From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jakub =?UTF-8?B?S2ljacWEc2tp?= Subject: Re: [PATCH v4 2/2] serial/amba-pl011: Refactor and simplify TX FIFO handling Date: Mon, 30 Mar 2015 16:28:11 +0200 Message-ID: <20150330162811.3673482b@north> References: <1427468371-11915-1-git-send-email-Dave.Martin@arm.com> <1427468371-11915-3-git-send-email-Dave.Martin@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <1427468371-11915-3-git-send-email-Dave.Martin@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Dave Martin Cc: Russell King , Greg Kroah-Hartman , Andrew Jackson , Graeme Gregory , linux-serial@vger.kernel.org, Andre Przywara , popcorn mix , Jorge Ramirez-Ortiz , linux-arm-kernel@lists.infradead.org List-Id: linux-serial@vger.kernel.org T24gRnJpLCAyNyBNYXIgMjAxNSAxNDo1OTozMSArMDAwMCwgRGF2ZSBNYXJ0aW4gd3JvdGU6Cj4g Q29tbWl0IDczNDc0NWMgc2VyaWFsL2FtYmEtcGwwMTE6IEFjdGl2YXRlIFRYIElSUSBwYXNzaXZl bHkKPiBhZGRzIHNvbWUgdW5uZWNlc3NhcnkgY29tcGxleGl0eSBhbmQgb3ZlcmhlYWQgaW4gdGhl IGZvcm0gb2YKPiBhIHNvZnRpcnEgbWVjaGFuaXNtIGZvciB0cmFuc21pdHRpbmcgaW4gdGhlIGFi c2VuY2Ugb2YgaW50ZXJydXB0cy4KPiAKPiBBZnRlciBzb21lIGRpc2N1c3Npb24gWzFdLCB0aGlz IHR1cm5zIG91dCB0byBiZSB1bm5lY2Vzc2FyeS4KPiAKPiBUaGlzIHBhdGNoIHNpbXBsaWZpZXMg dGhlIGNvZGUgZmxvdyB0byByZWR1Y2UgdGhlIHJlbGlhbmNlIG9uCj4gc3VidGxlIGJlaGF2aW91 ciBhbmQgYXZvaWQgZnJhZ2lsaXR5IHVuZGVyIGZ1dHVyZSBtYWludGVuYW5jZS4KPiAKPiBUbyB0 aGlzIGVuZCwgdGhlIFRYIHNvZnRpcnEgbWVjaGFuaXNtIGlzIHJlbW92ZWQgYW5kIGluc3RlYWQK PiBwbDAxMV9zdGFydF90eCgpIHdpbGwgbm93IHNpbXBseSBzdHVmZiB0aGUgRklGTyB1bnRpbCBm dWxsCj4gKGd1YXJhbnRlZWluZyBmdXR1cmUgVFggSVJRcyksIG9yIHVudGlsIHRoZXJlIGFyZSBu byBtb3JlIGNoYXJzCj4gdG8gd3JpdGUgKGluIHdoaWNoIGNhc2Ugd2UgZG9uJ3QgY2FyZSB3aGV0 aGVyIGFuIElSUSBoYXBwZW5zKS4KPiAKPiBbMV0gVGhhbmtzIHRvIEpha3ViIEtpY2nFhHNraSBm b3IgaGlzIGlucHV0IGFuZCBzaW1pbGFyIHBhdGNoLgo+IAo+IFNpZ25lZC1vZmYtYnk6IERhdmUg TWFydGluIDxEYXZlLk1hcnRpbkBhcm0uY29tPgoKU2lnbmVkLW9mZi1ieTogSmFrdWIgS2ljaW5z a2kgPGt1YmFraWNpQHdwLnBsPgoKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX18KbGludXgtYXJtLWtlcm5lbCBtYWlsaW5nIGxpc3QKbGludXgtYXJtLWtlcm5l bEBsaXN0cy5pbmZyYWRlYWQub3JnCmh0dHA6Ly9saXN0cy5pbmZyYWRlYWQub3JnL21haWxtYW4v bGlzdGluZm8vbGludXgtYXJtLWtlcm5lbAo= From mboxrd@z Thu Jan 1 00:00:00 1970 From: moorray3@wp.pl (Jakub =?UTF-8?B?S2ljacWEc2tp?=) Date: Mon, 30 Mar 2015 16:28:11 +0200 Subject: [PATCH v4 2/2] serial/amba-pl011: Refactor and simplify TX FIFO handling In-Reply-To: <1427468371-11915-3-git-send-email-Dave.Martin@arm.com> References: <1427468371-11915-1-git-send-email-Dave.Martin@arm.com> <1427468371-11915-3-git-send-email-Dave.Martin@arm.com> Message-ID: <20150330162811.3673482b@north> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, 27 Mar 2015 14:59:31 +0000, Dave Martin wrote: > Commit 734745c serial/amba-pl011: Activate TX IRQ passively > adds some unnecessary complexity and overhead in the form of > a softirq mechanism for transmitting in the absence of interrupts. > > After some discussion [1], this turns out to be unnecessary. > > This patch simplifies the code flow to reduce the reliance on > subtle behaviour and avoid fragility under future maintenance. > > To this end, the TX softirq mechanism is removed and instead > pl011_start_tx() will now simply stuff the FIFO until full > (guaranteeing future TX IRQs), or until there are no more chars > to write (in which case we don't care whether an IRQ happens). > > [1] Thanks to Jakub Kici?ski for his input and similar patch. > > Signed-off-by: Dave Martin Signed-off-by: Jakub Kicinski