From b20566cdef05cd40d95f10869d2a7646f48b1bbe Mon Sep 17 00:00:00 2001 From: Douglas Anderson Date: Thu, 26 Jan 2023 17:09:12 -0800 Subject: drm/msm/dp: Clean up handling of DP AUX interrupts The DP AUX interrupt handling was a bit of a mess. * There were two functions (one for "native" transfers and one for "i2c" transfers) that were quite similar. It was hard to say how many of the differences between the two functions were on purpose and how many of them were just an accident of how they were coded. * Each function sometimes used "else if" to test for error bits and sometimes didn't and again it was hard to say if this was on purpose or just an accident. * The two functions wouldn't notice whether "unknown" bits were set. For instance, there seems to be a bit "DP_INTR_PLL_UNLOCKED" and if it was set there would be no indication. * The two functions wouldn't notice if more than one error was set. Let's fix this by being more consistent / explicit about what we're doing. By design this could cause different handling for AUX transfers, though I'm not actually aware of any bug fixed as a result of this patch (this patch was created because we simply noticed how odd the old code was by code inspection). Specific notes here: 1. In the old native transfer case if we got "done + wrong address" we'd ignore the "wrong address" (because of the "else if"). Now we won't. 2. In the old native transfer case if we got "done + timeout" we'd ignore the "timeout" (because of the "else if"). Now we won't. 3. In the old native transfer case we'd see "nack_defer" and translate it to the error number for "nack". This differed from the i2c transfer case where "nack_defer" was given the error number for "nack_defer". This 100% can't matter because the only user of this error number treats "nack defer" the same as "nack", so it's clear that the difference between the "native" and "i2c" was pointless here. 4. In the old i2c transfer case if we got "done" plus any error besides "nack" or "defer" then we'd ignore the error. Now we don't. 5. If there is more than one error signaled by the hardware it's possible that we'll report a different one than we used to. I don't know if this matters. If someone is aware of a case this matters we should document it and change the code to make it explicit. 6. One quirk we keep (I don't know if this is important) is that in the i2c transfer case if we see "done + defer" we report that as a "nack". That seemed too intentional in the old code to just drop. After this change we will add extra logging, including: * A warning if we see more than one error bit set. * A warning if we see an unexpected interrupt. * A warning if we get an AUX transfer interrupt when shouldn't. It actually turns out that as a result of this change then at boot we sometimes see an error: [drm:dp_aux_isr] *ERROR* Unexpected DP AUX IRQ 0x01000000 when not busy That means that, during init, we are seeing DP_INTR_PLL_UNLOCKED. For now I'm going to say that leaving this error reported in the logs is OK-ish and hopefully it will encourage someone to track down what's going on at init time. One last note here is that this change renames one of the interrupt bits. The bit named "i2c done" clearly was used for native transfers being done too, so I renamed it to indicate this. Signed-off-by: Douglas Anderson Tested-by: Kuogee Hsieh Reviewed-by: Kuogee Hsieh Patchwork: https://patchwork.freedesktop.org/patch/520658/ Link: https://lore.kernel.org/r/20230126170745.v2.1.I90ffed3ddd21e818ae534f820cb4d6d8638859ab@changeid Signed-off-by: Dmitry Baryshkov --- drivers/gpu/drm/msm/dp/dp_aux.c | 80 ++++++++++++++++++----------------------- 1 file changed, 34 insertions(+), 46 deletions(-) (limited to 'drivers/gpu/drm/msm/dp/dp_aux.c') diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c b/drivers/gpu/drm/msm/dp/dp_aux.c index cc3efed593aa..84f9e3e5f964 100644 --- a/drivers/gpu/drm/msm/dp/dp_aux.c +++ b/drivers/gpu/drm/msm/dp/dp_aux.c @@ -162,47 +162,6 @@ static ssize_t dp_aux_cmd_fifo_rx(struct dp_aux_private *aux, return i; } -static void dp_aux_native_handler(struct dp_aux_private *aux, u32 isr) -{ - if (isr & DP_INTR_AUX_I2C_DONE) - aux->aux_error_num = DP_AUX_ERR_NONE; - else if (isr & DP_INTR_WRONG_ADDR) - aux->aux_error_num = DP_AUX_ERR_ADDR; - else if (isr & DP_INTR_TIMEOUT) - aux->aux_error_num = DP_AUX_ERR_TOUT; - if (isr & DP_INTR_NACK_DEFER) - aux->aux_error_num = DP_AUX_ERR_NACK; - if (isr & DP_INTR_AUX_ERROR) { - aux->aux_error_num = DP_AUX_ERR_PHY; - dp_catalog_aux_clear_hw_interrupts(aux->catalog); - } -} - -static void dp_aux_i2c_handler(struct dp_aux_private *aux, u32 isr) -{ - if (isr & DP_INTR_AUX_I2C_DONE) { - if (isr & (DP_INTR_I2C_NACK | DP_INTR_I2C_DEFER)) - aux->aux_error_num = DP_AUX_ERR_NACK; - else - aux->aux_error_num = DP_AUX_ERR_NONE; - } else { - if (isr & DP_INTR_WRONG_ADDR) - aux->aux_error_num = DP_AUX_ERR_ADDR; - else if (isr & DP_INTR_TIMEOUT) - aux->aux_error_num = DP_AUX_ERR_TOUT; - if (isr & DP_INTR_NACK_DEFER) - aux->aux_error_num = DP_AUX_ERR_NACK_DEFER; - if (isr & DP_INTR_I2C_NACK) - aux->aux_error_num = DP_AUX_ERR_NACK; - if (isr & DP_INTR_I2C_DEFER) - aux->aux_error_num = DP_AUX_ERR_DEFER; - if (isr & DP_INTR_AUX_ERROR) { - aux->aux_error_num = DP_AUX_ERR_PHY; - dp_catalog_aux_clear_hw_interrupts(aux->catalog); - } - } -} - static void dp_aux_update_offset_and_segment(struct dp_aux_private *aux, struct drm_dp_aux_msg *input_msg) { @@ -427,13 +386,42 @@ void dp_aux_isr(struct drm_dp_aux *dp_aux) if (!isr) return; - if (!aux->cmd_busy) + if (!aux->cmd_busy) { + DRM_ERROR("Unexpected DP AUX IRQ %#010x when not busy\n", isr); return; + } - if (aux->native) - dp_aux_native_handler(aux, isr); - else - dp_aux_i2c_handler(aux, isr); + /* + * The logic below assumes only one error bit is set (other than "done" + * which can apparently be set at the same time as some of the other + * bits). Warn if more than one get set so we know we need to improve + * the logic. + */ + if (hweight32(isr & ~DP_INTR_AUX_XFER_DONE) > 1) + DRM_WARN("Some DP AUX interrupts unhandled: %#010x\n", isr); + + if (isr & DP_INTR_AUX_ERROR) { + aux->aux_error_num = DP_AUX_ERR_PHY; + dp_catalog_aux_clear_hw_interrupts(aux->catalog); + } else if (isr & DP_INTR_NACK_DEFER) { + aux->aux_error_num = DP_AUX_ERR_NACK_DEFER; + } else if (isr & DP_INTR_WRONG_ADDR) { + aux->aux_error_num = DP_AUX_ERR_ADDR; + } else if (isr & DP_INTR_TIMEOUT) { + aux->aux_error_num = DP_AUX_ERR_TOUT; + } else if (!aux->native && (isr & DP_INTR_I2C_NACK)) { + aux->aux_error_num = DP_AUX_ERR_NACK; + } else if (!aux->native && (isr & DP_INTR_I2C_DEFER)) { + if (isr & DP_INTR_AUX_XFER_DONE) + aux->aux_error_num = DP_AUX_ERR_NACK; + else + aux->aux_error_num = DP_AUX_ERR_DEFER; + } else if (isr & DP_INTR_AUX_XFER_DONE) { + aux->aux_error_num = DP_AUX_ERR_NONE; + } else { + DRM_WARN("Unexpected interrupt: %#010x\n", isr); + return; + } complete(&aux->comp); } -- cgit From bfc12020e63d017ea8f85cda9c39cbd1314ecd77 Mon Sep 17 00:00:00 2001 From: Douglas Anderson Date: Thu, 26 Jan 2023 17:09:13 -0800 Subject: drm/msm/dp: Return IRQ_NONE for unhandled interrupts If our interrupt handler gets called and we don't really handle the interrupt then we should return IRQ_NONE. The current interrupt handler didn't do this, so let's fix it. NOTE: for some of the cases it's clear that we should return IRQ_NONE and some cases it's clear that we should return IRQ_HANDLED. However, there are a few that fall somewhere in between. Specifically, the documentation for when to return IRQ_NONE vs. IRQ_HANDLED is probably best spelled out in the commit message of commit d9e4ad5badf4 ("Document that IRQ_NONE should be returned when IRQ not actually handled"). That commit makes it clear that we should return IRQ_HANDLED if we've done something to make the interrupt stop happening. The case where it's unclear is, for instance, in dp_aux_isr() after we've read the interrupt using dp_catalog_aux_get_irq() and confirmed that "isr" is non-zero. The function dp_catalog_aux_get_irq() not only reads the interrupts but it also "ack"s all the interrupts that are returned. For an "unknown" interrupt this has a very good chance of actually stopping the interrupt from happening. That would mean we've identified that it's our device and done something to stop them from happening and should return IRQ_HANDLED. Specifically, it should be noted that most interrupts that need "ack"ing are ones that are one-time events and doing an "ack" is enough to clear them. However, since these interrupts are unknown then, by definition, it's unknown if "ack"ing them is truly enough to clear them. It's possible that we also need to remove the original source of the interrupt. In this case, IRQ_NONE would be a better choice. Given that returning an occasional IRQ_NONE isn't the absolute end of the world, however, let's choose that course of action. The IRQ framework will forgive a few IRQ_NONE returns now and again (and it won't even log them, which is why we have to log them ourselves). This means that if we _do_ end hitting an interrupt where "ack"ing isn't enough the kernel will eventually detect the problem and shut our device down. Signed-off-by: Douglas Anderson Tested-by: Kuogee Hsieh Reviewed-by: Kuogee Hsieh Patchwork: https://patchwork.freedesktop.org/patch/520660/ Link: https://lore.kernel.org/r/20230126170745.v2.2.I2d7aec2fadb9c237cd0090a47d6a8ba2054bf0f8@changeid [DB: reformatted commit message to make checkpatch happy] Signed-off-by: Dmitry Baryshkov --- drivers/gpu/drm/msm/dp/dp_aux.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'drivers/gpu/drm/msm/dp/dp_aux.c') diff --git a/drivers/gpu/drm/msm/dp/dp_aux.c b/drivers/gpu/drm/msm/dp/dp_aux.c index 84f9e3e5f964..8e3b677f35e6 100644 --- a/drivers/gpu/drm/msm/dp/dp_aux.c +++ b/drivers/gpu/drm/msm/dp/dp_aux.c @@ -368,14 +368,14 @@ exit: return ret; } -void dp_aux_isr(struct drm_dp_aux *dp_aux) +irqreturn_t dp_aux_isr(struct drm_dp_aux *dp_aux) { u32 isr; struct dp_aux_private *aux; if (!dp_aux) { DRM_ERROR("invalid input\n"); - return; + return IRQ_NONE; } aux = container_of(dp_aux, struct dp_aux_private, dp_aux); @@ -384,11 +384,11 @@ void dp_aux_isr(struct drm_dp_aux *dp_aux) /* no interrupts pending, return immediately */ if (!isr) - return; + return IRQ_NONE; if (!aux->cmd_busy) { DRM_ERROR("Unexpected DP AUX IRQ %#010x when not busy\n", isr); - return; + return IRQ_NONE; } /* @@ -420,10 +420,12 @@ void dp_aux_isr(struct drm_dp_aux *dp_aux) aux->aux_error_num = DP_AUX_ERR_NONE; } else { DRM_WARN("Unexpected interrupt: %#010x\n", isr); - return; + return IRQ_NONE; } complete(&aux->comp); + + return IRQ_HANDLED; } void dp_aux_reconfig(struct drm_dp_aux *dp_aux) -- cgit