18 Nov
2019
18 Nov
'19
8:49 p.m.
On Mon, 18 Nov 2019 20:20:41 +0100, Sridharan, Ranjani wrote:
On Mon, Nov 18, 2019 at 10:54 AM Takashi Iwai tiwai@suse.de wrote:
On Mon, 18 Nov 2019 17:38:49 +0100, Pierre-Louis Bossart wrote: > > > > On 11/17/19 2:53 AM, Takashi Iwai wrote: > > Many PCI and other drivers performs snd_pcm_period_elapsed() simply in > > its interrupt handler, so the sync_stop operation is just to call > > synchronize_irq(). Instead of putting this call multiple times, > > introduce the common card->sync_irq field. When this field is set, > > PCM core performs synchronize_irq() for sync-stop operation. Each > > driver just needs to copy its local IRQ number to card->sync_irq, and > > that's all we need. > > Maybe a red-herring or complete non-sense, but I wonder if this is > going to get in the way of Ranjani's multi-client work, where we could > have multiple cards created but with a single IRQ handled by the > parent PCI device? > > Ranjani, you may want to double-check this and chime in, thanks! The synchronize_irq() is fairly safe to call multiple times, and I don't think any problem by invoking it for multi-clients sharing the same IRQ. For example, Digigram miXart driver creates multiple card objects from a single PCI entry, and I already thought of that possibility; they set the same card->sync_irq value to all card objects, which eventually will call synchronize_irq() multiple times. From the performance POV, this shouldn't be a big problem, because the place calling this is only at hw_params, prepare and hw_free, neither are hot-path.Thanks for the clarification, Takashi. But just wondering how would one pass on the sync_irq when the snd_card is created? Typically in the case of the Intel platforms, the card->dev points to the platform device for the machine driver that registers the card and the PCI device is the parent of the machine drv platform device.
It's completely up to the driver implementation :) You can implement the own sync_stop ops if that's easier, too.
In general, the driver can set up card->sync_irq when the request_irq() or its variant is called.
Takashi