R5REUfJvP/ rn8nC8DAFmzvGb5gt1eNxFMX8ImCn+DaSgnAjwIgHgmgP7QgSo/aH7qWv2vCN1AJp7qrtXFGtl4 yzqmqdwPYeQMdndzHCdmMLs4xm6o9UfILT78NhOLtHDcBhq9pW//+K16NcWXEmPh+uOP6qeJUAZ 7bUEfKuQVmFHJ+gX8cmGzIpXhb/aymQubQA69lkpH3jJSBijSXiaSl7OiUwEyxI/ZxLBIH1A8Qv degEyZvvSQj+Qlm16ztr28NGXngXUK5iKeIaZD0vcmC7LpGDncKhBW6Jg/Alc/EE9rvfCMFz7Gs DqWH94QtdcMvY8Q== X-Developer-Key: i=david@ixit.cz; a=openpgp; fpr=D77A09CFEEDC2BBD53A7047460023FC4D3492072 X-Endpoint-Received: by B4 Relay for david@ixit.cz/default with auth_id=355 X-Original-From: David Heidelberg Reply-To: david@ixit.cz From: David Heidelberg Since the previous change wled_probe() seeds wled->brightness from MOD_EN, but with default-brightness rather than the level the hardware is actually driving, so a backlight left lit by the bootloader still visibly steps on the first update, and actual_brightness reports the last value written rather than what the panel shows. Add wled_read_brightness(), which returns 0 when MOD_EN is clear and otherwise reads the brightness register the matching wledN_set_brightness() writes: the first enabled string on WLED3 and WLED4, the selected modulator on WLED5. Use it to seed both wled->brightness and the initial backlight property, and expose it as backlight_ops.get_brightness so that actual_brightness reflects the hardware too. A module that is enabled with the brightness registers at zero, which wled4_setup() and wled_auto_string_detection() can leave behind on a cold boot, now reads back as off. The OVP interrupt is then armed by the first brightness update rather than from probe, which is what happens on every other board where the module starts out disabled. Suggested-by: Konrad Dybcio Assisted-by: LLM Signed-off-by: David Heidelberg --- drivers/video/backlight/qcom-wled.c | 74 +++++++++++++++++++++++++++++++--= ---- 1 file changed, 63 insertions(+), 11 deletions(-) diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/= qcom-wled.c index 43e9f6f755582..1acb3ee86878f 100644 --- a/drivers/video/backlight/qcom-wled.c +++ b/drivers/video/backlight/qcom-wled.c @@ -285,16 +285,60 @@ static int wled5_set_brightness(struct wled *wled, u1= 6 brightness) WLED5_SINK_REG_MOD_A_BRIGHTNESS_LSB : WLED5_SINK_REG_MOD_B_BRIGHTNESS_LSB; =20 rc =3D regmap_bulk_write(wled->regmap, wled->sink_addr + offset, &v, sizeof(v)); return rc; } =20 +static int wled_read_brightness(struct wled *wled) +{ + u16 addr, mask; + __le16 v; + u32 val; + int rc; + + rc =3D regmap_read(wled->regmap, wled->ctrl_addr + WLED3_CTRL_REG_MOD_EN, + &val); + if (rc < 0) + return rc; + + if (!(val & WLED3_CTRL_REG_MOD_EN_MASK)) + return 0; + + switch (wled->version) { + case 3: + addr =3D wled->sink_addr + + WLED3_SINK_REG_BRIGHT(wled->cfg.enabled_strings[0]); + mask =3D WLED3_SINK_REG_BRIGHT_MAX; + break; + case 4: + addr =3D wled->sink_addr + + WLED4_SINK_REG_BRIGHT(wled->cfg.enabled_strings[0]); + mask =3D WLED3_SINK_REG_BRIGHT_MAX; + break; + case 5: + addr =3D wled->sink_addr + (wled->cfg.mod_sel =3D=3D MOD_A ? + WLED5_SINK_REG_MOD_A_BRIGHTNESS_LSB : + WLED5_SINK_REG_MOD_B_BRIGHTNESS_LSB); + mask =3D WLED5_SINK_REG_BRIGHT_MAX_15B; + break; + default: + dev_err(wled->dev, "Invalid WLED version\n"); + return -EINVAL; + } + + rc =3D regmap_bulk_read(wled->regmap, addr, &v, sizeof(v)); + if (rc < 0) + return rc; + + return min_t(u32, le16_to_cpu(v) & mask, wled->max_brightness); +} + static void wled_ovp_work(struct work_struct *work) { struct wled *wled =3D container_of(work, struct wled, ovp_work.work); enable_irq(wled->ovp_irq); } =20 static int wled_module_enable(struct wled *wled, int val) @@ -475,16 +519,28 @@ static int wled_update_status(struct backlight_device= *bl) wled->brightness =3D brightness; =20 unlock_mutex: mutex_unlock(&wled->lock); =20 return rc; } =20 +static int wled_get_brightness(struct backlight_device *bl) +{ + struct wled *wled =3D bl_get_data(bl); + int rc; + + mutex_lock(&wled->lock); + rc =3D wled_read_brightness(wled); + mutex_unlock(&wled->lock); + + return rc; +} + static int wled4_cabc_config(struct wled *wled, bool enable) { int i, j, rc; u8 val; =20 for (i =3D 0; i < wled->cfg.num_strings; i++) { j =3D wled->cfg.enabled_strings[i]; =20 @@ -1646,25 +1702,25 @@ static int wled_configure_ovp_irq(struct wled *wled, if (!wled->brightness) disable_irq(wled->ovp_irq); =20 return 0; } =20 static const struct backlight_ops wled_ops =3D { .update_status =3D wled_update_status, + .get_brightness =3D wled_get_brightness, }; =20 static int wled_probe(struct platform_device *pdev) { struct backlight_properties props; struct backlight_device *bl; struct wled *wled; struct regmap *regmap; - u32 mod_en; u32 val; int rc; =20 regmap =3D dev_get_regmap(pdev->dev.parent, NULL); if (!regmap) { dev_err(&pdev->dev, "Unable to get regmap\n"); return -EINVAL; } @@ -1728,41 +1784,37 @@ static int wled_probe(struct platform_device *pdev) } =20 INIT_DELAYED_WORK(&wled->ovp_work, wled_ovp_work); =20 val =3D WLED_DEFAULT_BRIGHTNESS; of_property_read_u32(pdev->dev.of_node, "default-brightness", &val); =20 /* - * The module may already be enabled, either by a bootloader that left - * the backlight lit or by the setup above. Record that, so that the - * first brightness update does not enable an already enabled module, - * and so that the OVP irq is armed from probe rather than from that - * first update. + * The module may already be lit, either by the bootloader or by the + * setup above. Start from what the hardware is driving, so that the + * first brightness update does not step the brightness. */ - rc =3D regmap_read(wled->regmap, wled->ctrl_addr + WLED3_CTRL_REG_MOD_EN, - &mod_en); + rc =3D wled_read_brightness(wled); if (rc < 0) return rc; =20 - if (mod_en & WLED3_CTRL_REG_MOD_EN_MASK) - wled->brightness =3D val; + wled->brightness =3D rc; =20 rc =3D wled_configure_short_irq(wled, pdev); if (rc < 0) return rc; =20 rc =3D wled_configure_ovp_irq(wled, pdev); if (rc < 0) return rc; =20 memset(&props, 0, sizeof(struct backlight_properties)); props.type =3D BACKLIGHT_RAW; - props.brightness =3D val; + props.brightness =3D wled->brightness ?: val; props.max_brightness =3D wled->max_brightness; bl =3D devm_backlight_device_register(&pdev->dev, wled->name, &pdev->dev, wled, &wled_ops, &props); return PTR_ERR_OR_ZERO(bl); }; =20 static void wled_remove(struct platform_device *pdev) --=20 2.55.0