lkml.org 
[lkml]   [2019]   [Feb]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC PATCH 5/5] mtd: hyperbus: Add driver for TI's Hyperbus memory controller
From
Date


On 25/02/19 9:59 PM, Sergei Shtylyov wrote:
> Hello!
>
> On 02/19/2019 09:36 AM, Vignesh R (by way of Boris Brezillon <bbrezillon@kernel.org>) wrote:
>
>> Add driver for Hyperbus memory controller on TI's AM654 SoC. Programming
>> IP is pretty simple and provides direct memory mapped access to
>> connected Flash devices.
>
> Are you sure you posted the _complete_ driver?
>


Yes, it is... You can find controller doc here[1]. Default values in the
MCR/MTR registers are good enough to simple Hyperflash access.
More perf optimization and timing optimizations will come incrementally

[1] http://www.ti.com/lit/ug/spruid7b/spruid7b.pdf 12.3.3 Hyperbus Interface

>> Add basic support for the IP without DMA. Second ChipSelect is not
>> supported for now.
>>
>> Signed-off-by: Vignesh R <vigneshr@ti.com>
>> ---
>> drivers/mtd/hyperbus/hbmc_am654.c | 105 ++++++++++++++++++++++++++++++
>> 1 file changed, 105 insertions(+)
>> create mode 100644 drivers/mtd/hyperbus/hbmc_am654.c
>>
>> diff --git a/drivers/mtd/hyperbus/hbmc_am654.c b/drivers/mtd/hyperbus/hbmc_am654.c
>> new file mode 100644
>> index 000000000000..1f0d2dc52f9f
>> --- /dev/null
>> +++ b/drivers/mtd/hyperbus/hbmc_am654.c
>> @@ -0,0 +1,105 @@
> [...]
>> +static int am654_hbmc_probe(struct platform_device *pdev)
>> +{
>> + struct device *dev = &pdev->dev;
>> + struct am654_hbmc_priv *priv;
>> + struct resource *res;
>> + int err;
>> +
>> + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
>> + if (!priv)
>> + return -ENOMEM;
>> +
>> + platform_set_drvdata(pdev, priv);
>> +
>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> + if (IS_ERR(res)) {
>> + dev_err(&pdev->dev, "failed to get memory resource\n");
>> + return -ENOENT;
>> + }
>> +
>> + priv->regbase = devm_ioremap_resource(dev, res);
>> + if (IS_ERR(priv->regbase)) {
>> + dev_err(dev, "Cannot remap controller address.\n");
>> + return PTR_ERR(priv->regbase);
>> + }
>> +
>> + pm_runtime_enable(&pdev->dev);
>> + err = pm_runtime_get_sync(&pdev->dev);
>
> That's all nice but where's the code that accesses the actual registers?

Interface and functional clk needs to be enabled even to access MMIO
space to read/write data to flash (done by the map framework). So driver
currently just enables everything during probe and disables on remove

>
>> + if (err < 0) {
>> + pm_runtime_put_noidle(&pdev->dev);
>
> Calling "put" with previously failed "get" sees strange...
>

Basically pm_runtime_get_sync() increments usage_count even in case of
failure and pm_runtime_put_noidle() puts it back. You can find many
examples of above piece of code in kernel.

>> + return err;
>> + }
>> +
>> + priv->hbdev.needs_calib = true;
>> + priv->hbdev.dev = &pdev->dev;
>> + priv->hbdev.np = of_get_next_child(dev->of_node, NULL);
>> + err = hb_register_device(&priv->hbdev);
>> + if (err) {
>> + dev_err(&pdev->dev, "failed to register controller\n");
>> + goto err_destroy;
>> + }
>> +
>> + return 0;
>> +
>> +err_destroy:
>> + hb_unregister_device(&priv->hbdev);
>
> Calling "unregister" with "register" previously failed also looks strange...
>

Agree, this is unneeded as hb_register_device() takes care of all
cleanups in err path.

>> + pm_runtime_put_sync(&pdev->dev);
>
> Why the sync() version?
>

Why not? Since the device is going away, I think its safer to ensure
device has definitely been put to idle state. I see its a common
practice in driver code.

>> + return err;
>> +}
> [...]
>
> MBR, Sergei
>

--
Regards
Vignesh

\
 
 \ /
  Last update: 2019-02-26 11:17    [W:0.294 / U:26.704 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site