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Message-ID: <20180503195013.GC11425@xps15>
Date: Thu, 3 May 2018 13:50:13 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Suzuki K Poulose <suzuki.poulose@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
mike.leach@...aro.org, robert.walker@....com, mark.rutland@....com,
will.deacon@....com, robin.murphy@....com, sudeep.holla@....com,
frowand.list@...il.com, robh@...nel.org, john.horley@....com
Subject: Re: [PATCH v2 07/27] coresight: tmc: Hide trace buffer handling for
file read
On Tue, May 01, 2018 at 10:10:37AM +0100, Suzuki K Poulose wrote:
> At the moment we adjust the buffer pointers for reading the trace
> data via misc device in the common code for ETF/ETB and ETR. Since
> we are going to change how we manage the buffer for ETR, let us
> move the buffer manipulation to the respective driver files, hiding
> it from the common code. We do so by adding type specific helpers
> for finding the length of data and the pointer to the buffer,
> for a given length at a file position.
>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> drivers/hwtracing/coresight/coresight-tmc-etf.c | 18 +++++++++++
> drivers/hwtracing/coresight/coresight-tmc-etr.c | 34 ++++++++++++++++++++
> drivers/hwtracing/coresight/coresight-tmc.c | 41 ++++++++++++++-----------
> drivers/hwtracing/coresight/coresight-tmc.h | 4 +++
> 4 files changed, 79 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index e2513b7..2113e93 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -120,6 +120,24 @@ static void tmc_etf_disable_hw(struct tmc_drvdata *drvdata)
> CS_LOCK(drvdata->base);
> }
>
> +/*
> + * Return the available trace data in the buffer from @pos, with
> + * a maximum limit of @len, updating the @bufpp on where to
> + * find it.
> + */
> +ssize_t tmc_etb_get_sysfs_trace(struct tmc_drvdata *drvdata,
> + loff_t pos, size_t len, char **bufpp)
> +{
> + ssize_t actual = len;
> +
> + /* Adjust the len to available size @pos */
> + if (pos + actual > drvdata->len)
> + actual = drvdata->len - pos;
> + if (actual > 0)
> + *bufpp = drvdata->buf + pos;
> + return actual;
> +}
> +
> static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev)
> {
> int ret = 0;
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index bff46f2..53a17a8 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -92,6 +92,40 @@ static void tmc_etr_enable_hw(struct tmc_drvdata *drvdata)
> CS_LOCK(drvdata->base);
> }
>
> +/*
> + * Return the available trace data in the buffer @pos, with a maximum
> + * limit of @len, also updating the @bufpp on where to find it.
> + */
> +ssize_t tmc_etr_get_sysfs_trace(struct tmc_drvdata *drvdata,
> + loff_t pos, size_t len, char **bufpp)
> +{
> + ssize_t actual = len;
> + char *bufp = drvdata->buf + pos;
> + char *bufend = (char *)(drvdata->vaddr + drvdata->size);
> +
> + /* Adjust the len to available size @pos */
> + if (pos + actual > drvdata->len)
> + actual = drvdata->len - pos;
> +
> + if (actual <= 0)
> + return actual;
> +
> + /*
> + * Since we use a circular buffer, with trace data starting
> + * @drvdata->buf, possibly anywhere in the buffer @drvdata->vaddr,
> + * wrap the current @pos to within the buffer.
> + */
> + if (bufp >= bufend)
> + bufp -= drvdata->size;
> + /*
> + * For simplicity, avoid copying over a wrapped around buffer.
> + */
> + if ((bufp + actual) > bufend)
> + actual = bufend - bufp;
> + *bufpp = bufp;
> + return actual;
> +}
> +
> static void tmc_etr_dump_hw(struct tmc_drvdata *drvdata)
> {
> const u32 *barrier;
> diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
> index 0ea04f5..7a4e84f 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc.c
> @@ -131,35 +131,40 @@ static int tmc_open(struct inode *inode, struct file *file)
> return 0;
> }
>
> +static inline ssize_t tmc_get_sysfs_trace(struct tmc_drvdata *drvdata,
> + loff_t pos, size_t len, char **bufpp)
> +{
> + switch (drvdata->config_type) {
> + case TMC_CONFIG_TYPE_ETB:
> + case TMC_CONFIG_TYPE_ETF:
> + return tmc_etb_get_sysfs_trace(drvdata, pos, len, bufpp);
> + case TMC_CONFIG_TYPE_ETR:
> + return tmc_etr_get_sysfs_trace(drvdata, pos, len, bufpp);
> + }
> +
> + return -EINVAL;
Extra space betwen return and -EINVAL.
> +}
> +
> static ssize_t tmc_read(struct file *file, char __user *data, size_t len,
> loff_t *ppos)
> {
> + char *bufp;
> + ssize_t actual;
> struct tmc_drvdata *drvdata = container_of(file->private_data,
> struct tmc_drvdata, miscdev);
> - char *bufp = drvdata->buf + *ppos;
> + actual = tmc_get_sysfs_trace(drvdata, *ppos, len, &bufp);
> + if (actual <= 0)
> + return 0;
>
> - if (*ppos + len > drvdata->len)
> - len = drvdata->len - *ppos;
> -
> - if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) {
> - if (bufp == (char *)(drvdata->vaddr + drvdata->size))
> - bufp = drvdata->vaddr;
> - else if (bufp > (char *)(drvdata->vaddr + drvdata->size))
> - bufp -= drvdata->size;
> - if ((bufp + len) > (char *)(drvdata->vaddr + drvdata->size))
> - len = (char *)(drvdata->vaddr + drvdata->size) - bufp;
> - }
> -
> - if (copy_to_user(data, bufp, len)) {
> + if (copy_to_user(data, bufp, actual)) {
> dev_dbg(drvdata->dev, "%s: copy_to_user failed\n", __func__);
> return -EFAULT;
> }
>
> - *ppos += len;
> + *ppos += actual;
> + dev_dbg(drvdata->dev, "%zu bytes copied\n", actual);
>
> - dev_dbg(drvdata->dev, "%s: %zu bytes copied, %d bytes left\n",
> - __func__, len, (int)(drvdata->len - *ppos));
> - return len;
> + return actual;
> }
>
> static int tmc_release(struct inode *inode, struct file *file)
> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
> index cdff853..9cbc4d5 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.h
> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> @@ -184,10 +184,14 @@ int tmc_read_unprepare_etb(struct tmc_drvdata *drvdata);
> extern const struct coresight_ops tmc_etb_cs_ops;
> extern const struct coresight_ops tmc_etf_cs_ops;
>
> +ssize_t tmc_etb_get_sysfs_trace(struct tmc_drvdata *drvdata,
> + loff_t pos, size_t len, char **bufpp);
> /* ETR functions */
> int tmc_read_prepare_etr(struct tmc_drvdata *drvdata);
> int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata);
> extern const struct coresight_ops tmc_etr_cs_ops;
> +ssize_t tmc_etr_get_sysfs_trace(struct tmc_drvdata *drvdata,
> + loff_t pos, size_t len, char **bufpp);
>
>
> #define TMC_REG_PAIR(name, lo_off, hi_off) \
> --
> 2.7.4
>
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