Re: [PATCH v1 1/3] dmaengine: dmatest: Fix regression when run command on misconfigured channel

Vinod Koul
2020-09-17T10:31:34Z

HI Andy/Vladimir
On 16-09-20, 16:34, Andy Shevchenko wrote:
> From: Vladimir Murzin <vladimir.murzin@arm.com>

Subject of the patch is not apt. It describes the effect of this patch,
which is to fix the regression but does not describe the change. Please
revise it to describe the change done in this patch

> Andy reported that commit 6b41030fdc79 ("dmaengine: dmatest:
> Restore default for channel") broke his scripts for the case
> where "busy" channel is used for configuration with expectation
> that run command would do nothing (and return 0). Instead,
> behavior was (unintentionally) changed to treat such case as
> under-configuration and progress with defaults, i.e. run command
> would start a test with default setting for channel (which would
> use all channels).

but a mis-configured channel returning success and doing nothing does
not look as a good behaviour, I agree it broke Andy's script but the
behaviour was not good to start with ;)

> Restore original behavior with tracking status of channel setter
> so we can distinguish between misconfigured and under-configured
> cases in run command and act accordingly.
>
> Fixes: 6b41030fdc79 ("dmaengine: dmatest: Restore default for channel")
> Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> drivers/dma/dmatest.c | 28 ++++++++++++++++++++++------
> 1 file changed, 22 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
> index b2790641370a..4c9a9d7b48bb 100644
> --- a/drivers/dma/dmatest.c
> +++ b/drivers/dma/dmatest.c
> @@ -129,6 +129,7 @@ struct dmatest_params {
> * @nr_channels: number of channels under test
> * @lock: access protection to the fields of this structure
> * @did_init: module has been initialized completely
> + * @last_error: test has faced configuration issues
> */
> static struct dmatest_info {
> /* Test parameters */
> @@ -137,6 +138,7 @@ static struct dmatest_info {
> /* Internal state */
> struct list_head channels;
> unsigned int nr_channels;
> + int last_error;
> struct mutex lock;
> bool did_init;
> } test_info = {
> @@ -1202,10 +1204,22 @@ static int dmatest_run_set(const char *val, const struct kernel_param *kp)
> return ret;
> } else if (dmatest_run) {
> if (!is_threaded_test_pending(info)) {
> - pr_info("No channels configured, continue with any\n");
> - if (!is_threaded_test_run(info))
> - stop_threaded_test(info);
> - add_threaded_test(info);
> + /*
> + * We have nothing to run. This can be due to:
> + */
> + ret = info->last_error;
> + if (ret) {
> + /* 1) Mis-configuration */
> + pr_warn("Channel misconfigured, can't continue\n");

I would think this should be error

> + mutex_unlock(&info->lock);
> + return ret;
> + } else {
> + /* 2) We rely on defaults */
> + pr_info("No channels configured, continue with any\n");
> + if (!is_threaded_test_run(info))
> + stop_threaded_test(info);
> + add_threaded_test(info);
> + }
> }
> start_threaded_tests(info);
> } else {
> @@ -1222,7 +1236,7 @@ static int dmatest_chan_set(const char *val, const struct kernel_param *kp)
> struct dmatest_info *info = &test_info;
> struct dmatest_chan *dtc;
> char chan_reset_val[20];
> - int ret = 0;
> + int ret;

Does this belong to this fix?

>
> mutex_lock(&info->lock);
> ret = param_set_copystring(val, kp);
> @@ -1230,7 +1244,7 @@ static int dmatest_chan_set(const char *val, const struct kernel_param *kp)
> mutex_unlock(&info->lock);
> return ret;
> }
> - /*Clear any previously run threads */
> + /* Clear any previously run threads */

Lets keep style issues away from fixes please

> if (!is_threaded_test_run(info) && !is_threaded_test_pending(info))
> stop_threaded_test(info);
> /* Reject channels that are already registered */
> @@ -1277,12 +1291,14 @@ static int dmatest_chan_set(const char *val, const struct kernel_param *kp)
> goto add_chan_err;
> }
>
> + info->last_error = ret;
> mutex_unlock(&info->lock);
>
> return ret;
>
> add_chan_err:
> param_set_copystring(chan_reset_val, kp);
> + info->last_error = ret;
> mutex_unlock(&info->lock);
>
> return ret;
> --
> 2.28.0

--
~Vinod