mbox series

[v2,0/3] soc: qcom: rmtfs: Support dynamic allocation

Message ID 20230530233643.4044823-1-quic_bjorande@quicinc.com
Headers show
Series soc: qcom: rmtfs: Support dynamic allocation | expand

Message

Bjorn Andersson May 30, 2023, 11:36 p.m. UTC 
Some platforms have laxed requirements on the placement of the rmtfs
memory region, introduce support for guard pages to allow the DeviceTree
author to rely on the OS/Linux for placement of the region.

Bjorn Andersson (3):
  dt-bindings: reserved-memory: rmtfs: Allow guard pages
  soc: qcom: rmtfs: Support discarding guard pages
  soc: qcom: rtmfs: Handle reserved-memory allocation issues

 .../bindings/reserved-memory/qcom,rmtfs-mem.yaml     |  7 +++++++
 drivers/soc/qcom/rmtfs_mem.c                         | 12 +++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

Comments

Caleb Connolly May 31, 2023, 12:09 a.m. UTC | #1 
On 31/05/2023 01:08, Caleb Connolly wrote:
> 
> 
> On 31/05/2023 00:36, Bjorn Andersson wrote:
>> In some configurations, the exact placement of the rmtfs shared memory
>> region isn't so strict. The DeviceTree author can then choose to use the
>> "size" property and rely on the OS for placement (in combination with
>> "alloc-ranges", if desired).
>>
>> But on some platforms the rmtfs memory region may not be allocated
>> adjacent to regions allocated by other clients. Add support for
>> discarding the first and last 4k block in the region, if
>> qcom,use-guard-pages is specified in DeviceTree.
> 
> Oh nice!
... Bit eager on the enter key there
>>
>> Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>

Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
>> ---
>>
>> Changes since v1:
>> - Drop the dma_alloc_coherent() based approach and just add support for
>>   the guard pages.
>>
>>  drivers/soc/qcom/rmtfs_mem.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/soc/qcom/rmtfs_mem.c b/drivers/soc/qcom/rmtfs_mem.c
>> index f83811f51175..28238974d913 100644
>> --- a/drivers/soc/qcom/rmtfs_mem.c
>> +++ b/drivers/soc/qcom/rmtfs_mem.c
>> @@ -213,6 +213,16 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
>>  		goto put_device;
>>  	}
>>  
>> +	/*
>> +	 * If requested, discard the first and last 4k block in order to ensure
>> +	 * that the rmtfs region isn't adjacent to other protected regions.
>> +	 */
>> +	if (of_property_present(node, "qcom,use-guard-pages")) {
>> +		rmtfs_mem->addr += SZ_4K;
>> +		rmtfs_mem->base += SZ_4K;
>> +		rmtfs_mem->size -= 2 * SZ_4K;
>> +	}
>> +
>>  	cdev_init(&rmtfs_mem->cdev, &qcom_rmtfs_mem_fops);
>>  	rmtfs_mem->cdev.owner = THIS_MODULE;
>>  
>
Stephan Gerhold June 1, 2023, 12:26 p.m. UTC | #2 
On Tue, May 30, 2023 at 04:36:42PM -0700, Bjorn Andersson wrote:
> In some configurations, the exact placement of the rmtfs shared memory
> region isn't so strict. The DeviceTree author can then choose to use the
> "size" property and rely on the OS for placement (in combination with
> "alloc-ranges", if desired).
> 
> But on some platforms the rmtfs memory region may not be allocated
> adjacent to regions allocated by other clients. Add support for
> discarding the first and last 4k block in the region, if
> qcom,use-guard-pages is specified in DeviceTree.
> 
> Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
> ---
> 
> Changes since v1:
> - Drop the dma_alloc_coherent() based approach and just add support for
>   the guard pages.
> 
>  drivers/soc/qcom/rmtfs_mem.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/soc/qcom/rmtfs_mem.c b/drivers/soc/qcom/rmtfs_mem.c
> index f83811f51175..28238974d913 100644
> --- a/drivers/soc/qcom/rmtfs_mem.c
> +++ b/drivers/soc/qcom/rmtfs_mem.c
> @@ -213,6 +213,16 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
>  		goto put_device;
>  	}
>  
> +	/*
> +	 * If requested, discard the first and last 4k block in order to ensure
> +	 * that the rmtfs region isn't adjacent to other protected regions.
> +	 */
> +	if (of_property_present(node, "qcom,use-guard-pages")) {
> +		rmtfs_mem->addr += SZ_4K;
> +		rmtfs_mem->base += SZ_4K;
> +		rmtfs_mem->size -= 2 * SZ_4K;
> +	}

It probably doesn't make a big difference in practice but I would say
there is no need to even memremap() the guard pages. If you adjust the
->addr and ->size before the memremap() then you don't need to modify
the ->base at all.

Thanks,
Stephan