linux-kernel - Re: [PATCH 3/3] DMA: PL330: Balance module remove function with probe

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Date:	Wed, 26 Sep 2012 12:11:05 +0530
From:	Inderpal Singh <inderpal.singh@...aro.org>
To:	Jassi Brar <jassisinghbrar@...il.com>
Cc:	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	boojin.kim@...sung.com, vinod.koul@...el.com, patches@...aro.org,
	kgene.kim@...sung.com
Subject: Re: [PATCH 3/3] DMA: PL330: Balance module remove function with probe

On 25 September 2012 18:47, Jassi Brar <jassisinghbrar@...il.com> wrote:
> On Tue, Sep 25, 2012 at 2:27 PM, Inderpal Singh
> <inderpal.singh@...aro.org> wrote:
>> Since peripheral channel resources are not being allocated at probe,
>> no need to flush the channels and free the resources in remove function.
>>
>> Signed-off-by: Inderpal Singh <inderpal.singh@...aro.org>
>> ---
>>  drivers/dma/pl330.c |    8 +-------
>>  1 file changed, 1 insertion(+), 7 deletions(-)
>>
>> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
>> index 04d83e6..6f06080 100644
>> --- a/drivers/dma/pl330.c
>> +++ b/drivers/dma/pl330.c
>> @@ -3012,16 +3012,10 @@ static int __devexit pl330_remove(struct amba_device *adev)
>>
>>         /* Idle the DMAC */
>>         list_for_each_entry_safe(pch, _p, &pdmac->ddma.channels,
>> -                       chan.device_node) {
>> -
>> +                       chan.device_node)
>>                 /* Remove the channel */
>>                 list_del(&pch->chan.device_node);
>>
>> -               /* Flush the channel */
>> -               pl330_control(&pch->chan, DMA_TERMINATE_ALL, 0);
>> -               pl330_free_chan_resources(&pch->chan);
>> -       }
>> -
>>         while (!list_empty(&pdmac->desc_pool)) {
>>                 desc = list_entry(pdmac->desc_pool.next,
>>                                 struct dma_pl330_desc, node);
>
> I am not sure about this patch. The DMA_TERMINATE_ALL is only called
> by the client and if the pl330 module is forced unloaded while some
> client is queued, we have to manually do DMA_TERMINATE_ALL.
> A better option could be to simply fail pl330_remove if some client is
> queued on the DMAC.
>
If we fail pl330_remove while some client is queued, the force unload
will fail and the
force unload will lose its purpose.
How about conditionally DMA_TERMINATE_ALL and free resources like below ?

@@ -3017,9 +3017,11 @@ static int __devexit pl330_remove(struct
amba_device *adev)
                /* Remove the channel */
                list_del(&pch->chan.device_node);

-               /* Flush the channel */
-               pl330_control(&pch->chan, DMA_TERMINATE_ALL, 0);
-               pl330_free_chan_resources(&pch->chan);
+               if (pch->chan.client_count != 0) {
+                       /* Flush the channel */
+                       pl330_control(&pch->chan, DMA_TERMINATE_ALL, 0);
+                       pl330_free_chan_resources(&pch->chan);
+               }
        }

        while (!list_empty(&pdmac->desc_pool)) {


Thanks,
Inder


> -jassi
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