From 9aadd70aed60b47e367e7a1a6b9068daba04fe05 Mon Sep 17 00:00:00 2001 From: Paul Walmsley Date: Tue, 6 Nov 2012 16:31:32 +0000 Subject: Revert "ARM: OMAP: convert I2C driver to PM QoS for MPU latency constraints" This reverts commit 3db11feffc1ad2ab9dea27789e6b5b3032827adc (ARM: OMAP: convert I2C driver to PM QoS for MPU latency constraints). This commit causes I2C timeouts to appear on several OMAP3430/3530-based boards: http://marc.info/?l=linux-arm-kernel&m=135071372426971&w=2 http://marc.info/?l=linux-arm-kernel&m=135067558415214&w=2 http://marc.info/?l=linux-arm-kernel&m=135216013608196&w=2 and appears to have been sent for merging before one of its prerequisites was merged: http://marc.info/?l=linux-arm-kernel&m=135219411617621&w=2 Signed-off-by: Paul Walmsley Acked-by: Jean Pihet Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-omap.c | 32 ++++++++++++++------------------ 1 file changed, 14 insertions(+), 18 deletions(-) (limited to 'drivers/i2c/busses/i2c-omap.c') diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c index db31eaed6ea5..0b0254312d21 100644 --- a/drivers/i2c/busses/i2c-omap.c +++ b/drivers/i2c/busses/i2c-omap.c @@ -43,7 +43,6 @@ #include #include #include -#include /* I2C controller revisions */ #define OMAP_I2C_OMAP1_REV_2 0x20 @@ -187,8 +186,9 @@ struct omap_i2c_dev { int reg_shift; /* bit shift for I2C register addresses */ struct completion cmd_complete; struct resource *ioarea; - u32 latency; /* maximum MPU wkup latency */ - struct pm_qos_request pm_qos_request; + u32 latency; /* maximum mpu wkup latency */ + void (*set_mpu_wkup_lat)(struct device *dev, + long latency); u32 speed; /* Speed of bus in kHz */ u32 dtrev; /* extra revision from DT */ u32 flags; @@ -494,7 +494,9 @@ static void omap_i2c_resize_fifo(struct omap_i2c_dev *dev, u8 size, bool is_rx) dev->b_hw = 1; /* Enable hardware fixes */ /* calculate wakeup latency constraint for MPU */ - dev->latency = (1000000 * dev->threshold) / (1000 * dev->speed / 8); + if (dev->set_mpu_wkup_lat != NULL) + dev->latency = (1000000 * dev->threshold) / + (1000 * dev->speed / 8); } /* @@ -629,16 +631,8 @@ omap_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num) if (r < 0) goto out; - /* - * When waiting for completion of a i2c transfer, we need to - * set a wake up latency constraint for the MPU. This is to - * ensure quick enough wakeup from idle, when transfer - * completes. - */ - if (dev->latency) - pm_qos_add_request(&dev->pm_qos_request, - PM_QOS_CPU_DMA_LATENCY, - dev->latency); + if (dev->set_mpu_wkup_lat != NULL) + dev->set_mpu_wkup_lat(dev->dev, dev->latency); for (i = 0; i < num; i++) { r = omap_i2c_xfer_msg(adap, &msgs[i], (i == (num - 1))); @@ -646,8 +640,8 @@ omap_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num) break; } - if (dev->latency) - pm_qos_remove_request(&dev->pm_qos_request); + if (dev->set_mpu_wkup_lat != NULL) + dev->set_mpu_wkup_lat(dev->dev, -1); if (r == 0) r = num; @@ -1104,6 +1098,7 @@ omap_i2c_probe(struct platform_device *pdev) } else if (pdata != NULL) { dev->speed = pdata->clkrate; dev->flags = pdata->flags; + dev->set_mpu_wkup_lat = pdata->set_mpu_wkup_lat; dev->dtrev = pdata->rev; } @@ -1159,8 +1154,9 @@ omap_i2c_probe(struct platform_device *pdev) dev->b_hw = 1; /* Enable hardware fixes */ /* calculate wakeup latency constraint for MPU */ - dev->latency = (1000000 * dev->fifo_size) / - (1000 * dev->speed / 8); + if (dev->set_mpu_wkup_lat != NULL) + dev->latency = (1000000 * dev->fifo_size) / + (1000 * dev->speed / 8); } /* reset ASAP, clearing any IRQs */ -- cgit v1.2.1 From aedc256dd032fe9b0691fdd0f67b5e65e3e7bc0d Mon Sep 17 00:00:00 2001 From: Felipe Balbi Date: Wed, 14 Nov 2012 16:22:45 +0200 Subject: i2c: omap: ensure writes to dev->buf_len are ordered if we allow compiler reorder our writes, we could fall into a situation where dev->buf_len is reset for no apparent reason. This bug was found with a simple script which would transfer data to an i2c client from 1 to 1024 bytes (a simple for loop), when we got to transfer sizes bigger than the fifo size, dev->buf_len was reset to zero before we had an oportunity to handle XDR Interrupt. Because dev->buf_len was zero, we entered omap_i2c_transmit_data() to transfer zero bytes, which would mean we would just silently exit omap_i2c_transmit_data() without actually writing anything to DATA register. That would cause XDR IRQ to trigger forever and we would never transfer the remaining bytes. After adding the memory barrier, we also drop resetting dev->buf_len to zero in omap_i2c_xfer_msg() because both omap_i2c_transmit_data() and omap_i2c_receive_data() will act until dev->buf_len reaches zero, rendering the other write in omap_i2c_xfer_msg() redundant. This patch has been tested with pandaboard for a few iterations of the script mentioned above. Signed-off-by: Felipe Balbi Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-omap.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'drivers/i2c/busses/i2c-omap.c') diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c index 0b0254312d21..3525c9e62cb0 100644 --- a/drivers/i2c/busses/i2c-omap.c +++ b/drivers/i2c/busses/i2c-omap.c @@ -524,6 +524,9 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap, dev->buf = msg->buf; dev->buf_len = msg->len; + /* make sure writes to dev->buf_len are ordered */ + barrier(); + omap_i2c_write_reg(dev, OMAP_I2C_CNT_REG, dev->buf_len); /* Clear the FIFO Buffers */ @@ -581,7 +584,6 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap, */ timeout = wait_for_completion_timeout(&dev->cmd_complete, OMAP_I2C_TIMEOUT); - dev->buf_len = 0; if (timeout == 0) { dev_err(dev->dev, "controller timed out\n"); omap_i2c_init(dev); -- cgit v1.2.1